bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of cloned gene dosage on cell growth and hepatitis B surface antigen synthesis and secretion in recombinant CHO cells
Authors: Pendse Girish J. , Karkare Subhash , Bailey James E. 
Published: December 2004

AbstractThe effect of cloned gene copy number on growth and product formation has been studied in sufficient detail using a Chinese hamster overy (CHO) cell line producing recombinant hepatits B surface antigen (HbsAg). Batch culture experiments were carried out in T flasks in order to characterize cell growth and HbsAg secretion in various clones carrying different numbers of HbsAg gene copies integrated into CHO cell chromosomes. Specific growth rates were found to decrease with increasing gane copy number. Secreted HbsAg concentration and specific HbsAg secretion rates were found to increase with increase in gene copy number. Gene copy numbers in each clone determined using Southern hybridizations were positively correlated with intracellular dihydrofolate reductase (dhfr) content using a flow cytometric assay. The mRNA levels quantitated using Northern hybridization followed by autroadiography and densitometry also gave the same trends. The flow cytometry experiments show that while parental cells were quite homogeneous with respect to intracellular dhfr content, the amplified clones exhibit a great deal of heterogeneity in dhfr content. Pulse‐chase experiments show that the efficiency of HbsAg secretion (defined here as the fraction of initially labeled HbsAg that is secreted into the extracellular medium at the end of a 23.5‐h chase) decreases and also that the intracellular HbsAg degradation increases with increasing gene copy number.
Thermostability of soluble and immobilized α‐amylase from Bacillus licheniformis
Authors: De Cordt S. , Vanhoof K. , Hu J. , Maesmans G. , Hendrickx M. , Tobback P. 
Published: December 2004

AbstractIn view of a possible application of the α‐amylase from Bacillus licheniformis as a time–temperature integrator for evaluation of heat processes,11 thermal inactivation kinetics of the dissolved and covalently immobilized enzyme were studied in the temperature range 90–108°C. The D‐values (95°C) for inactivation of α‐amylase, dissolved in tris‐HCl buffer, ranged from 6 to 157 min, depending on pH, ionic strength, and Ca2+ and enzyme concentration. The z‐value fluctuated between 6.2 and 7.6°C. On immobilization of the α‐amylase by covalent coupling with glutaraldehyde to porous glass beads, the thermoinactivation kinetics became biphasic under certain circumstances. For immobilized enzyme, the D‐values (95°C) ranged between 17 and 620 min, depending largely on certain environmental conditions. The z‐value fluctuated between 8.1 and 12.9°C. In each case of biphasic inactivation, the z‐value of the stable fraction (with the higher D‐values) was lower than the z‐value of the labile fraction. © 1992 John Wiley & Sons, Inc.
Enhanced release of rosmarinic acid from Coleus blumei permeabilized by dimethyl sulfoxide (DMSO) while preserving cell viability and growth
Authors: Park Chang‐Ho , Martinez Blanca C. 
Published: December 2004

AbstractContinuous permeabilization of preconditioned Coleus blumei cells with dimethyl sulfoxide (DMSO) is shown to be an effective strategy for the enhanced release of rosmarinic acid (RA) while preserving cell viability. When nonpreconditioned cells were permeabilized with DMSO, they lost their viability at DMSO concentrations higher than a critical value located between 0.1% and 0.5% DMSO. Product release was low [0.49 g RA/100 g dry cell weight (DCW)] at 0.1% DMSO. Preconditioning cells at 0.1% DMSO ensured high viability at DMSO concentrations of 0.5%, 1.0%, and 1.5%. Product release reached a maximum of 2.85 g RA/100 g DCW at 0.5% DMSO, which was 66.4% of the total rosmarinic acid produced. © 1992 John Wiley & Sons, Inc.
Properties of microfiltration membranes: The effects of adsorption and shear on the recovery of an enzyme
Authors: Bowen W. Richard , Gan Quan 
Published: December 2004

AbstractAn experimental study of the interaction of the enzyme yeast alcohol dehydrogenase (YADH) with microfiltration membranes has been carried out. Most measurements were made with capillary pore inorganic membranes (Anopore) with some comparative measurements being made with polymeric membranes of low protein affinity (Durapore). It has been shown that the prolonged exposure of the enzyme to the inorganic membrane under low‐shear conditions (slow recycle) resulted in a loss of enzyme activity. Under filtration conditions, the membrane permeation rate decreased continuously with time. This decrease could be quantified using the standard blocking filtration law, which describes a decrease in pore volume due to deposition of enzyme on the walls of the pore. No significant loss in activity of permeating enzyme occurred under solution conditions where the enzyme was stable. However, a significant loss of such activity occurred under solution conditions where the enzyme was slightly unstable. The experiments indicate that the likely mechanism for activity loss is a membrane/enzyme interaction resulting from a shear induced deformation of the enzyme structure. Two conclusions of practical importance are drawn from the work. © 1992 John Wiley & Sons, Inc.
Biofilm reactors: An experimental and modeling study of wastewater denitrification in fluidized‐bed reactors of activated carbon particles
Authors: Coelhoso Isabel , Boaventura Rui , Rodrigues Alírio 
Published: December 2004

AbstractA fluidized‐bed biofilm reactor using activated carbon particles of 1.69 mm diameter as the support for biomass growth and molasses as the carbon source is used for wastewater denitrification.The start‐up of the reactor was successfully achieved in 1 week by using a liquor from garden soil leaching as the inoculum and a superficial velocity u0 = 5umf. Typical biofilm thickness is 800 μm; therefore covered activated carbon particles have 3.3 mm in diameter.Reactor hydrodynamics was studied by tracer (KCl solution) experiments. The analysis based on residence time distribution theory involved a model with axial dispersion flow and tracer diffusion with linear adsorption inside the biofilm. Peclet numbers higher than 100 were found, allowing the plug flow assumption for the reactor model.Experimental profiles of nitrate and nitrite species were explained by a kinetic model of two consecutive zero‐order reactions coupled with substrate diffusion inside the biofilm. Under the operating conditons used thick biofilms were obtained working in a diffusion‐controlled regime.Comparison is made with results obtained in the same reactor with sand particles as the support for biomass growth. Activated carbon as the support has the following advantages: good adsorptive characteristics, homogeneous biofilm thickness along the reactor, and easy restart‐up of the reactor. © 1992 John Wiley & Sons, Inc.
Estimation of disruption of animal cells by laminar shear stress
Authors: Born C. , Zhang Z. , Al‐Rubeai M. , Thomas C. R. 
Published: December 2004

AbstractUsing mechanical cell properties measured by micromanipulation, and a model of cell distortion in laminar flow fields, a method has been developed for predicting disruption of animal cells by laminar shear stresses. Predictions of the model were compared with measured losses of cell number and viability of TB/C3 murine hybridomas sheared in a cone and plate viscometer at shear rates up to 3950 s−1, and shear stresses up to 600 Nm−2, achieved by enhancement of viscosity with dextran. In all cases, the experimental, results and predictions were within 30%. Such excellent agreement suggests it might be possible to use micromanipulation measurements of animal cell mechanical properties to predict cell damage in more complex flow fields, such as those in bioreactors. © 1992 John Wiley & Sons, Inc.
An adjustable expression system for controlling growth rate, plasmid maintenance, and culture dynamics
Authors: Ogden Kimberly L. , Davis Robert H. , Taylor Autin L. 
Published: December 2004

AbstractRecombinant bacterial cells express various levels of model product proteins if the genes of interest are regulated by controllable promoters. The level of gene expression influences the growth‐rate differential between plasmid‐bearing and plasmid‐free cells, and thereby affects the culture dynamics of a plasmid‐containing cell population. An expression system has been designed in which host Escherichia coli cells contain the pil operon controlled by a tac promoter; these cells are transformed with plasmids that contain the repressor gene, lacl, for the tac promoter, in combination with an expression system for a model protein, chloramphenicol acetyl tranferase (CAT). Experimental and theoretical results show that plasmid‐bearing cells can be maintained as dominant in continuous cultures without selective pressure when 12% or less of the cells' total protein is the model product protein, CAT. This is because the segment cells produce pili greatly in excess of normal wild‐type levels, and thus have more of a metabolic burden than do the plasmid‐bearng cells that overproduce CAT. However, when the level of the plasmid‐directed CAT expression is increased above 12% of the cells' total protein, the growth rate of the plasmid‐bearing cells decreases to a value lower than that of the segregant cells. Therefore, plasmid‐containing cells lose their selective advantage at this expression level, and cannot be maintained as the dominant cell type in a continuous culture unless antibiotic or other positive selection methods are used. By controlling the growth rate differential of this bacterial host/plasmid system, a variety of interesting competitive culture dynamics is investigated. All experimental measurements for continuous cultures are in very good agreement with theory using kinetic parameters determined from independent batch experiments. © 1992 John Wiley & Sons, Inc.
The extended serial subculture of human diploid fibroblasts on microcarriers using a new medium supplement formulation
Authors: Forestell Sean P. , Kalogerakis Nicolas , Behie Leo A. 
Published: December 2004

AbstractHuman diploid fibroblasts serially passaged on microcarriers exhibit a decrease in their proliferative capacity with each transfer from microcarrier‐to‐microcarrier. This phenomenon, which does not occur in the same time scale with cells cultured in T‐flasks, has been a serious barrier to the systematic utilization of microcarriers in the scale‐up of anchorage‐dependent human diploid cell cultures. This decreases in cell growth with each passage is shown to be related to the serum content of the medium, with high serum concentrations resulting in a more rapid decrease in cell growth with each serial transfer. As a result, methods for reducing the serum requirement of the cells were investigated. A new medium supplement mixture, PPRF92, has been developed, which allows the serial passaging of MRC5 cells on Cytodex 1 microcarriers through as many as 13 microcarrier‐to‐microcarrier tranfers, and at a serum levels as low as 1%, with no decrease in the proliferative capacity of the cells until they approach their reported population doubling limit. This new supplement mixture is a significant improvement to microcarrier technology in that it enables the use of microcarriers in the early stages of inocculum build‐up for the production purposes. © 1992 John Wiley & Sons, Inc.
Mechanical agitation of hybridoma suspension cultures: Metabolic effects of serum, pluronic F68, and albumin supplements
Authors: Smith Craig G. , Greenfield Paul F. 
Published: December 2004

AbstractMetabolic effects of the medium supplements, fetal bovine serum (FBS), Pluronic F68, and bovine serum albumin (BSA) were compared for agitated bioreactor cultures of hybridoma cells. Agitation speeds up to 600 rpm, without entrainment of gas bubbles by sparging or vortex formation, allowed examination of cell interactions with turbulent fluid forces. For cultures in FBS‐supplemented RPMI media, there was no significant effect of intense turbulent fluid shear on cell growth, metabolism, or antibody, production. Serum‐free cultures (Pluronic F68 or BSA supplements) at 600 rpm demonstrated greatly increased glycolysis rates during exponential growth relative to controls. Nutrient limitations caused increased rates of decline of the viable cell concentrations and a reduction in final antibody titers by around 70%. The Pluronic F68 and BSA supplements did not lead to cell protection by modifying metabolism under conditions of intense turbulent fluid shear. Supplementing the protein‐free medium with FBS reduced glycolysis rates in exponential growth phase, but this did not prevent a high rate of viable cell decline and low antibody titers. We concluded that FBS does not have a metabolic effect on cells subjected to intense turbulent fluid shear. Although the agitation conditions employed in this study were more intense than generally required for agitated bioreactor culture of hybridomas, we have demonstrated the importance of considering metabolic effects of turbulent fluid forces on cultures using nutrient‐rich basal media, in addition to the considerations of gas bubble effects described by other workers. © 1992 John Wiley & Sons, Inc.
Activity and stability of an entrapped‐cell system for the Δ1‐dehydrogenation of steroids in organic media
Authors: Pinheiro H. M. , Cabral J. M. S. 
Published: December 2004

AbstractWhole Arthrobacter simplex cells entrapped in κ‐carra‐geenan or in two types of polyurethane foam, or adsorbed on silanized Celite, were tested for the Δ1‐dehydrogenation of hydrocortisone and its derivatives in organic media. Catalytic activity and stability levels were evaluated for the immobilized cells in buffer with 2.5% (vol/vol) methanol, and in three buffer‐saturated solvents (n‐octan‐1‐ol, n‐decan‐1‐ol, and chloroform). The addition of glutamate to the immobilization support stabilized the activity of the immobilized cells in the tested organic media. The system with polyurethane (HYPOL6100)‐entrapped cells (with coimmobilized glutamate) in n‐decan‐1‐ol provided the highest long‐term activity levels. Several factors involved in the polyurethane‐entrapment procedure were also studied. © 1992 John Wiley & Sons, Inc.
Amino acid supplementation decreases plasmid retention in Escherichia coli
Authors: Shu J. , Shuler M. L. 
Published: December 2004

AbstractThe effect of amino acid supplementation on plasmid stability in Escherichia coli B/r was tested experimentally. Comparisons of experimental results to computer‐predicted values were made using a detailed, structured single‐cell model. The plasmid, pDW17 (a pBR322 derivative with a mutated tac promoter controlling the β‐lactamase gene), was used. In chemostat cultures, the amino acid supplemented cultures were always less stable than those grown in minimal medium. This effect was not a growth rate effect, as increasing growth rate imsproves stability for both cultures in minimal medium and in amino acid supplemented medium. The computer model also predicted a decrease in stability due to amino acid supplementation. The model also predicts that amino acid supplementation, combined with moderately strong plasmid‐encoded protein expresion, results in a depletion of low‐molecular‐weight organics compared with plasmid‐free cells. In minimal medium the same level of plasmid‐encoded protein synthesis results in a strong reduction in amino acid pools compared with plasmid‐free cells. With amino acid supplementation the growth differential between plasmid‐bearing and plasmid‐free cells may be due to an “energy limitation,” while in minimal medium the size of the growth rate differential may be due to a “building block” limitation. © 1992 John Wiley & Sons, Inc.
Cell growth on immobilized cell growth factor. 8. Protein‐free cell culture on insulin‐immobilized microcarriers
Authors: Ito Yoshihiro , Uno Tsuyoshi , Liu Shu Qin , Imanishi Yukio 
Published: December 2004

AbstractIn order to develop a new protein‐free cell culture system, microcarriers immobilized with insulin were synthesized. For the synthesis, glass and polyacrylamide beads were treated for the introduction of amino groups on the surface, and insulin was immobilized on the surface by using several method. Anchorage‐dependent cells. mouse fibroblast cells STO and fibroic sarcoma cells HSDM1C1, and the anchorage‐independent cells, mouse hybridoma cells SJK132‐20 and RDP 45/20 were cultivated on the microcarriers immobilized with insulin. The insulin‐immobilized microcarriers did not have any effect on the proliferation of the anchorage independent cells but promoted the growth of anchorage‐dependent cells remarkably. The activity of immobilized insulin was larger than that of free or adsorbed insulin. The repeated use of the insulin‐immobilized microcarrier was possible, and the promotion activity in the the repeated use was greater than that in the use. © 1992 John Wiley & Sons, Inc.
Studies of the cell‐wall properties of Saccharomyces cerevisiae during fermentation
Authors: Bowen W. Richard , Sabuni Hoze A. M. , Ventham Timothy J. 
Published: December 2004

AbstractThe cell‐wall properties of three strains of the yeast Sacharomyces cerevisiae have been experimentally studied at various times during fermentation. The cell walls have been characterized by electrophoretic mobility measurements, from which zeta potentials may be calculated. They have also been characterized by computerized pH titration, which gives direct information on the number and nature of groups in the yeast cell wall. The data have been quantitatively analyzed in three ways. First, a simplified analysis of the electrokinetic data of a type used by previous workers has been applied. Second, such a simplified analysis of the electrokinetic data has been developed more rigorously by means of a two‐dimensional site‐dissociation model of the outer cell wall–solution interface. Third, a description of the yeast cell‐wall electrochemical properties in terms of a three‐dimensional gel model incorporating site dissociation has been developed. The advantages and disadvantages of the three analyses are discussed. Only the three‐dimensional gel model can account simultaneously for both the electrokinetic and pH surface titration data. It provides new insights into the changes that occur to the yeast cell wall during fermentation. © 1992 John Wiley & Sons, Inc.
Effects of nonionic surfactants on the solubilization and mineralization of phenanthrene in soil–water systems
Authors: Laha Shonali , Luthy Richard G. 
Published: December 2004

AbstractThe solubilization and mineralization of 14C‐phenanthrene in soil–water systems was examined with several commercially available surface‐active agents, viz., an alkyl ethoxylate C12E4; two alkylphenol ethoxylate surfactants: C8PE9.5 and C9PE10.5; two sorbitan ethoxylate surfactants: the sorbitan monolaurate (Tween 20) and the sorbitan monooleate (Tween 80); two pairs of nonionic ethoxylate surfactant mixtures: C12E4/C12E23 at a 1:1 ratio, and C12–15E3/C12–15E9 at a 1:3 ratio; and two surfactants possessing relatively high critical micelle concentration (CMC) values and low aggregation numbers: CHAPS and octyglucoside. Surface tension experiments were performed to evaluate surfactant sorption onto soil and the surfactant doses required to attain the CMC in the soil–water systems. Surfactant solubilization of 14C‐phenanthrene commenced with the onset of micellization. The addition of surface‐active agents was observed not to be beneficial to the microbial mineralization of phenanthrene in the soil–water systems and, for supra‐CMC surfactant doses, phenanthrene mineralization was completely inhibited for all the surfactants tested. A comparison of solubilization, surface tension, and mineralization data confirms that the inhibitory effect on microbial degradation of phenanthrene is related to the CMC of the surfactant in the presence of soil. Additional tests demonstrated the recovery of mineralization upon dilution of surfactant concentration to sub‐CMC levels, and a relatively high exit rate for phenanthrene from micelles. These tests suggest that the inhibitory effect is probably related to a reversible physiological surfactant micelle–bacteria interaction, possibly through partial complexing or release of membrane material with disrupting membrane lamellar structure. This study indicates that nonionic surfactant solubilization of sorbed hydrophobic organic compounds from soil may not be beneficial for the concomitant enhancement of soil bioremediation. Additional work is needed to address physicochemical processes for bioavailability enhancement, and effects of solubilizing agents on microorganisms for remediation and treatment of hydrophobic organic compounds and nonaqueous phase liquids. © 1992 John Wiley & Sons Inc.
Separation of egg yolk immunoglobulins using an automated liquid chromatography system
Authors: Fichtali J. , Charter E. A. , Lo K. V. , Nakai S. 
Published: December 2004

AbstractAn automated liquid chromatography system was developed to carry out the separation of an egg yolk immunoglobulin (IgY) using cation exchange media. Industrially separated egg yolk was diluted 10 times with distilled water, the pH adjusted to 5.5, and the water‐soluble protein fraction separated from lipoproteins by sedimentation. The supernatant was filtered and then applied to a column packed with a cation exchanger within an automated liquid chromatography system. Different operating conditions were investigated using phosphate buffer in order to assess the effect on recovery and purity. Fractions as pure as 80% could be collected and a recovery of the chromatography step of about 65% was obtained for a purity of 60% using either a linear or step gradient. The overall recovery for the process was 34% if one‐step dilution/extraction is used for lipoprotein separation by sedimentation, and 51% if two‐step dillution/extraction is used. Further improvement of the yield to about 60% is possible using centrifugation for lipoprotein separation. The automated system confers many advantages, the key elements being the time savings and accurate control of the process. © 1992 John Wiley & Sons, Inc.
Evolutionary operation (EVOP) to optimize three‐dimensional biological experiments
Authors: Banerjee Rintu , Bhattacharyya B. C. 
Published: December 2004

AbstractEvolutionary operation (EVOP) is used as an efficient technique for optimization of three variable experimental parameters using two‐level factorial designs with center points. For metabolic function like enzyme synthesis by microorganisms, small amounts of metal ions, surfactants, and vitamins act as inducers. The desired quantities of these chemicals are, however, species dependent and have to be found out or each microorganism. By employing the EVOP technique, the requirements of these chemicals have been optimized for the production of protease by Rhizopus oryzae (RO, IIT KGP). © 1993 John Wiley & Sons, Inc.