bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fed‐batch cultivation of animal cells using different medium design concepts and feeding strategies
Authors: Xie Liangzhi , Wang Daniel I. C. 
Published: December 2004

AbstractIn animal cell cultivation, cell density and product concentration are often low due to the accumulation of toxic end‐products such as ammonia and lactate and/or the depletion of essential nutrients. A hybridoma cell line (CRL‐1606) was cultivated in T‐flasks using a newly devised medium feeding strategy. The goals were to decrease ammonia and lactate formation by the design of an initial medium which would provide a starting environment to achieve optimal cell growth. This was followed by using a stoichiometric equation governing animal cell growth and then designing a supplemental medium for feeding strategy used to control the nutritional environment. The relationship between the stoichiometric demands for glutamine and nonessential amino acids was also studied. Through stoichiometric feeding, nutrient concentrations were controlled reasonably well. Consequently, the specific production rate of lactate was decreased by fourfold compared with conventional fed‐batch culture and by 26‐fold compared with conventional batch culture. The specific production rate of ammonia was decreased by tenfold compared with conventional fed‐batch culture and by 50‐fold compared with conventional batch culture. Most importantly, total cell density and monoclonal antibody concentration were increased by five‐ and tenfold respectively, compared with conventional batch culture. © 1994 John Wiley & Sons, Inc.
Redox conditions for stimulation of in vitro folding and assembly of the glycoprotein hormone chorionic gonadotropin
Authors: Huth Jeffrey R. , Weijun Feng , Ruddon Raymond W. 
Published: December 2004

AbstractThe formation of native disulfide bonds during in vitro protein folding can be limiting in obtaining biologically active proteins. Thus, optimization of redox conditions can be critical in maximizing the yield of renatured, recombinant proteins. We have employed a folding model, that of the β subunit of human chorionic gonadotropin (hCG‐ β), to investigate in vitro oxidation conditions that facilitate the folding of this protein, and have compared the in vitro rates obtained with the rate of folding that has been observed in intact cells. Two steps in the folding pathway of hCG‐β were investigated: the rate‐limiting events in the folding of this protein, and the assembly of hCG‐β with, hCG‐α. The rates of these folding events were determined with and without protein disulfide isomerase (PDI) using two different types of redox reagents: cysteamine and its oxidized equivalent, cystamine, and reduced and oxidized glutathione. Rates of the rate‐limiting folding events were twofold faster in cysteamine/cystamine redox buffers than in glutathione buffers in the absence of PDI. Optimal conditions for hCG‐β folding were attained in a 2 mM glutathione buffer, pH 7.4, that contained 1 mg/mL PDI and in 10μM cysteamine/cystamine, pH 8.7, without PDI. Under these conditions, the half‐time of the ratelimiting folding event was 16 to 20 min and approached the rate observed in intact cells (4 to 5 min). Moreover, folding of the β subunit under these conditions yields a functional protein, based on its ability to assemble with the α subunit. The rates of assembly of hCG‐β with hCG‐α in the cysteamine/cystamine or glutathione/PDI redox buffers were comparable (t1/2/sb> = 9 to 12 min). These studies show that rates of folding and assembly events that involve disulfide bond formation can be optimized by a simple buffer system composed of cysteamine and cystamine. © 1994 John Wiley & Sons, Inc.
Equilibrium and kinetic studies on reversible and irreversible denaturation of micrococcal nuclease
Authors: Nohara Daisuke , Yamada Toshiyasu , Watanabe Akiko , Sakai Tomoya 
Published: December 2004

AbstractThe effect of pH and temperature on the thermal denaturation of micrococcal nuclease wer4e investigated. The ranges employed were between pH3.30 and pH9.70 and between 10°C and 85°C, respectively. The reversible denaturation involved in the whole process was clearly discriminated from the irreversible one. The former took place with a large enthalpy change of 384 kJ mol−1 at pH 9.70, where the enzyme exhibited it s maximum activity. The latter probably led to aggregation because the successive long incubation after complete deactivation caused precipitation. A reasonable scheme explaining the process involving both denaturations was proposed and the kinetic on the irreversible deactivation was performed. It was revealed that the irreversible deactivation involved two types of reactions whose activation energies were relatively small: 22.2 kJ mol−1 and 18.8kJ mol−1. The presence of sucrose suppressed the reversible denaturation without significant influence on enthalpy change, whereas it affected little the irreversible deactivation kinetically. The effects of pH change and addition of sucrose on the denaturation were discussed thermodynamically, especially in terms of the entropy change. © 1994 John Wiley & Sons, Inc.
Cell cycle kinetics and monoclonal antibody productivity of hybridoma cells during perfusion culture
Authors: Park Sun Ho , Ryu Dewey D. Y. 
Published: December 2004

AbstractThe flow‐cytometric (FCM) analysis of bivariate DNA/lgG distributions has been conducted to study the cell cycle kinetics and monoclonal antibody (MAb) production during perfusion culture of hybridoma cells. Three different perfusion rates were employed to demonstrate the dependency of MAb synthesis and secretion on cell cycle and growth rate. The results showed that, during the rapid growth period of perfusion culture, the level of intracellular igG contents of hybridoma cells changed significantly at each perfusion rate, while the DNA histograms showing cell cycle phases were almost constant. Meanwhile, during the reduced growth period of perfusion culture, the fraction of cells in the S phase decreased, and the fraction cells in the G1/G0 phase increased with decreasing growth rate. The fraction of cells in the G2/M phase was relatively constant during the whole period of perfusion culture. Positive correlation was found between mean intracellular IgG contents and the specific MAb production rate, suggesting that the deletion of intracellular IgG contents by a flow cytometer could be used as a good indicator for the prediction of changes in specific MAb productivity following manipulation of the culture condition. © 1994 John Wiley & Sons, Inc.
Morphological kinetics and distribution in somatic embryo cultures
Authors: Chi Chung‐Ming , Vits Hugo , Staba E. John , Cooke Todd J. , Hu Wei‐Shou 
Published: December 2004

AbstractThe environmental effects on developing somatic embryos should be characterized not only by the growth based on biomass, but also by the morphological properties and size. We have previously developed a discrete classifier to separate developing embryos into distinct morphological classes. In this study, a continuous descriptor using the distributions of magnitude of features representing morphological characteristics and size information was used to describe the developing embryo populations. The identity of the population was examined by comparing either the distributions of all features or key features. The method was applied to characterize the kinetics of carrot embryo populations cultivated in the presence and absence of triiodobenzoic acid(TIBA), an inhibitor of auxin polar transport. Optimal sample size for morphological characterization was determined by the invariance of feature distributions with further increase in sample size. The overall growth and substrate consumption kinetics were only slightly affected by the presence of TIBA. However, the distribution of morphological features was significantly affected. The features showing the highest statistical significance were related to those corresponding to the roughness. The continuous descriptor for characterizing developing embryo population is potentially useful for quality control in large‐scale operations. © 1994 John Wiley & Sons, Inc.
Ethene removal from a synthetic waste gas using a dry biobed
Authors: De Heyder Bart , Overmeire Ann , Van Langenhove Herman , Verstraete Willy 
Published: December 2004

AbstractA packed granular activated carbon (GAC) biobed, inoculated with the ethane‐degrading strain Mycobacterium E3, was used to study ethene removal from a synthetic waste gas. Ethene, for which the dimensionless partition coefficient for an air‐water system at 20°C is about 7.6, was used as a model compound for poorly water soluble gaseous pollutants. In a first mode or operation, the GAC biobed was sprinkled intermittently and the waste gas influent was continuously pre‐humidified, establishing relatively moist conditions (water content >40% to 45%). A volumetric ethene removal rate of 0.382 kg COD · m−3 · d−1 (0.112 kg ethene · m−3 · d−1) was obtained for an influent concentration of 125 ppm, a superficial waste gas velocity of 3.6E−3 m · s−1 and a pseudo residence time of 45 s. However, in the second mode of operation, omitting the pre‐humidification of the waste gas influent and establishing a “dry” biobed (water content <40% to 45%), and thus obtaining better mass transfer to the biofilm, the ethene removal could be doubled for otherwise comparable operating parameters. Furthermore, under decreased wetting and for the given experimental conditions (influent concentration 125 to 816 ppm, waste gas superficial velocity 3.0E−3 m ·s−1, pseudo waste gas residence time 43 s), the ethene removal was not limited by mass transfer of ethene through the water layer covering the biofilm. © 1994 John Wiley & Sons, Inc.
Protein complexation with acrylic polyampholytes
Authors: Patrickios Costas S. , Hertler Walter R. , Hatton T. Alan 
Published: December 2004

AbstractThe interaction of dilute mixtures of proteins and ABC triblock methacrylic polyampholytes at different values of pH was investigated turbidimetrically. The onset of interaction was manifested by large changes in turbidity at certain critical pHs which lie close to the isoelectric points of the two interacting components. Protein precipitation yields in protein‐polyampholyte binary mixtures followed the corresponding turbidity profiles and varied from 10% to 90%. The synthetic polyampholytes self‐aggregate around their isoelectric point. The kinetics of precipitation of one of the same polymer with soybean trypsin inhibitor were studied, with turbidity‐based characteristic times (exponential fit) of 2–3 min. The kinetics of precipitation of the protein‐polymer mixture are slower than that of pure polymer because a small, but steady, long‐term increase in turbidity is observed in the former case. The pH‐dependence of the turbidity of binary mixtures of one protein and one synthetic polyampholyte, as well as a tertiary mixture of two proteins and one polyampholyte, were measured 30 min after the pH adjustment. The observations in these experiments along with the measured protein precipitation yields in the binary mixtures and the polyampholyte self‐aggregation can be used for polymer removal and recycling. The latter constitutes a significant advantage over the use of homopolyelectrolytes which cannot easily be recycled. © 1994 John Wiley & Sons, Inc.
Immobilization of “Disguised” yeast in chemically crosslinked chitosan beads
Authors: Freeman Amihay , Dror Yael 
Published: December 2004

AbstractA new simple method for the preparation of chemically crosslinked chitosan beads is presented. It consists of the dropwise addition of 2–3% (w/v) low molecular weight chitosan solution containing 2% (w/v) glyoxal in 1% (w/v) tetrasodiumdiphosphate, pH 8.0. Immobilized viable baker's yeast (Saccharomyces cerevisiae) could be obtained via gel entrapment within the new beads when means preventing their direct contact with soluble chitosan were provided, “disguising” the cells until gelation and crosslinking were completed. Such means included cell suspension in castor oil or mixing with carboxymethyl‐cellulose powder. Application of these means was shown to be necessary, as cells exposed to soluble chitosan immediately lost their viability and glycolytic activity. Yeast disguised in castor oil was also protected from bead reinforcement by glutaraldehyde treatment, significantly strengthening bead stability while operating under acidic conditions. This capability was demonstrated by continuous ethanol production by chitosan entrapped yeast. © 1994 John Wiley & Sons, Inc.
A dense cell retention culture system using stirred ceramic membrane reactor
Authors: Suzuki Takahiro , Sato Takeshi , Kominami Minoru 
Published: December 2004

AbstractA novel reactor design incorporating porous ceramic tubes into a stirred jar fermentor was developed. The stirred ceramic membrane reactor has two ceramic tubular membrane units inside the vessel and maintains high filtration flux by alternating use for filtering and recovering from clogging. Each filter unit was linked for both extraction of culture broth and gas sparging. High permeability was maintained for long periods by applying the periodical control between filtering and air sparging during the stirred retention culture of Saccharomyces cerevisiae. The ceramic filter aeration system increased the kLa to about five times that of ordinary gas sparing. Using the automatic feeding and filtering system, cell mass concentration reached 207 g/L in a short time, while it was 64 g/L in a fed‐batch culture. More than 99% of the growing cells were retained in the fermentor by the filtering culture. Both yield and productivity of cells were also increased by controlling the feeding of fresh medium and filtering the supernatant of the dense cells culture. © 1994 John Wiley & Sons, Inc.
Hydrogen production from organic substrates in an aerobic nitrogen‐fixing marine unicellular cyanobacterium Synechococcus sp. strain Miami BG 043511
Authors: Luo Yao‐Hua , Mitsui Akira 
Published: December 2004

AbstractSynechococus sp. strain Miami BG 043511 exhibits very high H2 photoproduction from water, but the H2 photoproduction capability is lost rapidly with the age of the batch culture. The decreases of the capability coincides with the decrease of cellular glucose (glycogen) content. However, H2 photoproduction capability can be restored by the addition of organic substrates. Among 40 organic compounds tested, carbohydrates such as glucose, fructose, maltose, and sucrose were effective electron donors. Among organic acids tested, only pyruvate was an effective electron donor. Among alcohols tested, glycerol was a good electron donor. These results demonstrate that this unicellular cyanobacterium exhibits a wide substrate specificity for H2 photoproduction but has a different substrate specificity compared to photosynthetic bacteria. The maximum rates of H2 photoproduction from a 6‐day‐old batch culture with 25 mmol of pyruvate, glucose, maltose, sucrose, fructose, and glycerol were 1.11, 0.62, 0.50, 0.47, 0.30, and 0.39 µmoles per mg cell dry weight per hour respectively. Therefore, this cyanobacterium strain may have a potential significance in removing organic materials from the wastewater and simultaneously transforming them to H2 gas, a pollution free energy. The activity of nitrogenase, which catalyzes hydrogen production, completely disappeared when intracellular glucose (glycogen) was used up, but it could be restored by the addition of organic substrates such as glucose and pyruvate. © 1994 John Wiley & Sons, Inc.
Catalytic behavior of Pseudomonas cepacia lipase in w/o microemulsions
Authors: Stamatis H. , Xenakis A. , Dimitriadis E. , Kolisis F. N. 
Published: December 2004

AbstractThe activity of purified Pseudomonas cepacia lipase has been investigated in esterification reactions of various aliphatic alcohols with natural fatty acids. The reactions were carried out in microemulsions formed in isooctane by bis‐(2‐ethylhexyl)sulfosuccinate sodium salt (AOT). Kinetic studies showed that the reaction follows a ping‐pong bi–bi mechanism with inhibition by both substrates. The apparent kinetic parameters of the reaction were found to be Km octanol = 310 mM, Km lauric acid = 78 mM, and Vmax = 250 μmol min−1 mg−1. The same system was used for the synthesis of mono‐ and diglycerides from glycerol and lauric acid, which was successful at very low wo values. The catalytic behavior of P. cepacia lipase was also studied in esterification reactions performed in a nonionic microemulsion system formulated by tetraethyleneglycoldodecylether (C12E4). The optimum activity was found at about wo = 8. The apparent values of Vmax app and Km app for octanol were calculated and found to be 100 μmol min−1 mg−1 and 76 mM, respectively. © 1995 John Wiley & Sons, Inc.
Influence of cell‐ and media‐derived factors on the integrity of a human monoclonal antibody after secretion into serum‐free cell culture supernatants
Authors: Ackermann Marcus , Jäger Volker , Marx Uwe 
Published: December 2004

AbstractTo investigate the effects of factors secreted by different cell lines on human monoclonal antibody (MAb) integrity, 600 mg of a human MAb, which specifically binds to human erythrocytes, were produced in a perfusion process. After purification by protein A affinity chromatography, the MAb was used for integrity testing in supernatants of several cell lines to investigate their potential to degrade the antibody in the extracellular environment. One insect cell line (IPLB‐SF‐21 AE) and four mammalian cell lines [CHO K1, BHK‐21 (C13), C1271, P3‐X63‐Ag8.653], all of them commonly used for the production of recombinant proteins, and the human–human–mouse heterohybridoma cell line itself (H‐CB‐hahE), were adapted to serum‐free culture media. For integrity testing all cell lines were cultivated in spinner flasks using serum‐free media supplemented with 30 μg mL−1 of purified MAb. MAb integrity was assayed by SDS polyacrylamide gel electrophoresis (SDS‐PAGE), isoelectric focusing, both followed by Western blotting, and an antigen binding assay. None of the mammalian cells showed any detectable effects on antibody stability and integrity during exponential growth, whereas isoelectric focusing of monoclonal antibody taken from IPLB‐SF‐21 AE culture supernatants revealed a new band indicating a partial modification of the MAb by secreted factors of these cells. This observation did not correlate with the total proteolytic activity, which was measured in all supernatants and found to be lowest in the insest cell cultures. For mammalian cell cultures, it could be concluded from these findings that shifts of the antibody microheterogeneity pattern, which can be found normally as a result of variations in different production parameters, are not caused by extracellular factors once the product has been secreted into the supernatant. In addition to their well‐known advantages in posttranslational modifications (e.g., formation of complex type N‐glycans), mammalian cells appear to be more suitable as expression systems for human monoclonal antibodies to be used in vivo when compared with baculovirus‐infected insect cells. © 1995 John Wiley & Sons, Inc.
Cultivation of hybridoma cells in an inclined bioreactor
Authors: Lu George Z. , Gray Murray R. , Thompson B. G. , Suresh M. R. 
Published: December 2004

AbstractMurine hybridoma cells were grown in a bubble column that was inclined up to 45° from vertical. Inclining the column by a few degrees separated the rising bubbles against the upper surface, leaving the bulk of the liquid bubble free. The liquid was circulated well by the rising bubbles, but collection of cells by rising bubbles and exposure of cells to bursting bubbles were minimized. Maximum viable cell count and exponential growth of the cells were not affected by inclination, but an inclination of 30° gave an antibody titer of 42 mg/L, which more than doubled the yield of 17 mg/L in the vertical position. By comparison, the culture gave yields of 30 mg/L when grown in spinner flasks. The enhanced antibody production in the inclined bioreactor corresponded to a prolonged stationary phase of 45 h. © 1995 John Wiley & Sons, Inc.
Diffusion of Cu2+ in calcium alginate gel beads: Further analyses
Authors: Chaiken Robert F. 
Published: December 2004

AbstractThe diffusivity of Cu2+, as determined by previous authors from analysis of experimental data in terms of the shrinking core (SCM) and linear absorption (LAM) models, is examined in light of the ability of the models to curve fit all the data. It is concluded from this further analysis that previous conclusions depicting the LAM to have an advantage over the SCM for predictive value are not justified. It is also shown that equally good curve fits can be obtained with a recent absorption/desorption model of diffusion which considers directly, through distribution theory, the effect of heterogeneity of material properties on the rate of diffusion. © 1995 John Wiley & Sons, Inc.
A modeling study of anaerobic biofilm systems: II. Reactor modeling
Authors: Flora Joseph R. V. , Suidan Makram T. , Biswas Pratim , Sayles Gregory D. 
Published: December 2004

AbstractA rigorous steady‐state model of anaerobic biofilm reactors taking into account acid–base and gas–phase equilibria in the reactor in conjunction with detailed chemical equilibria and mass transfer in acetate‐utilizing methanogenic biofilms is presented. The performances of ideal completely stirred tank reactors (CSTRs) and plug‐flow reactors, as well as reactors with nonideal hydraulic conditions, are simulated. Decreasing the surface loading rate increases the acetate removal efficiency, while decreasing the influent pH and increasing the buffering capacity improves the removal efficiency only if the bulk pH of the reactor shifts toward more optimal values between 6.8 to 7.0. The reactor can have negative or positive removal efficiencies depending on the start‐up conditions. The respiration coefficient plays a critical role in determining the minimum influent pH required for reactor recovery after failure. Having multiple CSTRs‐in‐series generally increases the overall removal efficiency for the influent conditions investigated. Monitoring of the influent feed quality is critical for plug‐flow reactors, becasue failure of the initial sections of the reactor may cause a cascading effect that may lead to a rapid reactor failure. © 1995 John Wiley & Sons, Inc.
Development of a predictive description of an immobilized‐cell, three‐phase, fluidized‐bed bioreactor
Authors: Petersen James N. , Davison Brian H. 
Published: December 2004

AbstractA fully predictive mathematical description of a three‐phase, tapered, fluidized‐bed bioreactor is developed. This mathematical model includes the effects of the tapered bed, variable dispersion coefficient, and variable solid holdup upon the concentration profiles developed in the bed. In addition, the effect of the concentration profile which is developed inside the biocatalyst bead is included by means of an effectiveness factor calculation. Using accepted correlations for the dispersion coefficient and for the liquid, gas, and solid holdup in the bed, the model is fully predictive. The model was found to adequately predict experimental obtained concentration profiles. Then, the model was used to examine the various phase holdups through the bed and the degree to which the dispersion coefficient varied through the bed. The effect of changes in these calculated variables upon the reaction rate is discussed. © 1995 John Wiley & Sons, Inc.