MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Biotechnology and Bioengineering' source. Thu, 09 Feb 2012 14:07:50 +0100 http://www.medworm.com/index.php?rid=5635197&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24455 AbstractFor the aim of ex vivo engineering of functional tissue substitutes, Laser‐assisted BioPrinting (LaBP) is under investigation for the arrangement of living cells in predefined patterns. So far three‐dimensional arrangements of single or two‐dimensional patterning of different cell types have been presented. It has been shown that cells are not harmed by the printing procedure. We now demonstrate for the first time the 3D arrangement of vital cells by LaBP as multicellular grafts analogous to native archetype and the formation of tissue by these cells.For this purpose, fibroblasts and keratinocytes embedded in collagen were printed in 3D as a simple example for skin tissue. To study cell functions and tissue formation process in 3D, different characteristics such as cell local... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5635197 Fri, 27 Jan 2012 18:56:31 +0100 5635197 http://www.medworm.com/index.php?rid=5635201&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24451 In this study, a novel rotating algal biofilm reactor (RABR) was designed, built, and tested at bench (8 l), medium (535 l), and pilot (8,000 l) scales. The RABR was designed to operate in the photoautotrophic conditions of open tertiary wastewater treatment, producing mixed culture biofilms made up of algae and bacteria. Growth substrata were evaluated for attachment and biofilm formation, and an effective substratum was discovered. The RABR achieved effective nutrient reduction, with average removal rates of 2.1 g m−2 day−1 and 14.1 g m−2 day−1 for total dissolved phosphorus and total dissolved nitrogen, respectively. Biomass production ranged from 5.5 g m−2 day−1 at bench scale to as high as 31 g m−2 day−1 at pilot scale. An efficient spool harvesting tec... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5635201 Fri, 27 Jan 2012 05:00:00 +0100 5635201 http://www.medworm.com/index.php?rid=5635200&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24452 In this study, the relative roles of both signals in regard to cell adhesion, morphology and differentiation of C2C12 skeletal myoblasts were investigated. Grooved polystyrene substrates containing grooves with approximately 900 nm in width with 600 nm ridge spans and 665 nm in depth were conjugated with the cell adhesion peptide arginine‐glycine‐aspartic acid (RGD). RGD conjugation significantly enhanced the adhesion, growth and differentiation of C2C12 cells. On the other hand, anisotropic topography primarily directed the direction and alignment of myoblasts and myotubes. The results in this study provide information regarding the relative roles of chemical and topographic cues in musculoskeletal myogenesis, and are of interest to applications in muscle tissue engineering. B... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5635200 Fri, 27 Jan 2012 05:00:00 +0100 5635200 http://www.medworm.com/index.php?rid=5635199&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24453 AbstractUnderstanding how bioleaching systems respond to the availability of CO2 is essential to developing operating conditions that select for optimum microbial performance. Therefore, the effect of inlet gas and associated dissolved CO2 concentration on the growth, iron oxidation and CO2 fixation rates of pure cultures of Acidithiobacillus ferrooxidans and Leptospirillum ferriphilum was investigated in a batch stirred tank system. The minimum inlet CO2 concentrations required to promote the growth of At. ferrooxidans and L. ferriphilum were 25 ppm and 70 ppm, respectively, and corresponded to dissolved CO2 concentrations of 0.71 and 1.57 µM (at 30 °C and 37 °C, respectively). An actively growing culture of L. ferriphilum was able to maintain growth at inlet CO2 concentratio... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5635199 Fri, 27 Jan 2012 05:00:00 +0100 5635199 http://www.medworm.com/index.php?rid=5635198&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24454 AbstractThis work presents a characterization of the stoichiometry and kinetics of anaerobic batch growth of Saccharomyces cerevisiae at cultivation temperatures between 12 and 30 °C. To minimize the influence of the inoculum condition and ensure full adaptation to the cultivation temperature, the experiments were carried out in sequencing batch reactors. It was observed that the growth rate obtained in the first batch performed after each temperature shift was 10 to 30% different compared with the subsequent batches at the same temperature, which were much more reproducible. This indicates that the sequencing batch approach provides accurate and reproducible growth rate data.Data reconciliation was applied to the measured time patterns of substrate, biomass, carbon dioxide and byproducts... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5635198 Fri, 27 Jan 2012 05:00:00 +0100 5635198 http://www.medworm.com/index.php?rid=5635202&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24449 AbstractThe performance of microflotation, dispersed air flotation with microbubble clouds with bubble size about 50 microns, for algae separation using fluidic oscillation for microbubble generation is investigated. This fluidic oscillator converts continuous air supply into oscillatory flow with a regular frequency to generate bubbles of the scale of the exit pore. Bubble characterisation results showed that average bubble size generated under oscillatory air flow state was 86 µm, ∼ twice the size of the diffuser pore size of 38 µm. In contrast, continuous air flow at the same rate through the same diffusers yielded an average bubble size of 1059µm, 28 times larger than the pore size. Following microbubble generation, the separation of algal cells under fluidic oscillator genera... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5635202 Thu, 26 Jan 2012 05:00:00 +0100 5635202 http://www.medworm.com/index.php?rid=5603716&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24280 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603716 Wed, 18 Jan 2012 19:41:12 +0100 5603716 http://www.medworm.com/index.php?rid=5603715&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24279 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603715 Wed, 18 Jan 2012 19:41:11 +0100 5603715 http://www.medworm.com/index.php?rid=5603714&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24278 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603714 Wed, 18 Jan 2012 19:41:10 +0100 5603714 http://www.medworm.com/index.php?rid=5603713&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24277 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603713 Wed, 18 Jan 2012 19:41:09 +0100 5603713 http://www.medworm.com/index.php?rid=5603712&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24282 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603712 Wed, 18 Jan 2012 19:41:08 +0100 5603712 http://www.medworm.com/index.php?rid=5603693&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24439 AbstractMany enzymatic reactions are near‐equilibrium reactions. This often limits final yield and hence application of biocatalysed processes in the industrial production. The most widely applied strategy to overcome this issue is solvent selection. It must be underlined that measuring the equilibrium position experimentally is a difficult and time consuming procedure and any tool for predicting the solvent effect on the reaction equilibrium can be very valuable. The present work reports on the development of BESSICC, an algorithm to calculate the effect of medium composition on biocatalysed reactions equilibrium. It is based on COSMO‐RS calculation of activity coefficients of all the species in the reaction mixture and minimization of Gibbs free energy of the reaction. Starting from ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603693 Wed, 18 Jan 2012 19:39:18 +0100 5603693 http://www.medworm.com/index.php?rid=5656198&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24434 AbstractIn the present work the impact of large production scale was investigated for Bacillus megaterium expressing green fluorescent protein (GFP). Specifically designed scale‐down studies, mimicking the intermittent and continuous nutrient supply of large‐ and small‐scale processes, were carried out for this purpose. The recombinant strain revealed a 40% reduced GFP yield for the large‐scale conditions. In line with extended carbon loss via formation of acetate and carbon dioxide, this indicated obvious limitations in the underlying metabolism of B. megaterium under the large‐scale conditions. Quantitative analysis of intracellular amino acids via validated fast filtration protocols revealed that their level strongly differed between the two scenarios. During cultivation in la... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5656198 Tue, 17 Jan 2012 05:00:00 +0100 5656198 http://www.medworm.com/index.php?rid=5656197&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24448 AbstractMany secreted or cell surface proteins are post‐translationally modified by carbohydrate chains which are a primary source of heterogeneity. The Lec1 mutant, which is defective in Golgi N‐acetylglucosaminyltransferase I (GnTI) activity, produces relatively homogeneous Man5GlcNAc2 glycan modifications, and is widely used for various applications. To facilitate the investigation of GnTI, its Man5 glycan endproduct, and the impact of Man5 on effector function, the present study has established several novel Lec1 mutants in dhfr− CHO–DUKX cells through chemical mutagenesis and lectin selection. A total of nine clonal lines exhibiting the Lec1‐phenotype are characterized, six of which harbor non‐sense mutations leading to a truncated GnTI, and three (R415K, D291N, and P138L)... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5656197 Tue, 17 Jan 2012 05:00:00 +0100 5656197 http://www.medworm.com/index.php?rid=5656196&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24441 We present a novel analytical approach to describe biofilm processes considering continuum variation of both biofilm density and substrate effective diffusivity. A simple perturbation and matching technique was used to quantify biofilm activity using the steady‐state diffusion–reaction equation with continuum variable substrate effective diffusivity and biofilm density, along the coordinate normal to the biofilm surface. The procedure allows prediction of an effectiveness factor, η, defined as the ratio between the observed rate of substrate utilization (reaction rate with diffusion resistance) and the rate of substrate utilization without diffusion limitation. Main assumptions are that (i) the biofilm is a continuum, (ii) substrate is transferred by diffusion only and is consumed onl... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5656196 Tue, 17 Jan 2012 05:00:00 +0100 5656196 http://www.medworm.com/index.php?rid=5643682&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24443 This study assesses the effect of the granule size distribution on the performance of a granular sludge reactor in which autotrophic nitrogen removal is realized through one‐stage partial nitritation–anammox. A comparison is made between different approaches to deal with particle size distributions in one‐dimensional biofilm models, from the use of a single characteristic diameter to applying a multiple compartment model. The results show a clear impact on the conversion efficiency of the way in which particle size distribution is modeled, resulting from the effect of the granule size on the competition between nitrite oxidizing and anammox bacteria and from the interaction between granules of different sizes in terms of the exchange of solutes. Whereas the use of a uniform granule s... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5643682 Tue, 17 Jan 2012 05:00:00 +0100 5643682 http://www.medworm.com/index.php?rid=5624497&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24439 AbstractMany enzymatic reactions are near‐equilibrium reactions. This often limits final yield and hence application of biocatalyzed processes in the industrial production. The most widely applied strategy to overcome this issue is solvent selection. It must be underlined that measuring the equilibrium position experimentally is a difficult and time‐consuming procedure and any tool for predicting the solvent effect on the reaction equilibrium can be very valuable. The present work reports on the development of BESSICC, an algorithm to calculate the effect of medium composition on biocatalyzed reactions equilibrium. It is based on COSMO‐RS calculation of activity coefficients of all the species in the reaction mixture and minimization of Gibbs free energy of the reaction. Starting fro... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5624497 Tue, 17 Jan 2012 05:00:00 +0100 5624497 http://www.medworm.com/index.php?rid=5624496&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24435 AbstractWe used a pin‐on‐disc tribometer to measure the friction coefficient of both pristine and mechanically damaged cartilage samples in the presence of different lubricant solutions. The experimental set up maximizes the lubrication mechanism due to interstitial fluid pressurization. In phosphate buffer solution (PBS), the measured friction coefficient increases with the level of damage. The main result is that when poly(ethylene oxide) (PEO) or hyaluronic acid (HA) are dissolved in PBS, or when synovial fluid (SF) is used as lubricant, the friction coefficients measured for damaged cartilage samples are only slightly larger than those obtained for pristine cartilage samples, indicating that the surface damage is in part alleviated by the presence of the various lubricants. Among t... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5624496 Tue, 17 Jan 2012 05:00:00 +0100 5624496 http://www.medworm.com/index.php?rid=5624495&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24438 In this study, we developed an automated strategy to manufacture an enzyme BFC powered by glucose/O2. The bioanode consists of GOx enzyme and PQQ redox mediator adsorbed over night on MWCNTs then deposited by means of AC‐electrophoresis at 30 Hz and 160 Vp–p and, finally stabilized by electropolymerized polypyrrole. The biocathode is constructed from LAc enzyme and ABTS redox mediator adsorbed over night on MWCNTs, then electrophoretically deposited under AC‐electric field at 30 Hz and 160 Vp–p and, finally stabilized by electrodeposited polypyrrole. The BFC was studied under air in phosphate buffer solution pH 7.4 containing 10 mM glucose and in human serum with 5 mM glucose addition at the physiological temperature of 37°C. Under these conditions, the maximum power d... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5624495 Tue, 17 Jan 2012 05:00:00 +0100 5624495 http://www.medworm.com/index.php?rid=5603709&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24445 AbstractThe increasing demand for recombinant therapeutic proteins highlights the need to constantly improve the efficiency and yield of these biopharmaceutical products from mammalian cells, which is fully achievable only through proper understanding of cellular functioning. Towards this end, the current study exploited a combined metabolomics and in silico modeling approach to gain a deeper insight into the cellular mechanisms of Chinese hamster ovary (CHO) fed‐batch cultures. Initially, extracellular and intracellular metabolite profiling analysis shortlisted key metabolites associated with cell growth limitation within the energy, glutathione and glycerophospholipid pathways that have distinct changes at the exponential‐stationary transition phase of the cultures. In addition, biom... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603709 Tue, 17 Jan 2012 05:00:00 +0100 5603709 http://www.medworm.com/index.php?rid=5603708&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24446 AbstractA new methodology to use efficiently flue gases as CO2 source in the production of photosynthetic microorganisms is proposed. The CO2 is absorbed in an aqueous phase that is then regenerated by microalgae. Carbonated solutions could absorb up to 80% of the CO2 from diluted gas reaching TIC concentrations up to 2.0 g/l. The pH of the solution was maintained at 8.0‐10.0 by the bicarbonate/carbonate buffer, so it is compatible with biological regeneration. The absorption process was modeled and the kinetic parameters were determined. Anabaena sp. demonstrated to tolerate pH (8.0‐10.0) and TIC (up to 2.0 g/l) conditions imposed by the absorption step. Experiments of regeneration of the liquid phase demonstrated the feasibility of the overall process, converting CO2 into organic... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603708 Tue, 17 Jan 2012 05:00:00 +0100 5603708 http://www.medworm.com/index.php?rid=5603707&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24447 AbstractInoculum size strongly affects cell growth and lipid accumulation of microalgae, one of the most potential biodiesel feedstock, however, the metabolic mechanism(s) of the lipid biosynthesis upon inoculum size has not been fully explored yet. The effects of inoculum size on cell growth, lipid accumulation and metabolic changes of a green microalga Chlorella sorokiniana were investigated. In our experimental range of inoculum size, the productivity and the cetane number (CN) of fatty acid methyl esters (FAME) increased with increasing initial cell density, and the inoculum of 1 × 107 cells mL−1 pocessed much higher productivity (up to 2.02 fold) and cetane number (up to 1.19 fold) of the FAME than the others. A significant correlation between the metabolic profile and quan... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603707 Tue, 17 Jan 2012 05:00:00 +0100 5603707 http://www.medworm.com/index.php?rid=5603706&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24448 AbstractMany secreted or cell surface proteins are post‐translationally modified by carbohydrate chains which are a primary source of heterogeneity. The Lec1 mutant, which is defective in Golgi N‐acetylglucosaminyltransferase I (GnTI) activity, produces relatively homogeneous Man5GlcNAc2 glycan modifications, and is widely used for various applications. To facilitate the investigation of GnTI, its Man5 glycan endproduct, and the impact of Man5 on effector function, the present study has established several novel Lec1 mutants in dhfr‐ CHO‐DUKX cells through chemical mutagenesis and lectin selection. A total of nine clonal lines exhibiting the Lec1‐phenotype are characterized, six of which harbor non‐sense mutations leading to a truncated GnTI, and three (R415K, D291N, and P138L)... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603706 Tue, 17 Jan 2012 05:00:00 +0100 5603706 http://www.medworm.com/index.php?rid=5603705&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24450 AbstractNS0 cells require exogenous cholesterol for growth. The non‐GS cholesterol‐dependent NS0 host was treated with 5‐azacytidine (5azaC), a demethylation drug, and adapted to grow in cholesterol‐free, chemically‐defined medium. Within seven weeks, a stable, cholesterol‐independent NS0 host (NS0.CF) was obtained. The new NS0.CF host, as well as the original cholesterol auxotroph host, was transfected with the same mAb expression plasmid, and the top producing clone from both hosts were compared side‐by‐side in the enhanced platform fed‐batch cultures using chemically‐defined media. The NS0.CF derived clone significantly out‐performed the cholesterol‐dependent clone, with titer reaching 4.5 g/L vs 3.0 g/L, respectively, mainly due to higher specific productivi... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603705 Tue, 17 Jan 2012 05:00:00 +0100 5603705 http://www.medworm.com/index.php?rid=5603704&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24441 We present a novel analytical approach to describe biofilm processes considering continuum variation of both biofilm density and substrate effective diffusivity. A simple perturbation and matching technique was used to quantify biofilm activity using the steady‐state diffusion‐reaction equation with continuum variable substrate effective diffusivity and biofilm density, along the coordinate normal to the biofilm surface. The procedure allows prediction of an effectiveness factor, η, defined as the ratio between the observed rate of substrate utilization (reaction rate with diffusion resistance) and the rate of substrate utilization without diffusion limitation. Main assumptions are that (i) the biofilm is a continuum, (ii) substrate is transferred by diffusion only and is consumed onl... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603704 Tue, 17 Jan 2012 05:00:00 +0100 5603704 http://www.medworm.com/index.php?rid=5603703&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24442 AbstractThe use of glycine betaine combined with hyperosmolality is known to be an efficient means for achieving high protein production in recombinant Chinese hamster ovary (rCHO) cells. In order to understand the intracellular events and identify the key factors in rCHO cells cultivated with glycine betaine under hyperosmotic conditions, two‐dimensional differential in‐gel electrophoresis (2D‐DIGE) followed by mass spectrometric analysis was applied. Differentially expressed 19 protein spots were selected and 16 different kinds of proteins were successfully identified. The identified proteins were associated with cellular metabolism (PEPCK, GAPDH, and PK), cellular architecture (β‐tubulin and β‐actin), protein folding (GRP78 and OSP94), mRNA processing (Rbm34, ACF, and IPMK),... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603703 Tue, 17 Jan 2012 05:00:00 +0100 5603703 http://www.medworm.com/index.php?rid=5603702&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24443 This study assesses the effect of the granule size distribution on the performance of a granular sludge reactor in which autotrophic nitrogen removal is realized through one‐stage partial nitritation‐anammox. A comparison is made between different approaches to deal with particle size distributions in one‐dimensional biofilm models, from the use of a single characteristic diameter to applying a multiple compartment model. The results show a clear impact on the conversion efficiency of the way in which particle size distribution is modelled, resulting from the effect of the granule size on the competition between nitrite oxidizing and anammox bacteria and from the interaction between granules of different sizes in terms of the exchange of solutes. Whereas the use of a uniform granule ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603702 Tue, 17 Jan 2012 05:00:00 +0100 5603702 http://www.medworm.com/index.php?rid=5603701&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24444 AbstractWe study the role of nano‐scale cues in controlling neuronal growth. We use photolithography to fabricate substrates with repeatable line‐pattern ridges of nano‐scale heights. We find that neuronal processes, which are of micron size, have strong interactions with ridges even as low as 10 nm. The interaction between the neuronal process and the ridge leads to a deflection of growth direction and a preferred alignment with the ridges. The interaction strength clearly depends on the ridges' height. For 25 nm ridges approximately half of the neuronal processes are modified, while at 100 nm the majority of neurites change their original growth direction post interaction. In addition, the effect on growth correlates with the incoming angle between the neuronal process and th... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603701 Tue, 17 Jan 2012 05:00:00 +0100 5603701 http://www.medworm.com/index.php?rid=5603700&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24440 In this study, we have adopted a different approach whereby flows are redirected throughout the bioreactor along channels patterned in the porous scaffold to yield shear stress distributions that are optimized for uniformity centered on a target value. A topology optimization algorithm coupled to computational fluid dynamics simulations was devised to this end. The channel topology in the porous scaffold was varied using a combination of genetic algorithm and fuzzy logic. The method is validated by experiments using magnetic resonance imaging (MRI) readouts of the flow field. Biotechnol. Bioeng. © 2012 Wiley Periodicals, Inc. (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603700 Tue, 17 Jan 2012 05:00:00 +0100 5603700 http://www.medworm.com/index.php?rid=5603699&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24433 AbstractNumerical simulations and experimental validation were performed to understand the effects of hydrodynamics on pellet formation and cellulase production by filamentous T. reesei. The constructed model combined a steady‐state multiple reference frame (MRF) approach describing mechanical mixing, oxygen mass transfer, and non‐Newtonian flow field with a transient sliding mesh approach and kinetics of oxygen consumption, pellet formation, and enzyme production. The model was experimentally validated at various agitation speeds in a two‐impeller Rushton turbine fermentor. Results from simulation and experimentation showed that higher agitation speeds led to increases in the pellet diameter and the proportion of pelletized (versus filamentous) forms of the biomass. It also led to i... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603699 Tue, 17 Jan 2012 05:00:00 +0100 5603699 http://www.medworm.com/index.php?rid=5603698&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24434 AbstractIn the present work the impact of large production scale was investigated for Bacillus megaterium expressing green fluorescent protein (GFP). Specifically designed scale‐down studies, mimicking the intermittent and continuous nutrient supply of large and small scale processes, were carried out for this purpose. The recombinant strain revealed a 40% reduced GFP yield for the large scale conditions. In line with extended carbon loss via formation of acetate and carbon dioxide, this indicated obvious limitations in the underlying metabolism of B. megaterium under the large scale conditions. Quantitative analysis of intracellular amino acids via validated fast filtration protocols revealed that their level strongly differed between the two scenarios. During cultivation in large‐sca... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603698 Tue, 17 Jan 2012 05:00:00 +0100 5603698 http://www.medworm.com/index.php?rid=5603697&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24435 AbstractWe used a pin‐on‐disc tribometer to measure the friction coefficient of both pristine and mechanically damaged cartilage samples in the presence of different lubricant solutions. The experimental set up maximizes the lubrication mechanism due to interstitial fluid pressurization. In phosphate buffer solution (PBS), the measured friction coefficient increases with the level of damage. The main result is that when poly(ethylene oxide) (PEO) or hyaluronic acid (HA) are dissolved in PBS, or when synovial fluid (SF) is used as lubricant, the friction coefficients measured for damaged cartilage samples are only slightly larger than those obtained for pristine cartilage samples, indicating that the surface damage is in part alleviated by the presence of the various lubricants. Among t... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603697 Tue, 17 Jan 2012 05:00:00 +0100 5603697 http://www.medworm.com/index.php?rid=5603696&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24436 In this study, we performed genome sequencing, assembly and annotation analysis of A. balhimycina and further used these annotated data to reconstruct a genome‐scale metabolic model for the organism. Here we generated an almost complete A. balhimycina genome sequence comprising 10,562,587 base pairs assembled into 2,153 contigs. The high GC‐genome (∼69%) includes 8,585 open reading frames (ORFs). We used our integrative toolbox called SEQTOR for functional annotation and then integrated annotated data with biochemical and physiological information available for this organism to reconstruct a genome‐scale metabolic model of A. balhimycina. The resulting metabolic model contains 583 ORFs as protein encoding genes (7% of the predicted 8,585 ORFs), 407 EC numbers, 647 metabolites and 1... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603696 Tue, 17 Jan 2012 05:00:00 +0100 5603696 http://www.medworm.com/index.php?rid=5603695&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24437 AbstractChemotaxis toward chemical pollutants provides a mechanism for bacteria to migrate to locations of high contamination, which may improve the effectiveness of bioremediation. A microfluidic device was designed to mimic the dissolution of an organic‐phase contaminant from a single pore into a larger macropore representing a preferred pathway for microorganisms that are carried along by groundwater flow. The glass windows of the microfluidic device allowed direct image analysis of bacterial distributions within the vicinity of the organic contaminant. Concentrations of chemotactic bacteria P. putida F1 near the organic/aqueous interface were 25% greater than those of a nonchemotactic mutant in the vicinity of toluene for a fluid velocity of 0.5 m/d. For E. coli responding to pheno... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603695 Tue, 17 Jan 2012 05:00:00 +0100 5603695 http://www.medworm.com/index.php?rid=5603694&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24438 In this study, we developed an automated strategy to manufacture an enzyme BFC powered by glucose/O2. The bioanode consists of GOx enzyme and PQQ redox mediator adsorbed over night on MWCNTs then deposited by means of AC‐electrophoresis at 30 Hz and 160 Vp‐p and, finally stabilized by electropolymerized polypyrrole. The biocathode is constructed from LAc enzyme and ABTS redox mediator adsorbed over night on MWCNTs, then electrophoretically deposited under AC‐electric field at 30 Hz and 160 Vp‐p and, finally stabilized by electrodeposited polypyrrole. The BFC was studied under air in phosphate buffer solution pH 7.4 containing 10 mM glucose and in human serum with 5 mM glucose addition at the physiological temperature of 37 °C. Under these conditions, the maximum power dens... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603694 Tue, 17 Jan 2012 05:00:00 +0100 5603694 http://www.medworm.com/index.php?rid=5568572&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24430 This study investigated the effect of flow rate and voltage on size and uniformity of the hydrogel microspheres produced via submerged electrospray combined with UV photopolymerization. In addition, the mechanical properties and cell survival within microspheres was studied. A poly(vinyl alcohol) (PVA) macromer solution was sprayed in sunflower oil under flow rates between 1‐100µl/min and voltages 0‐10kV. The modes of spraying observed were similar to those previously reported for electrospraying in air. Spheres produced were smaller for lower flow rates and higher voltages and mean size could be tailored from 50‐1500µm. The microspheres exhibited a smooth, spherical morphology, did not aggregate and the compressive modulus of the spheres (350kPa) was equivalent to bulk PVA (312kPa... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568572 Sat, 07 Jan 2012 01:06:56 +0100 5568572 http://www.medworm.com/index.php?rid=5624494&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24426 AbstractA microfluidic system containing a chamber for heart tissue biopsies, perfused with Krebs–Henseleit buffer containing glucose and antibiotic (KHGB) using peristaltic pumps and continuously stimulated, was used to evaluate tissue viability under redox‐magnetohydrodynamics (redox‐MHD) conditions. Redox‐MHD possesses unique capabilities to control fluid flow using ionic current from oxidation and reduction processes at electrodes in a magnetic field, making it attractive to fine‐tune fluid flow around tissues for “tissue‐on‐a‐chip” applications. The manuscript describes a parallel setup to study two tissue samples simultaneously, and 6‐min static incubation with Triton X100. Tissue viability was subsequently determined by assaying perfusate for lactate dehydrogen... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5624494 Wed, 04 Jan 2012 05:00:00 +0100 5624494 http://www.medworm.com/index.php?rid=5603710&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24424 In this study, we employed a combined computational modeling and experimental approach to examine how the scaffold mean pore size influences cell attachment morphology and subsequently impacts upon cell deformation and detachment when subjected to fluid‐flow. Cell detachment from osteoblast‐seeded collagen–GAG scaffolds was evaluated experimentally across a range of scaffold pore sizes subjected to different flow rates and exposure times in a perfusion bioreactor. Cell detachment was found to be proportional to flow rate and inversely proportional to pore size. Using this data, a theoretical model was derived that accurately predicted cell detachment as a function of mean shear stress, mean pore size, and time. Computational modeling of cell deformation in response to fluid flow show... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5603710 Wed, 04 Jan 2012 05:00:00 +0100 5603710 http://www.medworm.com/index.php?rid=5592713&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24427 Abstract2,3‐Butanediol is an important compound that can be used in many areas, especially as a platform chemical and liquid fuel. But traditional 2,3‐butanediol producing microorganisms, such as Klebsiella pneumonia and K. xoytoca, are pathogens and they can only ferment sugars at 37°C. Here, we reported a newly developed Bacillus licheniformis. A protoplast transformation system was developed and optimized for this organism. With this transformation method, a marker‐less gene deletion protocol was successfully used to knock out the ldh gene of B. licheniformis BL1 and BL3. BL1 was isolated earlier from soil for lactate production and it was further evolved to BL3 for xylose utilization. Combined with pH and aeration control, ldh mutant BL5 and BL8 can efficiently ferment glucose a... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5592713 Wed, 04 Jan 2012 05:00:00 +0100 5592713 http://www.medworm.com/index.php?rid=5568585&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24431 AbstractIn HIV infections, homoeostasis of T‐cells is dysregulated such that there is a depletion of CD4+ T‐cells and a progressive loss of naïve CD4+ and CD8+ T‐cells. Methodologies that can improve the function of some or all of these cells will likely enhance immune responsiveness in HIV infection. Interleukin‐7 (IL‐7) is a cytokine that has been shown to be critical in homeostatic expansion of naïve CD8+ and CD4+ cells in lymphopenic hosts, as well as regulating effector T‐cell to memory T‐cell transition and memory T‐cell homeostasis. In animal studies and clinical trials, repeated injections of IL‐7 are used to boost both CD4+ and CD8+ cell counts. Daily injections, however, are painful, inconvenient, and provide a frequent route for pathogen entry. We developed a... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568585 Wed, 04 Jan 2012 05:00:00 +0100 5568585 http://www.medworm.com/index.php?rid=5568584&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24432 AbstractMesophilic glucuronidases are the most widely used reporters of gene expression in plants, but unsuitable as reporters in (hyper‐)thermophiles due their insufficient thermal stability. Here we present the native 66.8 kDa thermostable β‐glucuronidase of Sulfolobus solfataricus. The enzyme activity is characterized in a wide temperature range ideal for, but not limited to, in vivo genetic study of hyperthermophiles. As a proof of concept, we demonstrate its use as a reporter of gene expression in Sulfolobus, by monitoring a promoter fusion created with the β‐glucuronidase coding gene gusB and a copper‐responsive promoter. Biotechnol. Bioeng. © 2012 Wiley Periodicals, Inc. (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568584 Wed, 04 Jan 2012 05:00:00 +0100 5568584 http://www.medworm.com/index.php?rid=5568583&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24429 AbstractPolyethylene (PE) sheets were modified by radiation‐induced graft polymerization (RIGP) of an epoxy‐group containing monomer glycidyl methacrylate (GMA). The epoxy group of GMA was opened by introducing sodium sulfite (SS) and diethylamine (DEA) as representatives of negatively‐ and positively‐ charged functional groups, respectively. These modified surfaces by RIGP, termed GMA, SS and DEA sheets, were investigated to elucidate their effects on initial adhesion and subsequent biofilm formation of Escherichia coli. Initial adhesion test revealed that E. coli density and viability were governed by sheet surface electrostatic property: E. coli cell density on the DEA sheet was 23 times higher than that on the SS sheet after 8 hours incubation. The viability of E. coli cells ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568583 Wed, 04 Jan 2012 05:00:00 +0100 5568583 http://www.medworm.com/index.php?rid=5568581&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24421 AbstractCellular fates such as proliferation, differentiation and death are controlled by a variety of cytokine receptors, which are crucial in initiating downstream signaling cascades. To initiate signaling, the cytokine receptor cytoplasmic domain recruits specific signaling molecules with a range of tyrosine‐containing motifs. Thus, we postulate that it is possible to regulate signal transduction artificially by locating the tyrosine motif of interest into the intracellular domain of specific receptors. Construction of such artificial receptors was based on an anti‐fluorescein ScFv/c‐Mpl chimera (S‐Mpl). We selected several known tyrosine motifs from native cytokine receptors that strongly bind to their target molecule, and located them downstream of the JAK binding domain of S�... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568581 Wed, 04 Jan 2012 05:00:00 +0100 5568581 http://www.medworm.com/index.php?rid=5568580&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24422 AbstractA solvent‐free, chemoenzymatic reaction sequence for the enantioselective synthesis of β‐amino acid esters has been kinetically and thermodynamically characterized. The coupled sequence comprises a thermal aza‐Michael addition of cheap starting materials and a lipase catalyzed aminolysis for the kinetic resolution of the racemic ester. Excellent ee values of > 99% were obtained for the β‐amino acid ester at 60% conversion. Kinetic constants for the aza‐Michael addition were obtained by straightforward numerical intergration of second order rate equations and non‐linear fitting of the progress curves. A different strategy had to be devised for the biocatalytic reaction. Initially, a simplified Michaelis‐Menten model including product inhibition was developed f... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568580 Wed, 04 Jan 2012 05:00:00 +0100 5568580 http://www.medworm.com/index.php?rid=5568579&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24423 AbstractD‐Amino acid oxidase from Trigonopsis variabilis (TvDAO) is applied in industry for the synthesis of pharmaceutical intermediates. Because free TvDAO is extremely sensitive to exposure to gas‐liquid interfaces, biocatalytic processing is usually performed with enzyme immobilizates that offer enhanced stability under bubble aeration. We herein present an “Immobilization by Design” approach that exploits engineered charge complementarity between enzyme and carrier to optimize key features of the immobilization of TvDAO. A fusion protein between TvDAO and the positively charged module Zbasic2 was generated, and a corresponding oppositely charged carrier was obtained by derivatization of mesoporous glass with 3‐(trihydroxysilyl)‐1‐propane‐sulfonic acid. Using 250 mM N... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568579 Wed, 04 Jan 2012 05:00:00 +0100 5568579 http://www.medworm.com/index.php?rid=5568578&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24424 In this study we employed a combined computational modelling and experimental approach to examine how the scaffold mean pore size influences cell attachment morphology and subsequently impacts upon cell deformation and detachment when subjected to fluid‐flow. Cell detachment from osteoblast‐seeded collagen‐GAG scaffolds was evaluated experimentally across a range of scaffold pore sizes subjected to different flow‐rates and exposure times in a perfusion bioreactor. Cell detachment was found to be proportional to flow‐rate and inversely proportional to pore size. Using this data, a theoretical model was derived that accurately predicted cell detachment as a function of mean shear stress, mean pore size and time. Computational modelling of cell deformation in response to fluid flow ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568578 Wed, 04 Jan 2012 05:00:00 +0100 5568578 http://www.medworm.com/index.php?rid=5568577&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24425 AbstractMesenchymal stem cells (MSC) are emerging as a leading cellular therapy for a number of diseases. However, for such treatments to become available as a routine therapeutic option, efficient and cost‐effective means for industrial manufacture of MSC are required. At present, clinical grade MSC are manufactured through a process of manual cell culture in specialized cGMP facilities. This process is open, extremely labor intensive, costly, and impractical for anything more than a small number of patients. While it has been shown that MSC can be cultivated in stirred bioreactor systems using microcarriers, providing a route to process scale‐up, the degree of numerical expansion achieved has generally been limited. Furthermore, little attention has been given to the issue of primary... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568577 Wed, 04 Jan 2012 05:00:00 +0100 5568577 http://www.medworm.com/index.php?rid=5568576&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24426 AbstractA microfluidic system containing a chamber for heart tissue biopsies, perfused with Krebs‐Henseleit buffer containing glucose and antibiotic (KHGB) using a peristaltic pump and continuously stimulated, was used to evaluate tissue viability under redox‐magnetohydrodynamics (redox‐MHD) conditions. Redox‐MHD possesses unique capabilities to control fluid flow using ion current from oxidation and reduction processes at electrodes in a magnetic field, making it attractive to fine‐tune fluid flow around tissues for “tissue‐on‐a‐chip” applications. The manuscript describes a parallel setup to study two tissue samples simultaneously, and 6‐min static incubation with Triton X100. Tissue viability was subsequently determined by assaying perfusate for lactate dehydrogena... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568576 Wed, 04 Jan 2012 05:00:00 +0100 5568576 http://www.medworm.com/index.php?rid=5568575&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24427 Abstract2, 3‐butanediol is an important compound that can be used in many areas, especially as a platform chemical and liquid fuel. But traditional 2, 3‐butanediol producing microorganisms, such as Klebsiella pneumonia and K. xoytoca, are pathogens and they can only ferment sugars at 37°C. Here, we reported a newly developed Bacillus licheniformis. A protoplast transformation system was developed and optimized for this organism. With this transformation method, a marker‐less gene deletion protocol was successfully used to knock out the ldh gene of B. licheniformis BL1 and BL3. BL1 was isolated earlier from soil for lactate production and it was further evolved to BL3 for xylose utilization. Combined with pH and aeration control, ldh mutant BL5 and BL8 can efficiently ferment glucose... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568575 Wed, 04 Jan 2012 05:00:00 +0100 5568575 http://www.medworm.com/index.php?rid=5568573&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24428 AbstractClonally‐derived recombinant cell lines are highly desired to achieve consistent production of recombinant biotherapeutics. Despite repeated rounds of cloning by limiting dilution or single cell cloning, the resulting cell lines have often been observed to diverge, becoming a heterogeneous population and losing productivity over long term sub‐culturing. To understand the underlying molecular mechanisms, we developed quantitative polymerase chain reaction (qPCR) assays for the analysis of transgene copy number distribution in single recombinant cells isolated from Chinese Hamster Ovary (CHO) cell lines. Single cells were obtained by Fluorescence Activated Cell Sorting technology and lysed directly in 96‐well plates. qPCR assays were then applied to analyze the quantity and dis... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568573 Wed, 04 Jan 2012 05:00:00 +0100 5568573 http://www.medworm.com/index.php?rid=5532979&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24418 AbstractTransferred multi‐walled carbon nanotube (MWCNT)‐modified platinum thin‐film immunosensing electrode material was engineered on a glass substrate and fabricated a fully‐integrated electrochemical three‐electrode system for monitoring Legionella pneumophila. The transferred MWCNT film was treated with oxygen plasma to improve its electrochemical response and electrical conductivity. We voltammetrically characterized and optimized the electrochemical performance of the fabricated electrode for direct detection of Legionella pneumophila‐specific peptidoglycan‐associated lipoprotein (PAL) and maltose binding protein (MBP) peptidoglycan‐associated lipoprotein (MBP‐PAL) fusion. The latter, as an intermediate product to yield the former, has important roles in the growth... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5532979 Fri, 23 Dec 2011 07:48:25 +0100 5532979 http://www.medworm.com/index.php?rid=5532981&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24420 AbstractThe microbial production of free fatty acids and reduced derivatives is an attractive process for the renewable production of diesel fuels. Towards this goal, a plasmid‐free strain of Escherichia coli was engineered to produce free fatty acids by integrating three copies of a thioesterase gene from Umbellularia californica (BTE) under the control of an inducible promoter onto the chromosome. In batch culture, the resulting strain produced identical titers to a previously reported strain that expressed the thioesterase from a plasmid. The growth rate, glucose consumption rate, and free fatty acid production rate of this strain were studied in continuous cultivation under carbon limitation. The highest yield of free fatty acid on glucose was observed at a dilution rate of 0.05 h−... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5532981 Thu, 22 Dec 2011 05:00:00 +0100 5532981 http://www.medworm.com/index.php?rid=5532980&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24419 AbstractThe present work is initiated to investigate whether a defined culture comprising a mixture of three yeast species, Kluyveromyces marxianus, Saccharomyces cerevisiae and Pichia stipitis can ferment a mixture of sugars to produce bioethanol at rates higher than those achieved by pure cultures of the same. For this purpose, we develop models of single species based on the hybrid cybernetic model framework, and simulate fermentations in the mixed culture by combining individual models. An underlying assumption is that the behavior of each species is determined only by the common environment independently of the presence and metabolism of other species. Model performance is thoroughly assessed using the experimental data available in the literature. The dynamic behavior of mixed cultur... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5532980 Thu, 22 Dec 2011 05:00:00 +0100 5532980 http://www.medworm.com/index.php?rid=5576529&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24417 AbstractMost biomass pretreatment processes for monosaccharide production are run at low‐solid concentration (<10 wt%) and use significant amounts of chemical catalysts. Biphasic CO2–H2O mixtures could provide a more sustainable pretreatment medium while using high‐solid contents. Using a stirred reactor for high solids (40 wt%, biomass water mixture) biphasic CO2–H2O pretreatment of lignocellulosic biomass allowed us to explore the effects of particle size and mixing on mixed hardwood and switchgrass pretreatment. Subsequently, a two‐temperature stage pretreatment was introduced. After optimization, a short high‐temperature stage at 210°C (16 min for hardwood and 1 min for switchgrass) was followed by a long low‐temperature stage at 160°C for 60 min. Glucan to... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5576529 Wed, 21 Dec 2011 05:00:00 +0100 5576529 http://www.medworm.com/index.php?rid=5532984&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24415 AbstractMicroRNAs (miRNAs) are small, non‐coding RNAs that regulate multiple aspects of cell physiology. The differential expression of conserved miRNAs in two Chinese hamster ovary (CHO) cell lines producing recombinant proteins was examined relative to the CHO‐K1 cell line. A total of 190 conserved CHO miRNAs were identified through homology with known human and rodent miRNAs. More than 80% of these miRNAs showed differential expression in recombinant CHO cell lines. The small RNA sequencing data was analyzed in context of the CHO‐K1 genome to examine miRNA organization and develop sequence‐specific miRNA resources for CHO cells. The identification and characterization of CHO miRNAs will facilitate the use of miRNA tools in cell line engineering efforts to improve product yield a... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5532984 Wed, 21 Dec 2011 05:00:00 +0100 5532984 http://www.medworm.com/index.php?rid=5532983&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24417 AbstractMost biomass pretreatment processes for monosaccharide production are run at low‐solid concentration (<10 wt%) and use significant amounts of chemical catalysts. Biphasic CO2‐H2O mixtures could provide a more sustainable pretreatment medium while using high‐solid contents. Using a stirred reactor for high solids (40 wt%, biomass water mixture) biphasic CO2‐H2O pretreatment of lignocellulosic biomass allowed us to explore the effects of particle size and mixing on mixed hardwood and switchgrass pretreatment. Subsequently, a two‐temperature stage pretreatment was introduced. After optimization, a short high‐temperature stage at 210°C for 16 min with hardwood and 1 min with switchgrass was followed by a long low‐temperature stage at 160°C for 60 min. Gluca... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5532983 Wed, 21 Dec 2011 05:00:00 +0100 5532983 http://www.medworm.com/index.php?rid=5532982&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24416 AbstractCoexpression analysis is a powerful, widely used methodology for the investigation of underlying patterns in gene expression data. This “guilt‐by‐association” approach aims to find groups of genes with closely correlated expression profiles. Observation of these consistent correlations across phenotypically diverse samples indicates that these genes have a shared function. We have recently described the application of weighted gene coexpression network analysis (WGCNA) to a 295 sample production CHO cell line microarray dataset and elucidated groups of genes related to growth rate and cell specific productivity (Qp). In this manuscript we present the CHO gene coexpression database, a web‐based system, designed specifically for researchers in the CHO community to provide u... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5532982 Wed, 21 Dec 2011 05:00:00 +0100 5532982 http://www.medworm.com/index.php?rid=5512126&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24414 AbstractVariants of the Thermoascus aurantiacus Eg1 enzyme with higher catalytic efficiency than wild‐type were obtained via site‐directed mutagenesis. Using a rational mutagenesis approach based on structural bioinformatics and evolutionary analysis, two positions (F16S and Y95F) were identified as priority sites for mutagenesis. The mutant and parent enzymes were expressed and secreted from Pichia pastoris and the single site mutants F16S and Y95F showed 1.7‐ and 4.0‐ fold increases in kcat and 1.5‐ and 2.5‐fold improvements in hydrolytic activity on cellulosic substrates, respectively, while maintaining thermostability. Similar to the parent enzyme, the two variants were active between pH 4.0– 8.0 and showed optimal activity at temperature 70°C at pH 5.0. The purified enz... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512126 Sat, 17 Dec 2011 07:20:03 +0100 5512126 http://www.medworm.com/index.php?rid=5512131&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24409 AbstractYeast Saccharomyces cerevisiae has become an attractive cell factory for production of commodity and speciality chemicals and proteins, such as industrial enzymes and pharmaceutical proteins. Here we evaluate most important expression factors for recombinant protein secretion: we chose two different proteins (insulin precursor (IP) and α‐amylase), two different expression vectors (POTud plasmid and CPOTud plasmid) and two kinds of leader sequences (the glycosylated alpha factor leader and a synthetic leader with no glycosylation sites). We used IP and α‐amylase as representatives of a simple protein and a multi‐domain protein, as well as a non‐glycosylated protein and a glycosylated protein, respectively. The genes coding for the two recombinant proteins were fused indepe... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512131 Fri, 16 Dec 2011 05:00:00 +0100 5512131 http://www.medworm.com/index.php?rid=5512130&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24410 AbstractThe manufacture of enveloped virus, particularly retroviral and lentiviral vectors, faces the challenge of low titers that are aggravated under serum deprivation culture conditions. Also, the scarce knowledge on the biochemical pathways related with virus production is still limiting the design of rational strategies for improved production yields. This work describes the adaptation to serum deprivation of two human RV packaging cell lines, 293 FLEX and Te Fly and its effects on lipid biosynthetic pathways and infectious vector production. Total lipid content as well as cellular cholesterol were quantified and lipid biosynthesis was assessed by 13C‐NMR spectroscopy; changes in gene expression of lipid biosynthetic enzymes were also evaluated.The effects of adaptation to serum dep... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512130 Fri, 16 Dec 2011 05:00:00 +0100 5512130 http://www.medworm.com/index.php?rid=5512129&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24411 AbstractThe naturally existing microbial hosts can rarely satisfy industrial requirements, thus there has always been an intense effort in strain engineering to meet the needs of these bioprocesses. Here in this work, we want to prove the concept that engineering global transcription factor cAMP receptor protein (CRP) of E. coli can improve cell phenotypes. CRP is one of the global regulatory proteins that can regulate the transcription of over 400 genes in E. coli. The target phenotype in this study is strain osmotolerance. Amino acid mutations were introduced to CRP by either error‐prone PCR or DNA shuffling, and the random mutagenesis libraries were subjected to enrichment selection under NaCl stress. Five CRP mutants (MT1 − MT5) were selected from the error‐prone PCR librarie... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512129 Fri, 16 Dec 2011 05:00:00 +0100 5512129 http://www.medworm.com/index.php?rid=5512128&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24412 This report describes a new approach for fabricating micro‐channels within three‐dimensional electrospun constructs. These key features serve to mimic the fascicular architecture and fibrous extracellular matrix found in native nerve. Both electrospun fibers and multi‐channeled structure nerve guides have become areas of increasing interest for their beneficial roles in nerve repair. However, to the best of our knowledge, this is the first report of a guide that incorporates both. Multiple parallel channels provide a greater number of defined paths and increased surface area compared to cylindrical guides. Additionally, the fibrous nature of electrospun fibers permits better mass transport than solid‐walled constructs. The flexible fabrication scheme allows tailoring of nerve guide... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512128 Fri, 16 Dec 2011 05:00:00 +0100 5512128 http://www.medworm.com/index.php?rid=5512127&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24413 In this study, we constructed a stable producer line (LV‐MGFP) for synthesizing DC‐SIGN‐targeted HIV‐1‐based LVs (DC‐LVs) encoding green fluorescent protein (GFP) by a concatemeric array transfection technique. We demonstrated that the established stable clones could routinely produce vector supernatants with titers above 107 transduction units per milliliter (TU/mL) during a continuous 3‐month cell passage. The producer cells were also capable of generating similar titers of DC‐LVs in serum‐free medium. Moreover, the addition of 1‐deoxymannojirimycin (DMJ) enabled the producer cells to manufacture DC‐LVs with both improved titers and enhanced potency to evoke antigen‐specific CD8+ T cell responses in mice. The stable lines could accommodate the replacement of the i... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512127 Fri, 16 Dec 2011 05:00:00 +0100 5512127 http://www.medworm.com/index.php?rid=5500951&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24274 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500951 Wed, 14 Dec 2011 08:27:40 +0100 5500951 http://www.medworm.com/index.php?rid=5500950&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24273 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500950 Wed, 14 Dec 2011 08:27:38 +0100 5500950 http://www.medworm.com/index.php?rid=5500949&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24272 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500949 Wed, 14 Dec 2011 08:27:37 +0100 5500949 http://www.medworm.com/index.php?rid=5500948&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24271 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500948 Wed, 14 Dec 2011 08:27:36 +0100 5500948 http://www.medworm.com/index.php?rid=5500947&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24276 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500947 Wed, 14 Dec 2011 08:27:34 +0100 5500947 http://www.medworm.com/index.php?rid=5500943&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24406 AbstractIn this paper, we describe a hydrophobic interaction chromatography (HIC) method to remodel the carbohydrates on recombinant human β‐glucocerebrosidase (GCR) and the use of hydroxyl ethyl starch (HES) an ethylated starch polymer, to improve this process. GCR is a therapeutic protein used in the treatment of Gaucher disease, a life threatening condition in which patients lack sufficient functional levels of this enzyme. Gaucher disease is the most common inherited lysosomal storage disorder resulting in hepatomegaly, splenomegaly and bone and lung pathology due to the accumulation of glucosylceramide in the lysosomes of macrophages (Beutler and Grabowski 2001). The oligosaccharide remodeling of GCR, performed on HIC using three enzymes that remove sugars, increases macrophage upt... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500943 Wed, 14 Dec 2011 08:26:08 +0100 5500943 http://www.medworm.com/index.php?rid=5549518&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24407 We describe cloning of the single‐chain antibody sc528, which binds to the extracellular domain of the epidermal growth factor receptor (EGFR), from the parental monoclonal antibody and incorporation of a LPETGG tag sequence. Utilizing recombinant SrtA, we demonstrate successful incorporation of biotin from GGG‐biotin onto sc528. EGFR is an important cancer target and is over‐expressed in human tumor tissues and cancer lines, such as the A431 epithelial carcinoma cells. SrtA‐biotinylated sc528 specifically bound EGFR expressed on A431 cells, but not negative control lines. Similarly, when sc528 was labeled with fluorescein we observed antigen‐specific labeling. The ability to introduce functionality into recombinant antibodies in a controlled, site‐specific manner has applicati... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5549518 Wed, 14 Dec 2011 05:00:00 +0100 5549518 http://www.medworm.com/index.php?rid=5549517&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24401 This article is the first to report tensile test data specific to the centimeter scale using moist biofilm/sediment composite materials; the strain (ε)–stress (σ) relationships permit quantification of the elasticity (Young's modulus, E) and cohesive strength of each specimen. Specifically, we compare the mechanical strength of cyanobacterial biofilm‐only samples to that of biofilm cultured over sediment samples (glass beads or natural sands of d ∼ 1 mm) for up to 8 weeks. The range of tensile strength (1,288–3,283 Pa) for composite materials was up to three times higher than previous tensile tests conducted at smaller scale on mixed culture biofilm [Ohashi et al. (1999) Water Sci Technol 39:261–268], yet of similar range to cohesive strength values recorded on return a... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5549517 Wed, 14 Dec 2011 05:00:00 +0100 5549517 http://www.medworm.com/index.php?rid=5512138&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24401 AbstractBiofilms in marine and fluvial environments can comprise strong bacterial and diatom mats covering large areas of the bed and act to bind sediments. In this case the bed material becomes highly resistant to shear stresses applied by the overlying fluid motion and detachment, when it does occur, is manifest in patches of biofilm of the order cm2 being entrained into the flow. This paper is the first to report tensile test data specific to the centimeter scale using moist biofilm/sediment composite materials; the strain (ε) ‐ stress (σ) relationships permit quantification of the elasticity (Young's modulus, E) and cohesive strength of each specimen. Specifically, we compare the mechanical strength of cyanobacterial biofilm‐only samples to that of biofilm cultured over sediment ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512138 Wed, 14 Dec 2011 05:00:00 +0100 5512138 http://www.medworm.com/index.php?rid=5512137&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24402 This study describes the engineering of Escherichia coli towards the overproduction of the organophosphohydrolase (OpdA) from A. radiobacter at the surface of polyester inclusions. The OpdA was N‐terminally fused via a designed linker region to the C‐terminus of polyester inclusion‐forming enzyme PhaC of Ralstonia eutropha. The PhaC‐L‐OpdA fusion protein was overproduced by using the strong T7 promoter and when coexpressed with genes phaA (encoding β‐ketothiolase) and phaB (encoding acetoacetyl‐CoA reductase) from R. eutropha this led to formation of polyester inclusion abundantly displaying OpdA. These OpdA beads showed organophosphohydrolase activity of 1,840 U/g wet polyester beads or 4412 U/g protein. Steady state kinetics revealed that when compared with free OpdA t... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512137 Wed, 14 Dec 2011 05:00:00 +0100 5512137 http://www.medworm.com/index.php?rid=5512136&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24403 AbstractElucidation of the chemical logic of life is one of the grand challenges in biology, and essential to the progress of the upcoming field of synthetic biology. Treatment of microbial cells explicitly as a “chemical” species in controlled reaction (growth) environments has allowed fascinating discoveries of elemental formulae of a few species that have guided the modern views on compositions of a living cell. Application of mass and energy balances on living cells has proved to be useful in modeling of bioengineering systems, particularly in deriving optimized media compositions for growing microorganisms to maximize yields of desired bio‐derived products by regulating intra‐cellular metabolic networks. In this work, application of elemental mass balance during growth of Magn... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512136 Wed, 14 Dec 2011 05:00:00 +0100 5512136 http://www.medworm.com/index.php?rid=5512135&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24405 AbstractDevelopment of versatile and flexible assembly systems for fabrication of functional hybrid nanomaterials with well‐defined hierarchical and spatial organization is of a significant importance in practical nanobiotechnology applications. Here we demonstrate a bio‐enabled self‐assembly technique for fabrication of multi‐layered protein and nanometallic assemblies utilizing a modular gold‐binding (AuBP1) fusion tag. To accomplish the bottom‐up assembly we first genetically fused the AuBP1 peptide sequence to the C'‐terminus of maltose‐binding protein (MBP) using two different linkers to produce MBP‐AuBP1 hetero‐functional constructs. Using various spectroscopic techniques, Surface Plasmon Resonance (SPR) and Localized Surface Plasmon (LSPR), we verified the except... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512135 Wed, 14 Dec 2011 05:00:00 +0100 5512135 http://www.medworm.com/index.php?rid=5512134&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24408 AbstractGold nanorods (GNRs) have emerged as promising nanomaterials for biosensing, imaging, photothermal treatment and therapeutic delivery for several diseases, including cancer. We have generated poly(amino ether)‐functionalized gold nanorods (PAE‐GNRs) using a layer‐by‐layer deposition approach; polymers from a poly(amino ether) library recently synthesized in our laboratory were employed to generate the PAE‐GNR assemblies. PAE‐GNR assemblies demonstrate long‐term colloidal stability as well as the capacity to bind plasmid DNA by means of electrostatic interactions. Sub‐toxic concentrations of PAE‐GNRs were employed to deliver plasmid DNA to prostate cancer cells in vitro. PAE‐GNRs generated using 1,4C‐1,4Bis, a cationic polymer from our laboratory demonstrated s... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512134 Wed, 14 Dec 2011 05:00:00 +0100 5512134 http://www.medworm.com/index.php?rid=5512133&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24404 AbstractMetabolically active resting (i.e., non‐growing) bacterial cells have a high potential in redox cofactor‐dependent biotransformations. Where growing cells require carbon and energy for biomass production, resting cells can potentially exploit their metabolism more efficiently for redox biocatalysis allowing higher specific activities and product yields on energy source. Here, the potential of resting recombinant E. coli containing the styrene monooxygenase StyAB was investigated for enantioselective styrene epoxidation in a two‐liquid phase setup. Resting cells indeed showed two‐fold higher specific activities as compared to growing cells in a similar setup. However, product formation rates decreased steadily resulting in lower final product concentrations. The low intrinsi... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512133 Wed, 14 Dec 2011 05:00:00 +0100 5512133 http://www.medworm.com/index.php?rid=5512132&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24407 We describe cloning of the single‐chain antibody sc528, which binds to the extracellular domain of the epidermal growth factor receptor (EGFR), from the parental monoclonal antibody and incorporation of a LPETGG tag sequence. Utilizing recombinant Sortase A, we demonstrate successful incorporation of biotin from GGG‐biotin onto sc528. EGFR is an important cancer target and is over‐expressed in human tumor tissues and cancer lines such as the A431 epithelial carcinoma cells. Sortase A‐biotinylated sc528 specifically bound EGFR expressed on A431 cells, but not negative control lines. Similarly, when sc528 was labeled with fluorescein we observed antigen‐specific labeling. The ability to introduce functionality into recombinant antibodies in a controlled, site‐specific manner ha... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5512132 Wed, 14 Dec 2011 05:00:00 +0100 5512132 http://www.medworm.com/index.php?rid=5482779&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24398 We report the identification of a novel small open reading frame in Escherichia coli. The sORF (called iroK) encodes a 21 amino‐acid peptide, which when translated confers a 133% (c.a. 20 g/L) increase in resistance to 3‐hydroxypropionic acid. We show that IroK conferred tolerance is additive to previously identified tolerance mechanisms involving relief of inhibited metabolism, yet does not involve altered 3HP transport. This result demonstrates the continued surprises that microbial genomes hold and emphasize the importance of comprehensive discovery methods in future strain and metabolic engineering efforts. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5482779 Thu, 08 Dec 2011 07:48:31 +0100 5482779 http://www.medworm.com/index.php?rid=5568588&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24398 We report the identification of a novel small open reading frame in Escherichia coli. The sORF (called iroK) encodes a 21 amino cid peptide, which when translated confers a 133% (ca. 20 g/L) increase in resistance to 3‐hydroxypropionic acid. We show that iroK conferred tolerance is additive to previously identified tolerance mechanisms involving relief of inhibited metabolism, yet does not involve altered 3‐HP transport. This result demonstrates the continued surprises that microbial genomes hold and emphasize the importance of comprehensive discovery methods in future strain and metabolic engineering efforts. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5568588 Wed, 07 Dec 2011 05:00:00 +0100 5568588 http://www.medworm.com/index.php?rid=5500945&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24395 This article describes a comparative survey of biodiesel production and conversion yields of biodiesel via alkaline transesterification of acylglycerols extracted from the microalgae Thalassiosira pseudonana and Phaeodactylum tricornutum, grown under silicate or nitrate limitation, and that of model vegetable oils: soybean, and rapeseed oil. Acylglycerols were extracted with n‐hexane and the total yield per biomass was determined by gravimetric assay. Under our conditions, the total acylglycerol yield from the microalgae studied was 13–18% of total dry weight. The biodiesel samples were analyzed using gas chromatography–flame ionization detector to determine quantitative information of residual glycerol, mono‐, di‐, and tri‐acylglycerol concentrations in the biodiesel. All of t... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500945 Wed, 07 Dec 2011 05:00:00 +0100 5500945 http://www.medworm.com/index.php?rid=5482782&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24395 AbstractAlgal biofuels are a growing interest worldwide due to their potential in terms of sustainable greenhouse gas displacement and energy production. This paper describes a comparative survey of biodiesel production and conversion yields of biodiesel via alkaline transesterification of acylglycerols extracted from the microalgae Thalassiosira pseudonana and Phaeodactylum tricornutum, grown under silicate or nitrate limitation, and that of model vegetable oils: soybean, and rapeseed oil. Acylglycerols were extracted with n‐hexane and the total yield per biomass was determined by gravimetric assay. Under our conditions, the total acylglycerol yield from the microalgae studied was 13–18% of total dry weight. The biodiesel samples were analyzed using gas chromatography‐flame ionizati... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5482782 Wed, 07 Dec 2011 05:00:00 +0100 5482782 http://www.medworm.com/index.php?rid=5482781&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24400 AbstractWe have developed a hematopoietic co‐culture system using the hollow fiber bioreactor (HFBR) as a potential in vitro bone marrow model for evaluating leukemia. Supporting stroma using HS‐5 cells was established in HFBR system and the current bioprocess configuration yielded an average glucose consumption of 640 mg/day and an average protein concentration of 6.40 mg/mL in the extracapillary space over 28 days. Co‐culture with erythroleukemia K562 cells was used as a model for myelo‐leukemic cell proliferation and differentiation. Two distinct localizations of K562 cells (loosely adhered and adherent cells) were identified and characterized after two weeks. The HFBR co‐culture resulted in greater leukemic cell expansion (3130 folds vs. 43 folds) compared to a standard tissu... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5482781 Wed, 07 Dec 2011 05:00:00 +0100 5482781 http://www.medworm.com/index.php?rid=5482780&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24399 AbstractWe previously reported the development of a simple, user‐friendly, and versatile 384 hanging drop array plate for 3D spheroid culture and the importance of utilizing 3D cellular models in anti‐cancer drug sensitivity testing. The 384 hanging drop array plate allows for high‐throughput capabilities and offers significant improvements over existing 3D spheroid culture methods. To allow for practical 3D cell‐based high‐throughput screening and enable broader use of the plate, we characterize the robustness of the 384 hanging drop array plate in terms of assay performance and demonstrate the versatility of the plate. We find that the 384 hanging drop array plate performance is robust in fluorescence‐ and colorimetric‐based assays through z‐factor calculations. Finally, ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5482780 Wed, 07 Dec 2011 05:00:00 +0100 5482780 http://www.medworm.com/index.php?rid=5473468&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24375 This study demonstrates that iPSC expansion and differentiation conditions can be prospectively specified to guide the enhanced production of target cells in a scale‐free directed differentiation system. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc.We combine quantitative assessment of process inefficiencies during differentiation of pluripotent stem cells towards definitive endoderm fate with investigations of the underlying cellular mechanisms and new technologies for aggregate size control. This has resulted in an improved understanding of the biological foundations of this process, a thirty‐six fold increase in yield of target cells, and a generalizable template for future study and optimization of pluripotent stem cell differentiation bioprocesses. (Source: Biotechnology and... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5473468 Fri, 02 Dec 2011 05:00:00 +0100 5473468 http://www.medworm.com/index.php?rid=5453904&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24397 AbstractThree‐dimensional (3D) tumor models have been established in various microfluidic systems for drug delivery and resistance studies in vitro. However, one of the main drawbacks of these models is non‐uniform distribution of cells, leaving regions with very low cell density within the 3D structures. As a result, molecular diffusion in the cell compartments is faster than that observed in solid tumors. To solve this problem, we developed a new technique for preparation of 3D tumor models in vitro. It was based on a microfluidic device containing three parallel channels separated by narrowly‐spaced posts. Tumor cells were loaded into the central channel at high density. To test the system, B16.F10 melanoma cells were perfusion‐cultured overnight and the resulting 3D structure w... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453904 Tue, 29 Nov 2011 07:41:35 +0100 5453904 http://www.medworm.com/index.php?rid=5500944&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24396 AbstractInfluence of mechanical characteristics and matrix architecture of substrates used in cell culture is an important issue to tissue engineering. Chitosan‐based materials have been processed into porous structures, injectable gels and membranes, and are investigated to regenerate various tissues. However, the effect of these structures on cell growth and matrix production in accordance with each of the differing scaffolds has not been examined. We investigated the influence of porous structures, hydrogels, and membranes on the growth of normal human fibroblasts and their matrix production in a serum‐free system. We used chitosan alone and in combination with gelatin. Injectable hydrogels were prepared using 2‐glycerol phosphate. From the same solution, porous scaffolds and memb... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5500944 Mon, 28 Nov 2011 05:00:00 +0100 5500944 http://www.medworm.com/index.php?rid=5453917&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24396 AbstractInfluence of mechanical characteristics and matrix architecture of substrates used in cell culture is an important issue to tissue engineering. Chitosan‐based materials have been processed into porous structures, injectable gels and membranes and are investigated to regenerate various tissues. However, the effect of these structures on cell growth and matrix production in accordance with each of the differing scaffolds has not been examined. We investigated the influence of porous structures, hydrogels and membranes on the growth of normal human fibroblasts and their matrix production in a serum‐free system. We used chitosan alone and in combination with gelatin. Injectable hydrogels were prepared using 2‐glycerol phosphate. From the same solution, porous scaffolds and membra... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453917 Mon, 28 Nov 2011 05:00:00 +0100 5453917 http://www.medworm.com/index.php?rid=5453916&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24394 AbstractTo establish a production platform for recombinant proteins in rice suspension cells, we first constructed a Gateway‐compatible binary T‐DNA destination vector. It provided a reliable and effective method for the rapid directional cloning of target genes into plant cells through Agrobacterium‐mediated transformation. We used the approach to produce mouse granulocyte‐macrophage colony‐stimulating factor (mGM‐CSF) in a rice suspension cell system. The promoter for the αAmy3 amylase gene, which is induced strongly by sugar depletion, drove the expression of mGM‐CSF. The resulting recombinant protein was fused with the αAmy3 signal peptide and was secreted into the culture medium. The production of rice‐derived mGM‐CSF (rmGM‐CSF) was scaled up successfully in a 2�... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453916 Mon, 28 Nov 2011 05:00:00 +0100 5453916 http://www.medworm.com/index.php?rid=5453915&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24393 AbstractUnderstanding the cellular responses caused by metabolic stress is crucial for the design of robust fed‐batch bioprocesses that maximize the expression of recombinant proteins. Chinese hamster ovary (CHO) cells were investigated in chemically defined, serum‐free cultures yielding 107 cells/mL and up to 500 mg/L recombinant tissue plasminogen activator (t‐PA). Upon glutamine depletion increased autophagosome formation and autophagic flux were observed, along with decreased proliferation and high viability. Higher lysosomal levels correlated with decreased productivity. Chemical inhibition of autophagy with 3‐methyl adenine (3‐MA) increased the t‐PA yield by 2.8‐fold. Autophagy‐related MAP1LC3 and LAMP2 mRNA levels increased continuously in all cultures. Analysis ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453915 Mon, 28 Nov 2011 05:00:00 +0100 5453915 http://www.medworm.com/index.php?rid=5453914&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24392 AbstractThe production of biopharmaceuticals from mammalian cell culture is hindered by apoptosis, which is the primary cause of cell death in these cultures. As a tool for optimization of culture yield, this paper presents a population‐based model describing the progression of apoptosis in a monoclonal antibody‐producing Chinese hamster ovary (CHO) cell culture. Because monoclonal antibody production does not cease when apoptosis begins, the model was designed to incorporate subpopulations at various stages in the progression of apoptosis. The model was validated against intracellular measurements of caspase activity as well as cell density, nutrient levels, and toxic metabolites. Since the specific details of apoptotic mechanisms have not been elucidated in this cell line, we employe... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453914 Mon, 28 Nov 2011 05:00:00 +0100 5453914 http://www.medworm.com/index.php?rid=5453913&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24391 AbstractThis paper reports the optimization of a perfusion bioreactor system previously reported by us (Chouinard et al., 2009). The implementation of a proportional‐integral (PI) controller algorithm to control oxygen concentration and pH is presented and discussed. P and I values used by the controller were first estimated using a First‐Order‐Plus‐Dead‐Time (FOPDT, Matlab Simulink) and then tuned manually. A new gas exchanger design compatible with the PI controller was introduced and validated to decrease interaction between the injected gases and overall inertia of the system. The gas exchanger was used to adjust both pH and dissolved oxygen concentration. This new bioreactor system allowed real‐time PI control over pH and dissolved oxygen concentration at different flow ra... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453913 Mon, 28 Nov 2011 05:00:00 +0100 5453913 http://www.medworm.com/index.php?rid=5453912&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24390 AbstractThe ability for a biofilm to grow and function is critically dependent on the nutrient availability, and this in turn is dependent on the structure of the biofilm. This relationship is therefore an important factor influencing biofilm maturation. Nutrient transport in bacterial biofilms is complex; however, mathematical models that describe the transport of particles within biofilms have made three simplifying assumptions: the effective diffusion coefficient (EDC) is constant, the EDC is that of water, and/or the EDC is isotropic. Using a Monte Carlo simulation, we determined the EDC, both parallel to and perpendicular to the substratum, within 131 real, single species, three‐dimensional biofilms that were constructed from confocal laser scanning microscopy images. Our study show... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453912 Mon, 28 Nov 2011 05:00:00 +0100 5453912 http://www.medworm.com/index.php?rid=5453911&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24389 AbstractLactate has long been regarded as one of the key metabolites of mammalian cell cultures. High levels of lactate have clear negative impacts on cell culture processes, and therefore, a great amount of efforts have been made to reduce lactate accumulation and/or to induce lactate consumption in the later stage of cultures. However, there is virtually no report on the impact of lactate depletion after initial accumulation. In this work, we observed that glucose uptake rate dropped over 50% at the onset of lactate consumption, and that catabolism of alanine due to lactate depletion led to ammonium accumulation. We explored the impact of feeding lactate as well as pyruvate to the cultures. In particular, a strategy was employed where CO2 was replaced by lactic acid for culture pH contro... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453911 Mon, 28 Nov 2011 05:00:00 +0100 5453911 http://www.medworm.com/index.php?rid=5453910&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24388 AbstractBacteria modulate glycoside hydrolase expression in response to the changes in the composition of lignocellulosic biomass. The response of switchgrass‐adapted thermophilic bacterial consortia to perturbation with a variety of biomass substrates was characterized to determine if bacterial consortia also responded to changes in biomass composition. Incubation of the switchgrass‐adapted consortia with these alternative substrates produced shifts in glycoside hydrolase activities and bacterial community composition. Substantially increased endoglucanase activity was observed upon incubation with microcrystalline cellulose and trifluororacetic acid‐pretreated switchgrass. In contrast, culturing the microbial consortia with ionic liquid‐pretreated switchgrass increased xylanase a... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453910 Mon, 28 Nov 2011 05:00:00 +0100 5453910 http://www.medworm.com/index.php?rid=5453909&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24387 AbstractThe aim of this work was the development of a feed‐control for a succinic acid production fed‐batch process. The performed batch trials indicated a correlation between succinic acid production and base consumption pH control. Based on the metabolism of A. succiniciproducens, a theoretical correlation between base consumption and glucose feed was established and proved in cultivation trials. With the established fed‐batch process, the succinic acid yield could be increased to 0.875 (g/g glucose) in comparison to batch processes (0.60) with similar glucose concentrations.Additionally the results indicate that the osmolarity of the medium has a significant influence on succinic acid production. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and Bioeng... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453909 Mon, 28 Nov 2011 05:00:00 +0100 5453909 http://www.medworm.com/index.php?rid=5453908&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24386 AbstractMulti‐stage and single‐stage enzymatic hydrolysis of cellulose (Avicel PH‐101) was conducted to investigate individual factors that affect the rate‐reducing kinetics of enzymatic hydrolysis. Understanding factors affecting enzymatic hydrolysis of Avicel will help improve hydrolysis of various biomasses. Product inhibition, enzyme deactivation, and the changes of substrate are potential factors that can affect the hydrolysis efficiency of Avicel. Multi‐stage enzymatic hydrolysis resulted in 36.9% and 25.4% higher carbohydrate conversion as compared to a single‐stage enzymatic hydrolysis with an enzyme loading of 5 and 20 FPU/g in a 96 h reaction. However, a decline in carbohydrate conversion of 1.6% and 2.6% was observed through each stage with 5 and 20 FPU/g, respecti... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453908 Mon, 28 Nov 2011 05:00:00 +0100 5453908 http://www.medworm.com/index.php?rid=5453907&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24385 AbstractAlkaline hydrogen peroxide (AHP) has several attractive features as a pretreatment in the lignocellulosic biomass‐to‐ethanol pipeline. Here, the feasibility of scaling‐up the AHP process and integrating it with enzymatic hydrolysis and fermentation was studied. Corn stover (1 kg) was subjected to AHP pretreatment, hydrolyzed enzymatically, and the resulting sugars fermented to ethanol. The AHP pretreatment was performed at 0.125 g H2O2/g biomass, 22°C, and atmospheric pressure for 48 h with periodic pH readjustment. The enzymatic hydrolysis was performed in the same reactor following pH neutralization of the biomass slurry and without washing. After 48 h, glucose and xylose yields were 75% and 71% of the theoretical maximum. Sterility was maintained during pretreatme... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453907 Mon, 28 Nov 2011 05:00:00 +0100 5453907 http://www.medworm.com/index.php?rid=5453906&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24384 AbstractThe twin arginine translocation (Tat) pathway occurs naturally in E. coli and has the distinct ability to translocate folded proteins across the inner membrane of the cell. It has the potential to export commercially useful proteins that cannot be exported by the ubiquitous Sec pathway.To better understand the bioprocess potential of the Tat pathway, this paper addresses the fermentation and downstream processing performances of E. coli strains with a wild‐type Tat system exporting the over‐expressed substrate protein FhuD. These were compared to strains cell‐engineered to over‐express the Tat pathway, since the native export capacity of the Tat pathway is low. This low capacity makes the pathway susceptible to saturation by over‐expressed substrate proteins, and can resu... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453906 Mon, 28 Nov 2011 05:00:00 +0100 5453906 http://www.medworm.com/index.php?rid=5453905&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24383 AbstractThe characterisation of host cell protein (HCP) content during the production of therapeutic recombinant proteins is an important aspect in the drug development process. Despite this, key components of the HCP profile and how this changes with processing has not been fully investigated. Here we have investigated the supernatant HCP profile at different times throughout culture of a null and model GS‐CHO monoclonal antibody producing mammalian cell line grown in fed‐batch mode. Using 2D‐PAGE and LC‐MS/MS we identify a number of intracellular proteins (e.g. protein disulphide isomerise; elongation factor 2; calreticulin) that show a significant change in abundance relative to the general increase in HCP concentration observed with progression of culture. Those HCPs that showe... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5453905 Mon, 28 Nov 2011 05:00:00 +0100 5453905 http://www.medworm.com/index.php?rid=5437123&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24378 AbstractThe growth of iron‐oxidizing bacteria, generally regarded as obligate microaerophilic at neutral pH conditions, has been reported in a wide range of environments, including engineered systems for drinking water production. This research focused on intensively aerated trickling filters treating deep anaerobic and subsurface aerated groundwater. The two systems, each comprising groundwater abstraction and trickling filtration, were monitored over a period of nine months. Gallionella spp. were quantified by qPCR with specifically designed 16S rRNA primers and identified directly in the environmental samples using clone libraries with the same primers. In addition, enrichments in gradient tubes were evaluated after DGGE separation with general bacterial primers. No other iron‐oxidi... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5437123 Wed, 23 Nov 2011 07:09:45 +0100 5437123 http://www.medworm.com/index.php?rid=5417230&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24268 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417230 Thu, 17 Nov 2011 21:53:12 +0100 5417230 http://www.medworm.com/index.php?rid=5417229&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24267 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417229 Thu, 17 Nov 2011 21:53:11 +0100 5417229 http://www.medworm.com/index.php?rid=5417228&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24266 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417228 Thu, 17 Nov 2011 21:53:09 +0100 5417228 http://www.medworm.com/index.php?rid=5417227&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24265 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417227 Thu, 17 Nov 2011 21:53:08 +0100 5417227 http://www.medworm.com/index.php?rid=5417226&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24270 (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417226 Thu, 17 Nov 2011 21:53:07 +0100 5417226 http://www.medworm.com/index.php?rid=5417213&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24374 AbstractThe Chinese hamster genome database (http://www.chogenome.org/) is an online resource for the Chinese hamster (Cricetulus griseus) and Chinese hamster ovary (CHO) cell communities. CHO cells are important for biomedical research and are widely used in industry for the production of biopharmaceuticals. The genome of the CHO‐K1 cell line was recently sequenced and the CHO community has developed an online resource to facilitate accessibility of the genomic data and the development of genomic tools. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417213 Thu, 17 Nov 2011 21:51:23 +0100 5417213 http://www.medworm.com/index.php?rid=5437124&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24371 In this study, the thermostability of CalB was improved through the introduction of a new disulfide bridge. Analysis of the B‐factors of residue pairs in CalB wild type (CalB‐WT) followed by simple flexibility analysis of residues in CalB‐WT and its designated mutants using FIRST server were newly proposed to enhance the selective power of two computational tools (MODIP and DbD v1.20) to predict the possible disulfide bonds in proteins for the enhancement of thermostability. Five residue pairs (A162‐K308, N169‐F304, Q156‐L163, S50‐A273, and S239C‐D252C) were chosen and the respective amino acid residues were mutated to cysteine. In the results, CalB A162C‐K308C showed greatly improved thermostability while maintaining its catalytic efficiency compared to that of CalB‐WT... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5437124 Thu, 17 Nov 2011 05:00:00 +0100 5437124 http://www.medworm.com/index.php?rid=5417224&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24379 AbstractDesigning and building multigene constructs is commonplace in synthetic biology. Yet functional successes at first attempts are rare because the genetic parts are not fully modular. In order to improve the modularity of transcription, we previously showed that transcription termination in vitro by bacteriophage T7 RNA polymerase could be made more efficient by substituting the standard, single, TΦ large (class I) terminator with adjacent copies of the Vesicular Stomatitis Virus (VSV) small (class II) terminator. However, in vitro termination at the downstream VSV terminator was less efficient than at the upstream VSV terminator, and multigene overexpression in vivo was complicated by unexpectedly inefficient VSV termination within E. coli cells. Here, we address hypotheses raised ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417224 Thu, 17 Nov 2011 05:00:00 +0100 5417224 http://www.medworm.com/index.php?rid=5417223&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24380 Abstractn‐Butanol was produced continuously in a two‐stage fermentor system with integrated product removal from a co‐feed of n‐butyric acid and glucose. Glucose was always required as a source of ATP and electrons for the conversion of n‐butyrate to n‐butanol and for biomass growth; for the latter it also served as a carbon source. The 1st stage generated metabolically active planktonic cells of Clostridium saccharoperbutylacetonicum strain N1‐4 that were continuously fed into the 2nd (production) stage; the volumetric ratio of the two fermentors was 1:10. n‐Butanol was removed continuously from the second stage via gas stripping. Implementing a two‐stage process was observed to dramatically dampen metabolic oscillations (i.e., periodical changes of solventogenic activit... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417223 Thu, 17 Nov 2011 05:00:00 +0100 5417223 http://www.medworm.com/index.php?rid=5417222&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24381 AbstractA 3D Biofilm model, appropriate for complex porous media support structures, is successfully modified such that non‐zero permeability of biofilms structures is enabled. A systematic study is then conducted into the influence of biofilm permeability on overall biomass growth rate. This reveals a significant influence at large biofilm concentrations; even when the permeability of the biomass is 1.25% of that of the free pore space, biomass accumulation increased by a factor of ∼3 over 40 hours. The effect is shown to be retained when allowing for biomass detachment or erosion as a consequence of adjacent velocity shear. We conclude that biofilm permeability should be included in biofilm models and that further experimental work is required to better describe the link between bi... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417222 Thu, 17 Nov 2011 05:00:00 +0100 5417222 http://www.medworm.com/index.php?rid=5417221&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24382 AbstractIschemia/reperfusion (I/R) injury is a considerable insult to skeletal muscle, often resulting in prolonged functional deficits. The purpose of the current study was to evaluate the controlled release of the pro‐regenerative growth factor, insulin‐like growth factor‐I (IGF‐I), from a biodegradable PEGylated fibrin gel matrix and the subsequent recovery of skeletal muscle from I/R. To accomplish this, the hind limbs of male Sprague‐Dawley rats were subjected to 2 hour tourniquet (TK)‐induced I/R then treated with saline, bolus IGF‐I (bIGF), PEGylated fibrin gel (PEG‐Fib), or IGF‐I conjugated PEGylated fibrin gel (PEG‐Fib‐IGF). Functional and histological evaluations were performed following 14 days of reperfusion, and muscles from 4‐day reperfusion animals we... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417221 Thu, 17 Nov 2011 05:00:00 +0100 5417221 http://www.medworm.com/index.php?rid=5417220&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24376 AbstractFourier transform infrared, attenuated total reflectance (FTIR‐ATR) spectroscopy, combined with partial least squares (PLS) regression, accurately predicted solubilization of plant cell‐wall constituents and NaOH consumption through pretreatment, and overall sugar productions from combined pretreatment and enzymatic hydrolysis. PLS regression models were constructed by correlating FTIR spectra of six raw biomasses (two switchgrass cultivars, big bluestem grass, a low‐impact, high‐diversity mixture of prairie biomasses, mixed hardwood, and corn stover), plus alkali loading in pretreatment, to nine dependent variables: glucose, xylose, lignin, and total solids solubilized in pretreatment; NaOH consumed in pretreatment; and overall glucose and xylose conversions and yields fro... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417220 Thu, 17 Nov 2011 05:00:00 +0100 5417220 http://www.medworm.com/index.php?rid=5417219&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24377 In this study, SPTFF technology was systematically evaluated for reducing process intermediate volumes from 2x to 10x with multiple mAbs and the impact of SPTFF on product quality, and process yield was analyzed. Finally, the potential fit into the typical 3‐column industry platform antibody purification process and its implementation in a commercial scale manufacturing facility were also evaluated. Our data indicates that using SPTFF to concentrate protein pools is a simple, flexible, and robust operation, which can be implemented at various scales to improve antibody purification process capacity. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417219 Thu, 17 Nov 2011 05:00:00 +0100 5417219 http://www.medworm.com/index.php?rid=5417218&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24370 AbstractWith the aim of understanding the contribution of enzymes to the cost of lignocellulosic biofuels, we constructed a technoeconomic model for the production of fungal cellulases. We found that the cost of producing enzymes was much higher than that commonly assumed in the literature. For example, the cost contribution of enzymes to ethanol produced by the conversion of corn stover was found to be $0.68/gal if the sugars in the biomass could be converted at maximum theoretical yields, and $1.47/gal if the yields were based on saccharification and fermentation yields that have been previously reported in the scientific literature. We performed a sensitivity analysis to study the effect of feedstock prices and fermentation times on the cost contribution of enzymes to ethanol price. We ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417218 Thu, 17 Nov 2011 05:00:00 +0100 5417218 http://www.medworm.com/index.php?rid=5417217&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24369 AbstractThe conversion of soluble uranyl ions (UO) by bacterial reduction to sparingly soluble uraninite (UO2(s)) is being studied as a way of immobilizing subsurface uranium contamination. Under anaerobic conditions, several known types of bacteria including iron and sulfate reducing bacteria have been shown to reduce U (VI) to U (IV). Experiments using a suspension of uraninite (UO2(s)) particles produced by Shewanella putrefaciens CN32 bacteria show a dependence of both longitudinal (T1) and transverse (T2) magnetic resonance (MR) relaxation times on the oxidation state and solubility of the uranium. Gradient echo and spin echo MR images were compared to quantify the effect caused by the magnetic field fluctuations (T2*) of the uraninite particles and soluble uranyl ions. Since the prec... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417217 Thu, 17 Nov 2011 05:00:00 +0100 5417217 http://www.medworm.com/index.php?rid=5417216&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24371 In this study, the thermostability of CalB was improved through the introduction of a new disulfide bridge. Analysis of the B‐factors of residue pairs in CalB wild type (CalB‐WT) followed by simple flexibility analysis of residues in CalB‐WT and its designated mutants using FIRST server were newly proposed to enhance the selective power of two computational tools (MODIP and DbD v1.20) to predict the possible disulfide bonds in proteins for the enhancement of thermostability. Five residue pairs (A162‐K308, N169‐F304, Q156‐L163, S50‐A273 and S239C‐D252C) were chosen and the respective amino acid residues were mutated to cysteine. In the results, CalB A162C‐K308C showed greatly improved thermostability while maintaining its catalytic efficiency compared to that of CalB‐WT.... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417216 Thu, 17 Nov 2011 05:00:00 +0100 5417216 http://www.medworm.com/index.php?rid=5417215&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24372 AbstractThe effect of dynamic mechanical shear and compression on the synthesis of human tissue‐engineered cartilage was investigated using a mechanobioreactor capable of simulating the rolling action of articular joints in a mixed fluid environment. Human chondrocytes seeded into polyglycolic acid (PGA) mesh or PGA–alginate scaffolds were precultured in shaking T‐flasks or recirculation perfusion bioreactors for 2.5 or 4 weeks prior to mechanical stimulation in the mechanobioreactor. Constructs were subjected to intermittent unconfined shear and compressive loading at a frequency of 0.05 Hz using a peak‐to‐peak compressive strain amplitude of 2.2% superimposed on a static axial compressive strain of 6.5%. The mechanical treatment was carried out for up to 2.5 weeks using a loa... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417215 Thu, 17 Nov 2011 05:00:00 +0100 5417215 http://www.medworm.com/index.php?rid=5417214&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24373 In this study, insulin secretion experiments were conducted with two hepatic cell lines (HepG2 and H4IIE) transduced with one of three adenoviruses expressing the insulin transgene and with a stably transfected recombinant intestinal cell line (GLUTag‐INS). Insulin secretion was stimulated by exposing the cells to glucose only (hepatic cells), meat hydrolysate only (GLUTag‐INS), or to a cocktail of the two secretagogues. It was found experimentally that the recombinant hepatic cells secreted insulin in a more sustained manner, whereas the recombinant intestinal cell line exhibited rapid insulin secretion kinetics upon stimulation. The insulin secretion profiles were computationally combined at different cell ratios to arrive at the combinatorial kinetics. Results indicate that combinat... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5417214 Thu, 17 Nov 2011 05:00:00 +0100 5417214 http://www.medworm.com/index.php?rid=5396504&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24368 AbstractPerfusion bioreactors have been used in different tissue engineering applications because of their consistent distribution of nutrients and flow‐induced shear stress within the tissue engineering scaffold. A widely used configuration uses a scaffold with a circular cross‐section enclosed within a cylindrical chamber and inlet and outlet pipes which are connected to the chamber on either side through which media is continuously circulated. However, fluid‐flow experiments and simulations have shown that the majority of the flow perfuses through the center. This pattern creates stagnant zones in the peripheral regions as well as in those of high flow rate near the inlet and outlet. This non‐uniformity of flow and shear stress, owing to a circular design, results in limited cel... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396504 Fri, 11 Nov 2011 07:52:41 +0100 5396504 http://www.medworm.com/index.php?rid=5437127&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24360 AbstractThe possibility of converting hydrogen to methane and simultaneous upgrading of biogas was investigated in both batch tests and fully mixed biogas reactor, simultaneously fed with manure and hydrogen. Batch experiments showed that hydrogen could be converted to methane by hydrogenotrophic methanogenesis with conversion of more than 90% of the consumed hydrogen to methane. The hydrogen consumption rates were affected by both (hydrogen partial pressure) and mixing intensity. Inhibition of propionate and butyrate degradation by hydrogen (1 atm) was only observed under high mixing intensity (shaking speed 300 rpm). Continuous addition of hydrogen (flow rate of 28.6 mL/(L/h)) to an anaerobic reactor fed with manure, showed that more than 80% of the hydrogen was utilized. The propi... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5437127 Tue, 08 Nov 2011 05:00:00 +0100 5437127 http://www.medworm.com/index.php?rid=5437125&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24363 This study fills this void by reporting novel butanoylated ManNAc analogs that are used by cells with greater efficiency and less cytotoxicity than the current “gold standard,” which are peracetylated compounds such as Ac4ManNAz. In particular, tributanoylated, N‐acetyl, N‐azido, and N‐levulinoyl ManNAc analogs with the high flux 1,3,4‐O‐hydroxyl pattern of butanoylation were compared with their counterparts having the pro‐apoptotic 3,4,6‐O‐butanoylation pattern. The results reveal that the ketone‐bearing N‐levulinoyl analog 3,4,6‐O‐Bu3ManNLev is highly apoptotic, and thus is a promising anti‐cancer drug candidate. By contrast, the azide‐bearing analog 1,3,4‐O‐Bu3ManNAz effectively labeled cellular sialoglycans at concentrations ∼3‐ to 5‐fold lower... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5437125 Tue, 08 Nov 2011 05:00:00 +0100 5437125 http://www.medworm.com/index.php?rid=5396512&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24366 AbstractDecolorization and mineralization of reactive dyes by intimately coupled TiO2‐photocatalysis and biodegradation (ICPB) on a novel TiO2‐coated biofilm carrier were investigated in a photocatalytic circulating‐bed biofilm reactor (PCBBR). Two typical reactive dyes – Reactive Black 5 (RB5) and reactive yellow 86 (RY86) – showed similar first‐order kinetics when being photocatalytically decolorized at low pH (∼4‐5) in batch experiments. Photocatalytic decolorization was inhibited at neutral pH in the presence of phosphate or carbonate buffer, presumably due to electrostatic repulsion from negatively charged surface sites on TiO2, radical scavenging by phosphate or carbonate, or both. Therefore, continuous PCBBR experiments were carried out at a low pH (∼ 4.5) to maint... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396512 Tue, 08 Nov 2011 05:00:00 +0100 5396512 http://www.medworm.com/index.php?rid=5396511&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24363 This study fills this void by reporting novel butanoylated ManNAc analogues that are used by cells with greater efficiency and less cytotoxicity than the current “gold standard,” which are peracetylated compounds such as Ac4ManNAz. In particular, tributanoylated, N‐acetyl, N‐azido, and N‐levulinoyl ManNAc analogues with the high flux 1,3,4‐O‐hydroxyl pattern of butanoylation were compared with their counterparts having the pro‐apoptotic 3,4,6‐O‐butanoylation pattern. The results reveal that the ketone‐bearing N‐levulinoyl analogue 3,4,6‐O‐Bu3ManNLev is highly apoptotic, and thus is a promising anti‐cancer drug candidate. By contrast, the azide‐bearing analogue 1,3,4‐O‐Bu3ManNAz effectively labeled cellular sialoglycans at concentrations ∼3 to 5‐fold ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396511 Tue, 08 Nov 2011 05:00:00 +0100 5396511 http://www.medworm.com/index.php?rid=5396510&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24364 AbstractModeling biotechnological processes is key to obtaining increased productivity and efficiency. Particularly crucial to successful modeling of such systems is the coupling of the physical transport phenomena and the biological activity in one model. We have applied a model for the expression of cellulosic enzymes by the filamentous fungus Trichoderma reesei and found excellent agreement with experimental data. The most influential factor was demonstrated to be viscosity and its influence on mass transfer. Not surprisingly, the biological model is also shown to have high influence on the model prediction. At different rates of agitation and aeration as well as head space pressure, we can predict the energy efficiency of oxygen transfer, a key process parameter for economical producti... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396510 Tue, 08 Nov 2011 05:00:00 +0100 5396510 http://www.medworm.com/index.php?rid=5396509&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24365 AbstractAlthough Chinese hamster ovary (CHO) cells, with their unique characteristics, have become a major workhorse for the manufacture of therapeutic recombinant proteins, one of the major challenges in CHO cell line generation is how to efficiently identify those rare, high producing clones among a large population of low and non‐productive clones. It is not unusual that several hundred individual clones need to be screened for the identification of a commercial clonal cell line with acceptable productivity and growth profile making the cell line appropriate for commercial application. This inefficiency makes the process of cell line generation both time consuming and laborious. Currently, there are two main CHO expression systems, dihydrofolate reductase (DHFR)‐based methotrexate (... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396509 Tue, 08 Nov 2011 05:00:00 +0100 5396509 http://www.medworm.com/index.php?rid=5396508&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24367 AbstractOne of the most important criteria for the successful manufacture of a therapeutic protein, e.g., an antibody) is to develop a mammalian cell line that maintains stability of production. Problems with process yield, lack of effective use of costly resources, and a possible delay in obtaining regulatory approval of the product may ensue otherwise. Therefore the stability of expression in a number of Chinese Hamster Ovary (CHO) derived production cell lines that were isolated using the Glutamine Synthetase (GS) selection system was investigated by defining a culture as unstable if the titer (which is a measure of productivity) of a cell line expressing an antibody or antibody‐fusion protein declined by 20‐30% or more as it underwent 55 population doublings. Using this criterion, ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396508 Tue, 08 Nov 2011 05:00:00 +0100 5396508 http://www.medworm.com/index.php?rid=5396507&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24360 AbstractThe possibility of converting hydrogen to methane and simultaneous upgrading of biogas was investigated in both batch tests and fully mixed biogas reactor, simultaneously fed with manure and hydrogen. Batch experiments showed that hydrogen could be converted to methane by hydrogenotrophic methanogenesis with conversion of more than 90% of the consumed hydrogen to methane. The hydrogen consumption rates were affected by both PH2 (hydrogen partial pressure) and mixing intensity. Inhibition of propionate and butyrate degradation by hydrogen (1 atm) was only observed under high mixing intensity (shaking speed 300 rpm). Continuous addition of hydrogen (flow rate of 28.6 mL/(Lh)) to an anaerobic reactor fed with manure, showed that more than 80% of the hydrogen was utilized. The prop... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396507 Tue, 08 Nov 2011 05:00:00 +0100 5396507 http://www.medworm.com/index.php?rid=5396506&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24361 In this study, a species of red marine microalgae, Porphyridium sp., was grown in three airlift column photobioreactors (i.e., draft tube column, bubble column, and split column). The physical properties of the culture medium, the local fluid dynamics and the photobioreactor performances were investigated and are reported in this part of the manuscript. Results indicate that the presence of microalgae considerably affected the local multiphase flow dynamics in the studied draft tube column. Results also show that the split column reactor works slightly better than the draft tube and the bubble columns due to the spiral flow pattern inside the reactor. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and Bioengineering) Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396506 Tue, 08 Nov 2011 05:00:00 +0100 5396506 http://www.medworm.com/index.php?rid=5396505&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24362 AbstractDynamic growth rate model has been developed to quantify the impact of hydrodynamics on the growth of photosynthetic microorganisms and to predict the photobioreactor performance. Rigorous verification of such reactor models however is rare in the literature. In this part of work, verification of a dynamic growth rate model developed in Luo and Al‐Dahhan (2004) was attempted using the experimental results reported in Part I of this work and results from literature. The irradiance distribution inside the studied reactor was also measured at different optical densities and successfully correlated by the Lambert‐Beer Law. When reliable hydrodynamic data were used, the dynamic growth rate model successfully predicted the algae's growth rate obtained in the experiments in both low a... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396505 Tue, 08 Nov 2011 05:00:00 +0100 5396505 http://www.medworm.com/index.php?rid=5374801&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24357 AbstractSolubility of cytochrome c, a typical heme protein, in a various ionic liquids has been analyzed. The solubility has been discussed with polarity parameters of the ionic liquids. Both hydrogen bond basicity and dipolarity/polarisability of the ionic liquids were confirmed to be influential factors to control the solubilization of cytochrome c. Polar ionic liquids such as 1‐butyl‐3‐methylimidazolium chloride and 1‐allyl‐3‐methylimidazolium chloride solubilized cytochrome c at 80 oC, and the dissolved cytochrome c was found to keep its redox activity in these ionic liquid. The redox response of the dissolved cytochrome c was detected in 1‐allyl‐3‐methylimidazolium chloride up to 140 oC. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and B... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5374801 Fri, 04 Nov 2011 17:40:57 +0100 5374801 http://www.medworm.com/index.php?rid=5404654&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24359 AbstractCYP51, a sterol 14α‐demethylase, is one of the key enzymes involved in sterol biosynthesis and requires electrons transferred from its redox partners. A unique CYP51 from Nocardia farcinica IFM10152 forms a distinct cluster with iron–sulfur containing NADPH‐P450 reductase (FprD) downstream of CYP51. Previously, sequence alignment of nine reductases from N. farcinica revealed that FprC, FprD, and FprH have an additional sequence at their N‐termini that has very high identity with iron–sulfur clustered ferredoxin G (FdxG). To construct an artificial self‐sufficient cytochrome P450 monooxygenase (CYP) with only FprD, CYP51, and iron–sulfur containing FprD were fused together with designed linker sequences. CYP51–FprD fusion enzymes showed distinct spectral properties ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5404654 Fri, 28 Oct 2011 04:00:00 +0100 5404654 http://www.medworm.com/index.php?rid=5396514&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24356 AbstractSynthetic biology and metabolic engineering are used to develop new strategies for producing valuable compounds ranging from therapeutics to biofuels in engineered microorganisms. When developing methods for high‐titer production cells, toxicity is an important element to consider. Indeed the production rate can be limited due to toxic intermediates or accumulation of byproducts of the heterologous biosynthetic pathway of interest. Conversely, highly toxic molecules are desired when designing antimicrobials. Compound toxicity in bacteria plays a major role in metabolic engineering as well as in the development of new antibacterial agents. Here, we screened a diversified chemical library of 166 compounds for toxicity in Escherichia coli. The dataset was built using a clustering al... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396514 Fri, 28 Oct 2011 04:00:00 +0100 5396514 http://www.medworm.com/index.php?rid=5396513&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24357 AbstractSolubility of cytochrome c, a typical heme protein, in a various ionic liquids has been analyzed. The solubility has been discussed with polarity parameters of the ionic liquids. Both hydrogen bond basicity and dipolarity/polarizability of the ionic liquids were confirmed to be influential factors to control the solubilization of cytochrome c. Polar ionic liquids such as 1‐butyl‐3‐methylimidazolium chloride and 1‐allyl‐3‐methylimidazolium chloride solubilized cytochrome c at 80°C, and the dissolved cytochrome c was found to keep its redox activity in these ionic liquids. The redox response of the dissolved cytochrome c was detected in 1‐allyl‐3‐methylimidazolium chloride up to 140°C. Biotechnol. Bioeng. © 2011 Wiley Periodicals, Inc. (Source: Biotechnology and ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396513 Fri, 28 Oct 2011 04:00:00 +0100 5396513 http://www.medworm.com/index.php?rid=5374805&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24356 AbstractSynthetic biology and metabolic engineering are used to develop new strategies for producing valuable compounds ranging from therapeutics to biofuels in engineered microorganisms. When developing methods for high‐titer production cells, toxicity is an important element to consider. Indeed the production rate can be limited due to toxic intermediates or accumulation of byproducts of the heterologous biosynthetic pathway of interest. Conversely, highly toxic molecules are desired when designing antimicrobials. Compound toxicity in bacteria plays a major role in metabolic engineering as well as in the development of new antibacterial agents. Here, we screened a diversified chemical library of 166 compounds for toxicity in Escherichia coli. The dataset was built using a clustering al... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5374805 Fri, 28 Oct 2011 04:00:00 +0100 5374805 http://www.medworm.com/index.php?rid=5374804&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24358 AbstractThe removal of analog impurities with a very small sample size presents a major challenge in the purification of high‐valued biochemicals such as those derived from fermentation or herbs. Ganoderic acid T (GA‐T), an antitumor drug candidate, is very difficult to purify from the mycelia of medicinal mushroom Ganoderma lucidum due to co‐purifying analog impurities. A novel pretreatment process with three consecutive chemical conversion steps, namely hydrolysis‐acetylation‐hydrolysis, was developed to convert two key analog impurities (7‐O‐ethyl GA‐O and GA‐Mk) to GA‐T. It increased the GA‐T amount in the 100g dried mycelia from the initial 0.444 g to 1.621 g after the pretreatment, representing an apparent yield of 365% for the pretreatment. If the yield bas... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5374804 Fri, 28 Oct 2011 04:00:00 +0100 5374804 http://www.medworm.com/index.php?rid=5374803&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24359 AbstractCYP51, a sterol 14α‐demethylase, is one of the key enzymes involved in sterol biosynthesis and requires electrons transferred from its redox partners. A unique CYP51 from Nocardia farcinica IFM10152 forms a distinct cluster with iron‐sulfur containing NADPH‐P450 reductase (FprD) downstream of CYP51. Previously, sequence alignment of nine reductases from N. farcinica revealed that FprC, FprD, and FprH have an additional sequence at their N‐termini that has very high identity with iron‐sulfur clustered ferredoxin G (FdxG). To construct an artificial self‐sufficient CYP with only FprD, CYP51 and iron‐sulfur containing FprD were fused together with designed linker sequences. CYP51‐FprD fusion enzymes showed distinct spectral properties of both flavoprotein and CYP. CYP... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5374803 Fri, 28 Oct 2011 04:00:00 +0100 5374803 http://www.medworm.com/index.php?rid=5374802&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24355 This report investigates the design of hydrogels that balance the requirements for supporting neurite growth with those requirements for promoting gene delivery. Enzymatically‐degradable PEG hydrogels encapsulating dorsal root ganglia explants, fibroblasts, and lipoplexes encoding nerve growth factor were gelled within channels that can physically guide neurite outgrowth. Transfection of fibroblasts increased with increasing concentration of Arg‐Gly‐Asp (RGD) cell adhesion sites and decreasing PEG content. The neurite length increased with increasing RGD concentration within 10% PEG hydrogels, yet was maximal within 7.5% PEG hydrogels at intermediate RGD levels. Delivering lipoplexes within the gel produced longer neurites than culture in NGF‐supplemented media or co‐culture with... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5374802 Fri, 28 Oct 2011 04:00:00 +0100 5374802 http://www.medworm.com/index.php?rid=5355114&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.23354 AbstractThe projected cost for the enzymatic hydrolysis of cellulosic biomass continues to be a barrier for the commercial production of liquid transportation fuels from renewable feedstocks. Predictive models for the kinetics of the enzymatic reactions will enable an improved understanding of current limitations, such as the slow‐down of the overall conversion rate, and may point the way for more efficient utilization of the enzymes in order to achieve higher conversion yields. A mechanistically based kinetic model for the enzymatic hydrolysis of cellulose was recently reported in Griggs et al. (2011) (Part I). In this article (Part II), the enzyme system is expanded to include solution‐phase kinetics, particularly cellobiose‐to‐glucose conversion by β‐glucosidase (βG), and no... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5355114 Thu, 27 Oct 2011 04:00:00 +0100 5355114 http://www.medworm.com/index.php?rid=5355113&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.23355 AbstractA mechanistically based kinetic model for the enzymatic hydrolysis of cellulosic biomass has been developed that incorporates the distinct modes of action of cellulases on insoluble cellulose polymer chains. Cellulose depolymerization by an endoglucanase (endoglucanase I, EGI) and an exoglucanase (cellobiohydrolase I, CBHI) is modeled using population‐balance equations, which provide a kinetic description of the evolution of a polydisperse distribution of chain lengths. The cellulose substrate is assumed to have enzyme‐accessible chains and inaccessible interior chains. EGI is assumed to randomly cleave insoluble cellulose chains. For CBHI, distinct steps for adsorption, complexation, processive hydrolysis, and desorption are included in the mechanistic description. Population�... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5355113 Thu, 27 Oct 2011 04:00:00 +0100 5355113 http://www.medworm.com/index.php?rid=5343387&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24354 This study examined the scale up of this process for treatment of water from a ClO and RDX contaminated aquifer in Cape Cod Massachusetts. A pilot‐scale upflow PBR (∼250‐L) was constructed with elemental sulfur and crushed oyster shell packing media. The reactor was inoculated with sulfur oxidizing ClO reducing cultures enriched from a wastewater seed. Sodium sulfite provided a good method of dissolved oxygen removal in batch cultures, but was found to promote the growth of bacteria that carry out sulfur disproportionation and sulfate reduction, which inhibited ClO reduction in the pilot system. After terminating sulfite addition, the PBR successfully removed 96% of the influent ClO in the groundwater at an empty bed contact time (EBCT) of 12 hours (effluent ClO of 4.2 µg L−... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5343387 Sun, 23 Oct 2011 22:52:58 +0100 5343387 http://www.medworm.com/index.php?rid=5343388&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.23350 AbstractCoupling an anaerobic digester to a microalgal culture has received increasing attention as an alternative process for combined bioenergy production and depollution. In this article, a dynamic model for anaerobic digestion of microalgae is developed with the aim of improving the management of such a coupled system. This model describes the dynamics of inorganic nitrogen and volatile fatty acids since both can lead to inhibition and therefore process instability. Three reactions are considered: Two hydrolysis–acidogenesis steps in parallel for sugars/lipids and for proteins, followed by a methanogenesis step. The proposed model accurately reproduces experimental data for anaerobic digestion of the freshwater microalgae Chlorella vulgaris with an organic loading rate of 1 gCOD L�... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5343388 Fri, 21 Oct 2011 04:00:00 +0100 5343388 http://www.medworm.com/index.php?rid=5330252&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24337 AbstractThe commercial development of ionic liquids (IL) to pretreat lignocellulose by dissolution of whole biomass and cellulose precipitation by addition of water is hindered by the absence of an effective technique to recover the lignin content of the biomass from the ionic liquid. Three organic solvents (ethyl acetate, 1,4‐dioxane and tetrahydrofuran) were studied for their ability to form a two‐liquid‐phase system with water and 1‐ethyl‐3‐methylimidazolium acetate ([C2mim][OAc], and for partitioning model lignins and lignin monomers between the two liquid phases. Ternary diagrams were obtained for three [C2mim][OAc]/organic solvent/water systems at 22°C. Partition coefficients were measured for several types of lignin in these three systems. Partition coefficients increas... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5330252 Wed, 19 Oct 2011 17:53:36 +0100 5330252 http://www.medworm.com/index.php?rid=5437126&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24337 AbstractThe commercial development of ionic liquids (ILs) to pretreat lignocellulose by dissolution of whole biomass and cellulose precipitation by addition of water is hindered by the absence of an effective technique to recover the lignin content of the biomass from the IL. Three organic solvents [ethyl acetate, 1,4‐dioxane, and tetrahydrofuran (THF)] were studied for their ability to form a two‐liquid‐phase system with water and 1‐ethyl‐3‐methylimidazolium acetate ([C2mim][OAc]), and for partitioning model lignins and lignin monomers between the two liquid phases. Ternary diagrams were obtained for three [C2mim][OAc]/organic solvent/water systems at 22°C. Partition coefficients were measured for several types of lignin in these three systems. Partition coefficients increase... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5437126 Wed, 19 Oct 2011 04:00:00 +0100 5437126 http://www.medworm.com/index.php?rid=5404653&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24350 AbstractBased on the general theoretical model developed in Part I of this work, a series of numerical simulations related to the in vitro proliferation kinetics of adherent cells is here presented. First the complex task of assigning a specific value to all the parameters of the proposed population balance (PB) model is addressed, by also highlighting the difficulties arising when performing proper comparisons with experimental data. Then, a parametric sensitivity analysis is performed, thus identifying the more relevant parameters from a kinetics perspective. The proposed PB model can be adapted to describe cell growth under various conditions, by properly changing the value of the adjustable parameters. For this reason, model parameters able to mimic cell culture behavior under microgra... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5404653 Wed, 19 Oct 2011 04:00:00 +0100 5404653 http://www.medworm.com/index.php?rid=5396515&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24348 AbstractLignin composition in relation to its basic phenylpropanoid units, particularly the syringyl to guaiacyl (S/G) ratio, is an important property for biomass characterization and varies greatly as a function of species, genotype and environment. A rapid screening method is highly desirable to assess lignin composition in a large number of samples. We have developed a nondestructive and label‐free Fourier transform Raman (FT‐Raman) spectroscopic method that is capable of rapidly and reliably measuring the S/G ratio with minimal sample preparation. A variety of feedstocks, including hardwood (Eucalyptus globulus), softwood (Pinus radiata), herbaceous plants (Zea mays, Panicum virgatum, and Sorghum bicolor), and a model dicot (Arabidopsis thaliana) were measured using this technique ... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5396515 Wed, 19 Oct 2011 04:00:00 +0100 5396515 http://www.medworm.com/index.php?rid=5330268&cid=s_33757_61_f&fid=33757&url=http%3A%2F%2Fdx.doi.org%2F10.1002%252Fbit.24344 AbstractExperimental determination of fluxes by 13C‐tracers relies on detection of 13C‐patterns in metabolites or by‐products. In the field of 13C metabolic flux analysis, the most recent developments point towards recording labeling patterns by LC‐MS/MS directly in intermediates in central carbon metabolism to increase temporal resolution. Surprisingly, the flux studies published so far with LC‐MS measurements were based of intact metabolic intermediates ‐ thus neglected the potential benefits of using positional information to improve flux estimation. For the first time, we exploit collisional fragmentation to obtain more fine‐grained 13C‐data on intermediates of central carbon metabolism and investigate their impact in 13C metabolic flux analysis. For the case study of B... Biotechnology and Bioengineering journals http://www.medworm.com/rss/comments.php?id=5330268 Wed, 19 Oct 2011 04:00:00 +0100 5330268