bluuebunny/crossref_metadata_2025_split huggingface dataset:
High‐density continuous cultures of hybridoma cells in a depth filter perfusion system
Authors: Oh Duk Jae , Choi Sang Kyo , Chang Ho Nam 
Published: December 2004

AbstractA depth filter perfusion system (DFPS) for animal cell culture was developed and its use in continuous highdensity cultures of hybridoma cells was investigated. In the DFPS, based on cell immobilization in a cylindrical depth filter matrix, cells were easily immobilized and cultivated by simple medium recirculation. The cell density in the 20‐μm pore size filter matrix reached up to 3 × 107 cells/mLin less than 10 days. This resulted in a high monoclonal antibody productivity of 744 mg/L/day, which was 25‐35 times higher than that of continuous‐suspension cultures using the same cell line. The 20‐μm pore filter retained more cells than the 30‐μm filterin a shorter period. The DFPS provides advantages of low‐cost set‐up, easy operation, and scale‐up in the cultures of anchorage‐independent cells. It also has a high potential for anchorage‐dependent cell cultures because of its unusually high surface‐to‐volume ratio of 450‐600 cm2/cm3. © 1994 John Wiley & Sons, Inc.
Effects of intermolecular thiol–disulfide interchange reactions on bsa fouling during microfiltration
Authors: Kelly Sean T. , Zydney Andrew L. 
Published: December 2004

AbstractSeveral studies have shown that one of the critical factors governing protein fouling of microfiltration membranes is the presence of denaturedand/or aggregated protein in the bulk solutions. Experiments were performed to evaluate the role of intermolecular disulfide interchange reactionson protein aggregation and membrane fouling during stirred cell microfiltration of bovine serum albumin (BSA). The flux decline during BSA filtration was quite dramatic due to the formation of a protein deposit thatfully covered the membrane pores. This flux decline could be completely eliminated by capping the free sulfhydryl group present on the BSA with eithera carboxymethyl or cysteinyl group, demonstrating the critical importance of this free thiol in the intermolecular aggregation reactions and, in turn, protein fouling. BSA aggregation during storage could be reduced by the addition of metal chelators (EDTA and citrate) or dithiothreitol, orby storage at lower pH (7.0) these solutions all had a significantly lower rate of fouling upon subsequent filtration. This behavior is completely consistent with the known chemistry of the thiol–disulfide interchange reaction, demonstrating that an understanding of these intermolecular (aggregation) reactions can provide a rational framework for the analysis and control of protein fouling in these membrane systems. © 1994 John Wiley & Sons, Inc.
Improvement of cloned α‐amylase gene expression in fed‐batch culture of recombinant Saccharomyces cerevisiae by regulating both glucose and ethanol concentrations using a fuzzy controller
Authors: Shiba Sumihisa , Nishida Yoshio , Park Yong Soo , Lijima Shinji , Kobayashi Takeshi 
Published: December 2004

AbstractThe effect of ethanol concentration on cloned gene expression in recombinant Saccharomyces cerevisiae strain 20B‐12 containing one of two plasmids, pNA3 and pNA7, was investigated in batch cultures. Plasmids pNA3 and pNA7 contain the α‐amylase gene under the control of the SUC2 or PGK promoter, respectively. When the ethanol concentration was controlled at 2 to 5 g/L, the gene expressions were two times higher than those at 20 g/L ethanol. The increase the gene expression by maintaining both the ethanol and glucose concentrations at low levels, a fuzzy ontroller was developed. The concentrations of glucose and ethanol were controlled simultaneously at 0.15 and 2 g/L, respectively, in the production phase using the fuzzy controller in fed‐batch culture. The synthesis of α‐amylase was induced by the low glucose concentration and maintained at a high level of activity by regulating the ethanol concentration at 2 g/L. The secretory α‐amylase was induced by the low glucose concentration and maintained at a high level of activity by regulating the ethanol concentration at 2 g/L. The secretory α‐amylase activities of cells harboring plasmids pNA3 and pNA7 in fed‐batch culture were 175 and 395 U/mL, and their maximal specific activities 7.7 and 12.4 U/mg dry cells, respectively. These values are two to three times higher in activity and three to four times higher in specific activity than those obtained when glucose only was controlled. © 1994 John Wiley & Sons, Inc.
Adsorption and synergism of cellobiohydrolase I and II of Trichoderma reesei during hydrolysis of microcrystalline cellulose
Authors: Medve József , Ståhlberg Jerry , Tjerneld Folke 
Published: December 2004

AbstractHydrolysis of microcrystalline cellulose (Avicel) by cellobiohydrolase I and II (CBH I and II) from Trichoderma reesei has been studied. Adsorption and synergism of the enzymes were investigated. Experiments were performed at different temperatures and enzyme/substrate ratios using CBH I and CBH II alone and in reconstituted equimolar mixtures. Fast protein liquid chromatography (FPLC) analysis was found to be an accurate and reproducible method to follow the enzyme adsorption. A linear correlation was found between the conversion and the amount of adsorbed enzyme when Avicel was hydrolyzed by increasing amounts of CBH I and/or CBH II. CBH I had lower specific activity compared to CBH II although, over a wide concentration range, more CBH I was adsorbed than CBH II. Synergism between the cellobiohy‐drolases during hydrolysis of the amorphous fraction of Avicel showed a maximum as a function of total enzyme concentration. Synergism measured as a function of bound enzyme showed a continuous increase, which indicates that by decreasing the distance between the two enzymes the synergism is enhanced. The adsorption process for both enzymes was slow. Depending on the enzyme/substrate ratio it took 30–90 min to reach 95% of the equilibrium binding. The amount of bound enzyme decreased with increasing temperature. The two enzymes compete for the adsorption sites but also bind to specific sites. Stronger competition for adsorption sites was shown by CBH I. © 1994 John Wiley & Sons, Inc.
Flow parameters associated with hydrodynamic cell injury
Authors: Garcia‐Briones Migual A. , Chalmers Jeffrey J. 
Published: December 2004

AbstractTwo flow parameters are proposed for the analysis of flows that have potential to damage animal cells. They are the state of stress (characterized by the second invariant of the stress tensor) and the flow classification parameter RD (which is related to the possibility of stress relaxation). We consider the flow that occurs when a 1.7‐mm bubble collapses at a liquid interface. Using these two parameters, we show the regions in which the flow is strong in terms of high hydrodynamic stresses and elongation characteristics. © 1994 John Wiley & Sons, Inc.
A fluid dynamic study of the retrofitting of large agitated bioreactors: Turbulent flow
Authors: Nienow A. W. , Hunt G. , Buckland B. C. 
Published: December 2004

AbstractStudies were conducted in three 19‐m3 fermentors (14 m3 working volume, aspect ratio = 3:1), one fitted with four Rushton turbines (D/T = 0.35), one with three Lightnin' A315 hydrofoil impellers (D/T = 0.46). The power drawn under the same aerated conditions relative to the unaerated ones was always greater with the hydrofoils, which gives them the potential for enhanced mass transfer rates under practical operating conditions. However, the power draw was also sensitive to the magnitude of the unaerated power. Indeed, at low unaerated specific power (∼0.6 W‐kg) and high air flow rates (∼1vvm), the relative power draw with the hydrofoils could be even greater than 1. The hold‐up with each of the impellers was broadly similar at the same aeration rate and power input, though the later had a much smaller impact in these large vessels than has been reported in the literature based on smaller scale work. As usual, repressed coalescence caused increased hold‐up, and, with the hydrofoils, this increase was associated with a lower power draw. Because of the greater mechanical vibration of the reactors with the hydrofoils, vibration characteristics of the vessels were measured and they were very similar. The results showed that provided care is taken in the mechanical design of the system, such impellers can operate reliably in large‐scale fermentations with the potential for enhanced biological performance. © 1994 John Wiley & Sons, Inc.
Rapid screening for metabolite overproduction in fermentor broths, using pyrolysis mass spectrometry with multivariate calibration and artificial neural networks
Authors: Goodacre Royston , Trew Sally , Wrigley‐Jones Carys , Neal Mark J. , Maddock John , Ottley Thomas W. , Porter Neil , Kell Douglas B. 
Published: December 2004

AbstractBinary mixtures of model systems consisting of the antibiotic ampicillin with either Escherichia coli or Staphylococcus auresu were subjected to pyrolysis mass spectrometry (PyMS). To deconvolute the pyrolysis mass spectra, so as to obtain quantitative information on the concentration of ampicilin in the mixtures, partial least squares regression (PLS), principal components regression (PCR), and fully interconnected feedforward artificial neural networks (ANNs) were studied. In the latter case, the weights were modified using the standard backpropagation algorithm, and the nodes used a sigmoidal squsahing funciton. It was found that each of the methods could be used to provide calibration models which gave excellent predictions for the concentrations of ampicillin in samples on which they had not been trained. Furthermore, ANNs trained to predict the amount of ampicilin in E. coli were able to generalise so as to predict the concentration of ampicillin in a S. aureus background, illustrating the robustness of ANNs to rather substantial variations in the biological background. The PyMS of the complex mixture of ampicilin in bacteria could not be expressed simply in terms of additive combinations of the spectra describing the pure components of the mixtures and their relative concentrations. Intermolecular reactions took place in the pyrolysate, leading to a lack of superposition of the spectral components and to a dependence of the normalized mass spectrum on sample size. Samples from fermentations of a single organism in a complex production medium were also analyzed quantitatively for a drug of commercial interest. The drug could also be quantified in a variety of mutant‐producing strains cultivated in the same medium. The combination of PyMS and ANNs constitutes a novel, rapid, and convenient method for exploitation in strain improvement screening programs. © 1994 John Wiley & Sons, Inc.
Diffusion of acetophenone and phenethyl alcohol in the calcium‐alginate–bakers' yeast–hexane system
Authors: Wu W. , Sidhoum M. , DeLancey G. B. 
Published: December 2004

AbstractThe intrabead diffusion coefficients of acetophenone and phenethyl alcohol were measured at 30°C in the triphasic immobilized yeast‐water‐hexane system. Saccharomyces cerevisiae cells were deactivated with hydrochloric acid and entrapped in calcium‐alginate beads. Measurements of dry cell loss during deactivation, shrinkage of the beads during deactivation and the final porosity of the beads were made for various cell loadings. Final concentrations of wet cells in the beads ranged from approximately 0.25 to 0.30 g/mL. Mass transfer in the hexane phase, external to the beads, was eliminated experimentally. The estimated error of 5% to 10% in the diffusion coefficients is within the experimental error associated with the bead method. The effect of significant sampling volumes on the diffusivities was estimated theoretically and accounted for experimentally. The intrabead concentration of acetophenone and phenethyl alcohol was 150 to 800 ppm. The deactivated cells were shown to be impervious to acetophenone so that the measured diffusivities are extracellular parameters. The cell volume fraction in the beads ranged from 0.70 to 0.90, significantly higher than previously reported data. The effective diffusion coefficients conform to the random pore model. No diffusional interaction between acetophenone and phenethyl alcohol was observed. The addition of 2 vol% ethanol or methanol slightly increased the diffusivities. The thermodynamic partition coefficients were measured in the bead‐free water‐organic system and found to be an order of magnitude lower than the values calculated from the analysis of the diffusion data for the organic‐bead system, suggesting that bead‐free equilibrium data cannot be used in triphasic systems. © 1994 John Wiley & Sons, Inc.
Protein separation by differential drainage from foam
Authors: Mohan S. B. , Lyddiatt A. 
Published: December 2004

AbstractCommercially available beer, which is a dilute solution containing components of yeast, malt, and hop used in the manufacture of the beer, was used as a model system to demonstrate the potential of foam fractionation beyond the primary foaming stage. Most of the components present in the beer concentrated in the initial foam, but they drained differentially in the subsequent collapsed foam collected over a period of 30 min. This resulted in further enrichment, in particular, of components which were present in low concentration in the original beer, Preferential drainage from foam, hence, might provide a novel way of fractionating further the proteins concentrated initially in the liquid films of foam. © 1994 John Wiley & Sons, Inc.
Effect of alcohol feeding mode on the biosynthesis of poly (3‐hydroxybutyrate‐co‐3‐hyroxyvalerate)
Authors: Park Chang‐Ho , Damodaran Vijay 
Published: December 2004

AbstractAn alcohol utilizing Alcaligenes eutrophus produced poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) copolymer under phosphate limitation. Fermentation was performed for 42−46 h in a computer‐controlled 5‐L working volume fed‐batch fermentor using ethanol and propanol as carbon sources. The culture experienced phosphate limitation in approximately 19 h. When propanol was used as a sole carbon source, 24 g/L of copolymer with 36.5 mol % of hydroxyvalerate (HV) was produced at a polymer yield of 0.41 g polymer/g alcohol (g/g) and an average polymer production rate of 0.08 g polymer/g residual biomass‐h (g/g‐h). Two experiments switching alcohol after phosphate exhaustion resulted in better polymer production (g/L), polymer yield (g/g) on alcohol, HV yield (g/g) on propanol, and average polymer production rate (g/g‐h) as compared to propanol run without alcohol switching. One switching experiment was from a mixture of 50% ethanol and 50% propanol to 100% propanol and the other experiment was from 100% ethanol to a mixture of 65% ethanol and 35% propanol. Polymer yield for these two experiments was 0.51 g/g and 0.46 g/g, respectively. However, HV mol % in the copolymer for these two runs (30.8 mol % 12.6 mol % respectively) was lower compared to propanol run without alcohol switching (3605 mol %). Direct switch from ethanol to propanol did not support cell growth and polymer production. Polymer production rate and polymer yield changed with time, and the pattern was dependent upon the alcohol feeding mode. © 1994 John Wiley & Sons, Inc.
Cultivation of attenuated hepatitis A virus antigen in a titanium static mixer reactor
Authors: Junker B. H. , Seamans T. C. , Ramasubramanyan K. , Aunins J. , Paul E. , Buckland B. C. 
Published: December 2004

AbstractThe titanium static mixer reactor, demonstrated for a variety of vaccine processes during the late 197s, was investigated for the production of attenuated hepatitis A virus antigen from anchorage‐dependent MRC‐5 cells. This reactor system used Charles River Biotechnological Services cabinets for monitoring and process control. Cell inoculation protocols, using 6000−10,000 cells/cm2, resulted on over 95% attachment at both the laboratory and pilot scales. Indirect monitoring techniques using oxygen, glucose, L‐serine, and L‐glutamine uptake rates were indicative of cell growth prior to virus inoculation as well as environmental and/or nutrient limitations. Seven laboratory‐scale (3900 cm2) runs and one pilotscale (265,000 cm2) run were conducted to investigate refeeding regiments, parallel versus perpendicular element orientation, increased element surface area per unit volume, and scale‐up performance. In general, lysate antigen yields achieved were similar to those of parallel T‐flasks cultivated under similar conditions. © 1994 John Wiley & Sons, Inc.
Antibiotic production by Streptomyces aureofaciens using self‐cycling fermentation
Authors: Zenaitis Michael G. , Cooper David G. 
Published: December 2004

AbstractThe self‐cycling frementation (;rSCF) technique was applied to culture of Streptomyces aureofaciens. SCF is a method of continuous fermentation in which the metabolism of a microorganism is monitored by a measurement such as dissolved oxygen. These data are sent to a computer to allow it to control the system. Tetracycline production was observed only at exceedingly low iron concentrations in the growth medium. Repeatability of cycles was found to be dependent upon the presence of tetracycline in the fermentation broth as well as the strain of microorganism grown in the fermentor. Tetracycline was produced by an improved specific rate when compared to results in the literature for this organism grown using the batch method. © 1994 John Wiley & Sons, Inc.
Correlation between steady‐state cell concentration and cell death of hybridoma cultures in chemostat
Authors: Lee Yuan‐Kun , Yap Peng‐Kang , Teoh Ai‐Peng 
Published: December 2004

AbstractIn the present study, the steady‐state cell density (X) of chemostat cultures of murine hybridoma was varied by the concentration of glucose and glutamine in culture medium and the dissolved oxygen partial pressure. Except at low glutamine and low oxygen levels, the specific death rate (kd) of the cultures was found to decrease with increasing dilution rate (D). However, the plot of kd vs. X/D yielded linear relation, which suggests that cell death was due to a non‐growth‐linked inhibitory product of the cells. The kd value measured at low glutamine and low oxygen levels remained practically unchanged over a wide range of D between 0.020 and 0.029 h−1. The kd for low oxygen cultures was always lower than the values obtained in low glucose and low glutamine cultures. A low‐molecular‐weight component of possibly less than 3000 MW was detected to be cell‐death‐inducing in the supernatant of exponentially growing cultures. It was neither lactate nor ammonium. The autoinhibitor was not cell‐line specific. © 1995 John Wiley & Sons, Inc.
Enzymatic interesterification of triglyceride with surfactant‐coated lipase in organic media
Authors: Goto Masahiro , Goto Muneharu , Kamiya Noriho , Nakashio Fumiyuki 
Published: December 2004

AbstractSeveral surfactant‐coated enzymes have been prepared by coating lipases of various origins with a nonionic surfactant, glutamic acid dioleylester ribitol (2C18Δ9GE). Enzymatic interesterification of tripalmitin with oleic acid using the surfactant‐coated lipase was carried out in organic media. The surfactant‐coated lipases could effectively catalyze the interesterification of glycerides better than did the powder lipases. A suitable organic solvent was an aliphatic hydrocarbon such as isooctane. The enzymatic activity for the interesterification strongly depended on the origin of the lipase. The surfactant‐coated lipase prepared by Mucor javanicus showed the highest enzymatic activity for the interesterification of glycerides, although its powder lipase did not show enzymatic activity. Selective interesterification of glycerides could be performed by adjusting the concentration ratio of oleic acid to tripalmitin in isooctane. Di‐substituted glyceride could be selectively produced when the concentration ratio of carboxylic acid to glycerides was 7. © 1995 John Wiley & Sons, Inc.
An in situ dissolved‐hydrogen probe for monitoring anaerobic digesters under overload conditions
Authors: Strong G. E. , Cord‐Ruwisch R. 
Published: December 2004

AbstractThe concentration of diatomic hydrogen in the liquid phase of an anaerobic digester was used to determine the onset of digester failure induced by substrate overloading. The construction of an inexpensive probe to measure dissolved hydrogen, having a partial pressure detection limit of 30 Pa, is described. An increase in the partial pressure of dissolved hydrogen, from less than 30 Pa to 400 Pa, was observed when the D‐glucose concentration in a laboratory‐scaled digester was increased rapidly to 10 mM. However, when the digester was gradually overloaded, an increase in the dissolved‐hydrogen partial pressure was not observed until after the digester failed. The accumulation of volatile fatty acids and digester failure were observed at dissolved‐hydrogen partial pressures below 30 Pa. © 1995 John Wiley & Sons, Inc.
Buffer exchange using size exclusion chromatography, countercurrent dialysis, and tangential flow filtration: Models, development, and industrial application
Authors: Kurnik Ronald T. , Yu Audrey W. , Blank Gregory S. , Burton Arlene R. , Smith David , Athalye Atul M. , van Reis Robert 
Published: December 2004

AbstractThere are three major methods for buffer exchange of proteins at industrial scale: size exclusion chromatography (SEC), tangential flow filtration (TFF), and countercurrent dialysis (CCD). In order to determine the optimal technology for a given process, a study was done to compare these technologies on a technological and economic basis. This comparison required that new mathematical models be developed which enable the common features of each unit operation to be directly compared. The new concept of a diavolume equivalent for SEC, defined as the inverse of the fractional loading, was also introduced to aid in this comparison. Variables that were examined for each unit operation included range of buffer exchange, dilution of protein solution, yield, buffer requirements, total operating time, throughput, plant space, capital, raw materials, and labor costs. It was found that TFF and CCD have a greater range of buffer exchange than SEC. TFF also provides the advantage that concentration of the protein can readily be accomplished in the same step. For processes of equal batch size and yield, TFF and CCD also provide a two‐ to five‐ fold improvement in each of the remaining variables. The major economic advantage in using TFF and CCD over SEC is the decreased plant size required for manufacturing and thus the longer term use of existing facilities. Situations where SEC (or CCD) would be favored over TFF are when protein denaturation occurs in TFF but does not occur in SEC. © 1995 John Wiley & Sons, Inc.