bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cultivation of virus antigen in fibroblast cells using a glass fiber bed reactor
Authors: Junker B. H. , Chiou T. , Wang D. I. C. , Buckland B. C. 
Published: December 2004

AbstractThe anchorage‐dependent cell line, MRC‐5, was cultivated successfully on glass fibers with diameters ranging from 24 to 120 μm, despite vast differences in substrate curvature. Multilayer cell growth was observed, particularly for fiber diameters 30 μm and below, which differed from the typical monolayer growth observed in T‐flask cultivations. Cells were maintainable at a reduced incubation temperature and were demonstrated to support virus replication for the 21‐day antigen production period. Direct microscopic observation, along with indirect calculations, indicated that only a small fraction (about 10%) of the total available fiber surface area was occupied by cells. Thus, productivity per unit surface area was replaced by productivity per unit medium volume when evaluating fiber bed performance. Antigen and protein yields, as well as nutrient uptakes, were 1.5‐ to 2.5‐fold greater than parallel T‐flask cultures when compared on this basis. Corresponding available surface area–based values were 10‐ to 15‐fold lower for the fiber bed reactor. The multilayer cell morphology obtained in the fiber bed was attractive for antigen production when immobilized in a column reactor system. © 1993 John Wiley & Sons, Inc.
Optimal operating policy of the ultrafiltration membrane bioreactor for enzymatic hydrolysis of cellulose
Authors: Lee Seung‐Goo , Kim Hak‐Sung 
Published: December 2004

AbstractThe dilution rate of an ultrafiltration membrane bioreactor in the enzymatic hydrolysis of cellulose was optimized using the kinetic model developed by Fan and Lee.4 The sequence of optimal dilution rates was found to generally consist of an initial period of a minimal value (batch period), a subsequent period of maximum dilution rate, a period of a second batch, and a final period of a singular dilution rate. The effects of operating conditions, such as β‐glucosidase activity, operating time, maximum dilution rate, substrate feeding rate, and enzyme‐to‐substrate ratio on both the conversion yield and the sequence of optimal dilution rates were investigated. To evaluate the validity of kinetic model employed in this work, enzymatic hydrolysis was carried out using α‐cellulose as a substrate in the ultrafiltration membrane bioreactor. The experimental data were well consistent with the simulation results. © 1993 John Wiley & Sons, Inc.
Modeling lipolysis in a reversed micellar system: Part I. Conventional batch reactor
Authors: Prazeres D. M. F. , Lemos F. , Garcia F. A. P. , Cabral J. M. S. 
Published: December 2004

AbstractTriglyceride hydrolysis using Chromobacterium viscosum lipase B in a reversed micellar media was investigated in a batch‐type reactor. The dynamic evolution of the product concentration was analyzed using several mechanistic models, both from the literature and developed in this work. A kinetic model with nonlinear product inhibition was found to be the most adequate for the description of batch hydrolysis data over an extensive range of time and substrate concentration. The obtained rate equation described the time course of not only the reactions performed in this work, at different water contents (W0 = 7, 24) and pH values, but also the experimental results obtained in the literature with a Candida rugosa lipase. © 1993 John Wiley & Sons, Inc.
Peroxidase and laccase as catalysts for removal of the phenylhydrazide protecting group under mild conditions
Authors: Semenov Anatoly N. , Lomonsova Irina V. , Berezin Vasilly I. , Titov Mikhail I. 
Published: December 2004

AbstractA new method is proposed for the removal of the phenylhydrazide protecting group by the action of peroxidase or laccase, the enzymes attributed to the class of oxidoreductases. The deblocking procedure is performed under mild oxidative conditions, i.e., aqueous solution and neutral or close to neutral pH. Such mild oxidizing agents as 1 mM H2O2 and air oxygen are used for unmasking. The method is available for the deblocking of both α‐ and γ‐carboxyl groups. The enzyme‐catalyzed removal of the phenylhydrazide protecting group causes no oxidative modification nor destruction of methionine or tryptophan side chains. © 1993 John Wiley & Sons, Inc.
Membrane formation by interfacial cross‐linking of chitosan for microencapsulation of Lactococcus lactis
Authors: Groboillot A. F. , Champagne C. P. , Darling G. D. , Poncelet D. , Neufeld R. J. 
Published: December 2004

AbstractLactic acid bacteria were microencapsulated within cross‐linked chitosan membranes formed by emulsification/interfacial polymerization. The technique was modified and optimized to provide biocompatible conditions during encapsulation involving the use of mineral oils as the continuous phase and chitosan as the membrane material. Chitosan cross‐linked with hexamethylene diisocyanate or glutaraldehyde resulted in strong membranes, with a narrow size distribution about a mean diameter of 150 μm. Cell viability and activity was demonstrated by the acidification of milk. Loss of acidification activity during microencapsulation was recovered in subsequent fermentations to levels similar to that of free cell fermentations. © 1993 John Wiley & Sons, Inc.
Effects of rheological properties and mass transfer on plant cell bioreactor performance: Production of tropane alkaloids
Authors: Ballica Rabia , Ryu Dewey D. Y. 
Published: December 2004

AbstractVolumetric mass transfer coefficients, KLa were measured over an aeration rate range from 0.1 to 1.0 vvm in a 1.2‐L draft‐tube‐type airlift bioreactor for different Datura stramonium cell concentrations and correlated with superficial air velocity and rheological properties of the cell suspension. The measured KLa values (17–40 h−1) for a cell volume fraction of 0.2 (v/v) were approximately 2 times higher than those for the highest cell concentrations tested (cell volume fraction 0.7–0.8 v/v). Cell suspensions exhibited yield stress and pseudoplastic behavior. This behavior was described by the Casson model. The estimated yield stress values depended upon cell concentration with an exponent of 4.0. An empirical correlation based on the data for plant cell suspensions exhibiting yield stress was developed in order to determine aeration strategy for the plant cell cultivation in draft‐tube‐type airlift bioreactors:

Aeration rates above 1.0 vvm caused a significant drop in cell yield and product content. Maximum growth and production were obtained at 0.6 vvm aeration. The cell and product yields obtained at 1.7 vvm were 2.8 times lower than the maximum values (25 g cell DW/L and 73.8 mg tropane alkaloid/L). The effects of the increased aeration rates on cell yield were also evaluated in terms of Reynolds stress. It was found that there was a relation between cell damage and the estimated Reynolds stress. The Reynolds stress estimated for the same aeration rate decreased with increasing cell concentration, suggesting that cells in the cultures at low cell concentrations are subjected to hydrodynamic damage. In the experiments with the cell cultures having a cell concentration of 0.3 (v/v), approximately 70% reduction in cell concentration was observed when the Reynolds stress was increased from 10 to 50 dyn/cm2. © 1993 John Wiley & Sons, Inc.
On‐line monitoring of monoclonal antibodies in animal cell culture using a grating coupler
Authors: Polzius R. , Bier F. F. , Bilitewski U. , Jäger V. , Schmid R. D. 
Published: December 2004

AbstractA grating coupler was used for the on‐line determination of monoclonal antibodies produced in perfused animal cell bioreactor. The device was connected with the culture vessel via a flow‐injection analysis (FIA) system, which was controlled automatically. Specific antimouse lgG antibodies were immobilized on the surface of the sensor‐chip. After injection of the sample, the binding of mouse lgG was observed in real time. The regeneration of the binding sites of the immobilized antibodies using an acidic solution allowed the on‐line detection of produced monoclonal antibodies in the range of 10 to 150 μg/mL. In contrast to other techniques coupled to bioprocesses, the developed method represents a regenerable direct immunosensor. Results were compared with standard ELISA techniques (off‐line) and a competitive immunochemical assay using the grating coupler (off‐line). © 1993 John Wiley & Sons, Inc.
Transfer vectors for maximal expression of passenger genes in the Bombyx mori nuclear polyhedrosis virus expression system
Authors: Johnson Russell R. , Schmiel Deborah , Iatrou Kostas , Gedamu Lashitew 
Published: December 2004

AbstractA series of Bombyx mori nuclear polyhedrosis virus (Bm‐NPV) transfer vectors has been developed containing various lengths of the polyhedrin promoter, including sequences 3′ of the initiation codon. The ATG initiation codon was mutated in some of these vectors to allow for the production of authentic nonfusion proteins. The ability of the various polyhedrin promoter constructs to direct expression of foreign gene sequences was assessed using two test genes, chloramphenicol acetyl transferase (cat), and human metallothionein II. Accumulation of cat mRNA and nonfused protein was low when only polyhedrin promoter sequences to –8 (relative to the translational start site of polyhedrin mRNA) were included in the transfer vector, but cat expression was comparable with that of the wild‐type polyhedrin gene when promoter sequences to +5 were present. Further addition of polyhedrin gene sequences to +26 or +94 resulted in no further increase in expression. Similar results were obtained for expression of human metallothionein II, where constructs encoding polyhedrin–metallothionein fusion proteins containing polyhedrin sequences to at least +5 resulted in high levels of mRNA and protein accumulation. The expression vectors containing the +5, +26, or +94 BmNPV polyhedrin promoter can thus be used to direct maximal levels of production of nonfused proteins (when the polyedrin ATG has been mutated) or of fusion proteins, depending on which is more suitable for a particular application. These new vectors are a useful addition to those presently available and should increase the utility of the BmNPV expression system for large‐scale protein production. © 1993 John Wiley & Sons, Inc.
Rapid purification of DesPro(2)‐Val15‐Leu17‐aprotinin from the culture broth of a recombinant Saccharomyces cerevisiae
Authors: Barthel Thomas , Kula Maria‐Regina 
Published: December 2004

AbstractA rapid two‐step procedure has been developed for the purification of Despro(2)‐Val15‐Leu17‐aprotinin from the culture supernatant of a recombinant yeast by affinity and ion‐exchange chromatography. DesPro(2)‐Val15‐Leu17‐aprotinin was purified to homogeneity, as demonstrated by dodecylsulfate gel electrophoresis and analysis of the N‐terminal amino acid sequence. © 1993 John Wiley & Sons, Inc.
High tolerance of methanogens in granular sludge to oxygen
Authors: Kato Mario T. , Field Jim A. , Lettinga Gatze 
Published: December 2004

AbstractThis research assessed the effect of oxygen exposure on the methanogenic activity of anaerobic granular sludges. The toxicity of oxygen to acetoclastic methanogens in five different anaerobic granular sludges was determined in serum flasks with effective gas‐to‐liquid volumes of 4.65 to 1. The amount of oxygen that caused 50% inhibition of the methanogenic activity after 3 days of exposure ranged from 7% to 41% oxygen in the head space. These results indicate that methanogens located in granular sludge have a high tolerance for oxygen. The most important factor contributing to the tolerance was the oxygen consumption by facultative bacteria metabolizing biodegradable substrates. Uptake of oxygen by these bacteria creates anaerobic microenvironments where the methanogenic bacteria are protected. The results also indicate that methanogens in sludge consortia still have some tolerance to oxygen, even in the absence of facultative substrate for oxygen respiration. © 1993 John Wiley & Sons, Inc.
Modeling the regulation of bacterial genes producing proteins that strongly influence growth
Authors: Axe Douglas D. , Bailey James E. 
Published: December 2004

AbstractA theoretical method for comparing the performance of rival models of bacterial genetic regulation is presented. The particukar difficulties involved in describing the regulated synthesis of proteins that strongly influence cell growth are identiied, and the method is specifically designed to treat such cases. The method employs a mathematical description of intrinsic perturbations occurring during exponential growth to test the performance of regulatory models. Specific models of transcriptional and translational regulation are inserted into a general gene‐expression framework in order to determine their control responses. Applying thhis approach to examine the regulation of RNA polymerase synthesis in Eschericia coli provides support for the hypothesis that rpoB translation is regulated by cooperative binding of multiple RNA polymerase molecules to the mRNA. The framework is of a sufficiently general form that the method can be used to study mechanisms involved in controlling synthesis of any bacterial protein. © 1994 John Wiley & Sons, Inc.
Kinetic analysis of microbial sulfate reduction by desulfovibrio desulfuricans in an anaerobic upflow porous media biofilm reactor
Authors: Chen Ching‐I , Mueller Robert F. , Griebe Thomas 
Published: December 2004

AbstractAn anaerobic upflow porous media biofilm reactor was designed to study the kinetics and stoichiometry of hydrogen sulfide production by the sulfate‐reducing bacterium (SRB) Desulfovibrio desulfuricans (ATCC 5575) as the first step for the modeling and control of formation souring (H2S) in oil field porous media. The reactor was a packed bed (50 × 5.5 cm) tubular reactor. Sea sand (140 to 375 μm) was used as the porous media. The initial indication of souring was the appearance of well‐separated black spots (precipitates of iron sulfide) in the sand bed. The blackened zones expanded radially and upward through the column. New spots also appeared and expanded into the cone shapes. Lactate (substrate) was depleted and hydrogen sulfide appeared in the effluent.Analysis of the pseudo–steady state column shows that there were concentration gradients for lactate and hydrogen sulfide along the column. The results indicate that most of the lactate was consumed at the front part of the column. Measurements of SRB biomass on the solid phase (sand) and in the liquid phase indicate that the maximum concentration of SRB biomass resided at the front part of the column while the maximum in the liquid phase occurred further downstream. The stoichiometry regarding lactate consumption and hydrogen sulfide production observed in the porous media reactor was different from that in a chemostat. After analyzing the radial dispersion coefficient for the SRB in porous media and kinetics of microbial growth, it was deduced that transport phenomena dominate the souring process in our porous media reactor system. © 1994 John Wiley & Sons, Inc.
Novel protein a affinity matrix prepared from two‐dimensional protein crystals
Authors: Weiner Christian , Sára Margit , Sleytr Uwe B. 
Published: December 2004

AbstractIn this article, we describe a novel type of affinity matrix which was prepared by covalently binding Protein A to crystalline cell surface layers (S‐layers) from the gram‐positive Clostridium thermohydrosulfuricum L111‐69. S‐layers were used in the form of cell wall fragments, which were obtained by breaking whole cells by ultrasonification and removing the cell content and the plasma membrane. In these thimble shaped structures, revealing a size of 1 to 2 μm, the peptidoglycan‐containing layer was covered on both faces with a hexagonally ordered S‐layer lattice composed of identical glycoprotein subunits. After crosslinking the S‐layer protein with glutaraldehyde, carboxyl groups from acidic amino acids were activated with carbodiimide and used for immobilization of Protein A. Quantitative determination confirmed that up to two Protein A molecules were bound per S‐layer subunit leading to a dense monomolecular coverage of the immobilization matrix with the ligand.Affinity microparticles were capable of adsorbing lgG from solutions of purified preparations, from artificial lgG‐albumin mixtures, and from serum. The amount of lgG bound to affinity microparticles corresponded to the theoretical saturation capacity. Under appropriate conditions, up to 95% of the adsorbed lgG could be eluted again. Affinity microparticles were found to have an extremely low Protein A leakage and a high stability toward mechanical forces. Because pores in the S‐layer lattice revealed a size of 4 to 5 nm, immobilization of Protein A and adsorption of lgG was restricted to the outermost surface area. This excludes mass transfer problems usually encountered with affinity matrices prepared from amorphous polymers where more than 90% of the ligands are immobilized in the interior. © 1994 John Wiley & Sons, Inc.
Studies of on‐line viable yeast biomass with a capacitance biomass monitor
Authors: Austin Glen D. , Watson Rodney W. J. , D'Amore Tony 
Published: December 2004

AbstractA commercially available biomass monitor has been employed in a number of applications. For capacitance monitors, a relationship between capacitance measurement and cell counts or colony forming units has been reported in the literature. However, for use as an online instrument, a more practical correlation with the biomass concentration is needed. In this study, we followed the batch growth of brewer's yeast and a correlation with viable biomass concentration (g DW/L) was demonstrated. This correlation was utilized with the capacitance biomass monitor in a control loop to maintain setpoint biomass levels in a cyclic reactor under perturbations. Not only did the system demonstrate the capability of the biomass monitor to control biomass in such a system, but it also confirmed the correlation reported in our earlier work. © 1994 John Wiley & Sons, Inc.
Partition coefficients of substrates and products and solvent selection for biocatalysis under nearly anhydrous conditions
Authors: Yang Zhen , Robb Donald A. 
Published: December 2004

AbstractThe effect of solvent on the activity of mushroom tyrosinase toward three substrates was studied at a constant water activity of either 0.74 or 0.86. No simple correlation was observed between enzyme activity and log P, but partition coefficients of substrate (Ps) and product (Pp) gave systematic relations with enzyme activity. When initial reaction rates were considered, there was a bellshaped relationship between enzyme activity and Ps with an optimal Ps for each substrate. This can be explained by assuming that the solvent affected the enzyme activity primarily by affecting the substrate concentration in the aqueous layer around the catalyst where the enzymic reaction occurs. When long‐term reaction rates were considered, a high Pp/Ps ratio was consistent with preservation of enzyme activity. © 1994 John Wiley & Sons, Inc.
Feeding heterogeneity in ciliate populations: Effects of culture age and nutritional state
Authors: Hatzis Christos , Srienc Friedrich , Fredrickson A. G. 
Published: December 2004

AbstractWe have used a novel approach in conjunction with flow cytometry to quantify the biological heterogeneity of populations of the ciliate Tetrahymena pyriformis. It was found that the rate of particle uptake of exponentially growing cells is not uniform among cells and partially correlated with cell size. The physiological state and growth history of the culture was found to affect to a large degree the population's feeding heterogeneity. Stationary phase populations exhibited more uniform feeding behavior, as cell aging affects all cells and effectively reduces their ability to feed. Cells that were removed from the growth medium and resuspended in nonnutritive medium exhibited a more heterogeneous feeding behavior. The starved cells were stimulated to feed at considerably higher rates, and the stimulatory effect was more pronounced for larger cells. It is therefore demonstrated that population heterogeneity has to be evaluated in conjunction with the populations growth state as it is determined by the history of the population's growth and nutritional state. © 1994 John Wiley & Sons, Inc.
Cellulose morphology and enzymatic reactivity: A modified solute exclusion technique
Authors: Gama F. M. , Teixeira J. A. , Mota M. 
Published: December 2004

AbstractAn expeditious and accurate simplification of Stone and Scallan's solute exclusion technique was developed, thereby avoiding several sources of experimental error coupled with the determination of cellulose pore volume. Using this method, it is shown that cellulolytic enzymes do not enter into the micropores of five studied celluloses. These results suggestes that hydrolysis occurs initially at the external surface of the fibers. This surface area was calculated with the help of adsorption isotherms of bovine serum albumin. The obtained values for the different samples agree with the microscopically observed cellulose morphology. The correlation obtained by several authors relating cellulose porosity and its digestibility is explained as a consequence of the lower crystallinity and easier fragmentation of the more porous celluloses during hydrolysis. © 1994 John Wiley & Sons, Inc.
Ribosomal protein limitations in Escherichia coli under conditions of high translational activity
Authors: Laffend L. , Shuler M. L. 
Published: December 2004

AbstractDetails of the mechanism for ribosome synthesis have been incorporated in the single‐cell Escherichia coli model, which enable us to predict the amount of protein synthesizing machinery under different environmental conditions. The predictions agree quite well with available experimental data. The model predicts that ribosomal protein limitations are important when the translational apparatus is in high demand. Ribosomal RNA synthesis is induced by an increase in translational activity, which, in turn, stimulates ribosomal protein synthesis. However, as the demand increases still more, the ribosomal protein mRNA must compete with the plasmid mRNA for ribosomes, and the efficiency of translation of ribosomal proteins is reduced. © 1994 John Wiley & Sons, Inc.