bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biospecific adsorption of lysozyme onto monoclonal antibody ligand immobilized on nonporous silica particles
Authors: Liapis A. I. , Anspach B. , Findley M. E. , Davies J. , Hearn M. T. W. , Unger K. K. 
Published: December 2004

AbstractIt is very important to understand the equilibrium and dynamic characteristics of biospecific adsorption (affinity chromatography) for both scientific and application purposes. Experimental equilibrium and dynamic column data are presented on the adsorption of lysozyme onto antibody immobilized on nonporous silica particles. The Langmuir model is found to represent the equilibrium experimental data satisfactorily, and the equilibrium association constants and heats of adsorption have been estimated for two systems with different ligand densities. The effects of nonspecific interactions are more pronounced in the system with low‐density ligand. The dynamic interaction kinetic parameters are estimated by matching the predictions of a fixed‐bed model with the experimental breakthrough curves. The agreement between theory and experiment is good for the initial phases of breakthrough, where the mechanism of biospecific adsorption is dominant. In the later phase (saturation neighborhood) of breakthrough, the effects of nonspecific interactions appear to be greater in the low‐density ligand system. The kinetics of the nonspecific interactions were estimated from the data of the later phase of breakthrough and were found to be considerably slower than those attributed to biospecific adsorption.
A structured kinetic modeling framework for the dynamics of hybridoma growth and monoclonal antibody production in continuous suspension cultures
Authors: Batt Brian C. , Kompala Dhinakar S. 
Published: December 2004

AbstractA structured kinetic model is developed to describe the dynamics of hybridoma growth and the production of monoclonal antibodies and metabolic waste products in suspension culture. The crucial details of known metabolic processes in hybridoma cells are incorporated by dividing the cell mass into four intracellular metabolic pools. The model framework and structure allow the dynamic calculation of the instantaneous specific growth rate of a hybridoma culture. The steady state and dynamic simulations of the model equations exhibit excellent agreement with experimentally observed trends in substrate utilization and product formation. The model represents the first to include any degree of metabolic detail and structure in describing a hybridoma culture. In so doing, it provides the basic modeling framework for incorporating further details of metabolism and can be a useful tool to study various strategies for enhancing hybridoma growth as well as viability and the production of monoclonal antibodies in suspension cultures.
Oxygen diffusivity in gel beads containing viable cells
Authors: Kurosawa Hiroshi , Matsumura Masatoshi , Tanaka Hideo 
Published: December 2004

AbstractThis article proposes a simple steady‐state method for measuring the effective diffusion coefficient of oxygen (De) in gel beads entrapping viable cells. We applied this method to the measurement of De in Ca‐ and Ba‐alginate gel beads entrapping Saccharomyces cerevisiae and Pseudomonas ovalis. The diffusivity of oxygen through gel beads containing viable cells was measured within an accuracy of ±7% and found not to be influenced by cell density (0–30 g/L gel), cell type, and cell viability in gel beads. The oxygen diffusivity in the Ca‐alginate gel beads was superior to that of the Ba‐alginate gel beads, and the De in the Ca‐alginate gel beads nearly equalled the molecular diffusion coefficient in the liquid containing the gel beads. The oxygen concentration profile in a single Ca‐alginate gel bead was calculated and compared to the distribution of mycelia of Aspergillus awamori grown in that gel bead. This procedure indicated that the oxygen concentration profile is useful for the estimation of the thickness of the cell layer in a gel bead. Numerical investigation revealed that high effectiveness factors, greater than 0.8, could be obtained using microgel beads with a radius of 0.25 mm.
Alginate concentration: A key factor in growth of temperature‐sensitive baculovirus‐infected insect cells in microcapsules
Authors: King G. A. , Daugulis A. J. , Goosen M. F. A. , Faulkner P. , Bayly D. 
Published: December 2004

AbstractThe desire to increase cell density and product concentration has been the primary driving force for the development of better animal cell culture processes. In the technique used in our laboratory—microencapsulation—insect cells (Spodoptera frugiperda), infected with a temperature‐sensitive mutant of the Autographa californica nuclear polyhedrosis virus (AcNPV), were cultured in multiple membrane alginate–polylysine (PLL) microcapsules which had a controlled membrane molecular‐weight cutoff and an intracapsular alginate concentration which was ca. 16% lower than that obtained in the commercially available single‐membrane system. Cell culture experiments indicated that the intracapsular alginate concentration appears to be a key factor in achieving good cell growth. It was possible to obtain intracapsular cell densities of 8 × 107 cells/mL capsules and virus concentrations to 109 IFU/mL capsules. The virus litre in the supernatant was ca. 300 times lower, indicating that virtually all of the virus was retained within the capsules.
Effects of paddle impeller geometry on power input and mass transfer in small‐scale animal cell culture vessels
Authors: Aunins John G. , Woodson Bruce A. , Hale Timothy K. , Wang Daniel I. C. 
Published: December 2004

AbstractProcess scaleup for stirred‐tank animal cell cultures such as suspension and microcarrier cultures often begins at the bench scale in small spinner vessels. In order to initiate process development under the proper conditions, it is essential to know the physical conditions under which the cells are grown. In this article, power inputs and surface oxygen transfer rates to culture medium in 500‐mL Corning spinner vessels were determined as a function of the impeller geometry, impeller height, and agitation speed. The results obtained indicate that power dissipation dependency differs from literature correlations and may compromise scale up at constant power input from these vessels. These results are of general utility to researchers using small‐scale vessels.
Continuous microbial desulfurization of coal—application of a multistage slurry reactor and analysis of the interactions of microbial and chemical kinetics
Authors: Uhl W. , Höne H.‐J. , Beyer M. , Klein J. 
Published: December 2004

AbstractMicrobial desulfurization of coal by pyrite oxidizing bacterial enrichment cultures has been studied in air‐agitated slurry reactors of 4‐ and 20‐L volumes. Batch experiments showed that inoculation with an active bacterial culture is essential to minimize the lag phase, although a considerable number of pyrite oxidizing bacteria was found on the coal prior to desulfurization. For detailed investigations of kinetics, energy requirements, and technical applicability, a bioreactor equipment consisting of a cascade of eight stages was developed and operated continuously. Microbial desulfurization of coal—monitored by measuring the axial profile of dissolved iron concentration, real and maximum oxygen consumption rates, and cell concentration—at pulp densities to 30% was performed over a period of 200 days without any disturbances concerning the aeration system, fluidization, transport of solids and microbial growth. At a pulp density of 20%, a pyrite conversion of 68% was achieved after the third reactor stage at a total residence time of five days in the first three stages. The kinetics of pyrite degradation were found to be well described by a rate equation of first order in pyrite surface area concentration if the pyrite is directly accessible for microbial attack. Rate constants were determined to 0.48 mg pyrite/(cm2 day) in the first and to 0.24 mg pyrite/(cm2 day) in the following reactor stages. Kinetic models taking into account adsorption/desorption as well as growth kinetics failed to describe the observed reaction rates. However, a model treating pyrite degradation and microbial growth kinetics formalistically seems to be applicable when backmixing between the reactor stages can be avoided. The advantage of a multistage reactor in comparison to single‐stage equipment was shown by calculation. To obtain a pyrite conversion of 68%, a three‐stage reactor would require only 58% of the volume of single‐stage equipment.Measurement of oxygen consumption rates proved to provide quickly and easily measurable parameters to observe microbial coal desulfurization in technical scale: the real oxygen consumption rate is correlated to the pyrite oxidation rate and the maximum oxygen consumption rate is correlated to the concentration of viable cells. The Yo/s coefficient for the amount of oxygen consumed per mass unit of pyrite oxygen was determined to approximately 0.33 in comparison to 1.0 which can be calculated from stoichiornetry. This could yet not be explained. Chemical leaching experiments as well as sulfur analyses of desulfurized coal samples showed that the microorganisms play the main role in degradation of pyrite from coal and that pyrite oxidation by ferric iron can be neglected.
Cellular plasmid content and cloned‐gene expression: Some useful equations
Authors: Satyagal Vasuki N. , Agrawal Pramod 
Published: December 2004

AbstractCellular plasmid content determines the yield of closed‐gene product, affects plasmid replication, and influences the behavior of the culture by dictating the extent of metabolic burden on the host cell and plasmid segregation at cell division. Hence, it is a variable of primary importance in the study of recombinant cell cultures. In this article, equations are developed to enable the conversion of experimental determinations of cellular plasmid content into theoretically important units. The importance of different units in characterizing plasmid effect on cell response is highlighted. Also, equations that relate cellular plasmid content to cloned‐gene expression are developed and successfully tested on several sets of data from literature.
Encapsulation of mammalian cell with chitosan‐CMC capsule
Authors: Yoshioka Toshimitsu , Hirano Ryogo , Shioya Toshiaki , Kako Masatoshi 
Published: December 2004

AbstractViable hybridoma cells were encapsulated. The capsules were formed in one step by placing a drop of cell suspension mixed with negatively charged carboxymethylcellulose (CMC) into a positively charged chitosan solution through the interpolymeric ionic interaction between two oppositely charged polymers. These capsules were found to have a mean diameter of about 1. 5 mm and wall thickness of 3 μm. The cells grew in the capsules using supplemented DMEM/F12 (four kinds of growth factor). The maximum cell density in encapsulating cell culture reached 1 × 107 cells/ml, 10 times higher than that obtained in the free cell culture. The maximum monoclonal antibody concentration in the free cell culture was 15μg/mL, but that in the capsule was 45μg/mL The antibody produced by the cell was concentrated about four times higher inside than outside of the capsules.
Immobilization of Arthrobacter simplex in a thermally reversible hydrogel: Effect of temperature cycling on steroid conversion
Authors: Park Tae Gwan , Hoffman Allan S. 
Published: December 2004

AbstractArthrobacter simplex cells, which convert the steroid hydrocortisone to prednisolone, have been entrapped in a thermally reversible hydrogel. Such hydrogels exhibit a lower critical solution temperature (LCST) wherein the gel shrinks and deswells when it is warmed through its LCST, and then reversibly expands and reswells when it is cooled below the LCST. The immobilized cell‐hydrogel system has been thermally cycled between two temperatures, each below the LCST. The upper temperature was selected to be just below the LCST, where the gel deswells but does not collapse, as it does at the LCST. The thermal cycling acts like a “hydraulic pump” which enhances mass transfer of the substrate (hydrocortisone) in and the product (prednisolone) out of the gel, thereby increasing steroid conversion dramatically relative to isothermal operation at either the upper or lower temperature. The increased conversion can also be due in part to reduced product inhibition. Mass transfer resistance and product inhibition are among the most serious problems in immobilized biocatalyst technology and thermal cycling of LCST hydrogels is both a novel and useful approach to minimizing these problems.
Dynamic analysis of genetic control and regulation of amino acid synthesis: The tryptophan operon in Escherichia coli
Authors: Sen Asok K. , Liu Wei‐Min 
Published: December 2004

AbstractA mathematical model of the tryptophan operon is analyzed to investigate the regulatory effects of feedback repression and the demand for tryptophan in the cell. In this model, feedback repression is considered to be a two‐step process. First, the endproduct tryptophan combines with the inactive repressor produced by the regulatory genes to yield an active complex. This complex subsequently binds to the operator and prevents transcription of the structural genes into mRNA. The demand for tryptophan in the cell is modeled by a hyperbolic saturation function of the Michaelis‐Menten type. Results are obtained for the expression of the tryptophan operon in Escherichia coli and their applicability to tryptophan production by microbial fermentation is discussed. It is shown that, depending on the strain level of the operon and the rate of utilization of tryptophan in the cell, an overproduction of tryptophan can be achieved under stable operating conditions; in other circumstances, the operon may become stable or unstable, and may lead to a periodic synthesis.
A liquid emulsion membrane process for the separation of amino acids
Authors: Itoh H. , Thien M. P. , Hatton T. A. , Wang D. I. C. 
Published: December 2004

AbstractThe method of using liquid emulsion membranes featuring the cation carrier D2EHPA [di‐(2‐ethylhexyl) phosphoric acid] for the separation of L‐phenylalanine is examined. Results from experiments performed under various conditions are discussed and an optimal condition for separation is determined. The selectivity of the liquid emulsion membrane system is discussed. The effects of impurities such as sodium chloride, glucose, lactic acid, and L‐tryptophan on the transport of L‐phenylalanine are evaluated. It is shown that the liquid emulsion membrane system is a potential operation not only to separate L‐phenylalanine but also concentrate it with great efficiency.
Bovine colostrum or milk as a serum substitute for the cultivation of a mouse hybridoma
Authors: Ramírez O. T. , Sureshkumar G. K. , Mutharasan R. 
Published: December 2004

AbstractA mouse–mouse hybridoma was grown in serum‐free medium supplemented with bovine milk or colostrum. Bovine colostrum supported growth of the hybridoma whereas bovine milk alone did not support cellular proliferation. For growth in medium supplemented with colostrum, the maximum cell concentration achieved was 1.4 × 106 cells/mL in 2.2% colostrum, which is 44% of that obtained in 9% serum. When cells were grown in media containing milk and low amounts of serum (<1%) the maximum cell concentration in 2.2% milk with 0.4% serum was 2 × 106 cells/ml, whereas it was only 0.2 × 106 cells/ml and 1.3 × 106 cells/ml in 2.2% milk alone and 0.4% serum alone, respectively. Similar behavior was observed for growth in media containing colostrum and low amounts of serum. The monoclonal antibody production in media containing combinations of serum and milk or colostrum was comparable to that obtained in media with higher serum concentrations. Experiments performed with conditioned media suggest that the rapid decrease in viability, after the maximum cell concentration has been reached, is partially due to the presence of some inhibitory components generated during the cell culture rather than due to depletion of some serum components.
Batch and continuous cultivation of Pseudomonas fluorescens at increased pressure
Authors: Onken Ulfert 
Published: December 2004

AbstractThe effect of increased total pressure and partial pressures of oxygen and carbon dioxide on the growth of Pseudomonas fluorescens was investigated in an airlift reactor. In batch cultivations bacterial growth was completely inhibited with air at 8 bars total pressure. The same effect was observed with aeration by pure oxygen at 1.15 bars. Carbon dioxide partial pressure did not show inhibitory effects. Continuous experiments confirm the assumption that growth inhibition at higher total pressure is caused by the increase in oxygen partial pressure. Incubation of P. fluorescens at higher oxygen partial pressure led to an increase of bacterial productivity during subsequent continuous cultivation at ambient pressure (1 bar) with air. Maximum productivity was increased by about 75% after aeration with pure oxygen. This effect is probably the result of metabolic adaption of the bacterial cells to high oxygen partial pressure.
Ecoengineering high rate anaerobic digestion systems: Analysis of improved syntrophic biomethanation catalysts
Authors: Thiele Jurgen H. , Wu Wei‐Min , Jain Mahendra K. , Zeikus J. Gregory 
Published: December 2004

AbstractHigh performance biomethanation granules with operational specific COD removal rates of 7 kg COD removed/kg SS/d were obtained by ecoengineering conventional, granular, UASB digester sludge using a designed protocol of starvation and selection on a defined volatile fatty acid (VFA) based mineral medium. Addition of low (0.15 mM) sulfate levels to this VFA medium increased the maximum shock‐load COD removal rate of the ecoengineered biomethanation granules to 9 kg COD/kg SS/d with specific acetate, propionate, and butyrate removal rates of 111, 28, and 64 mol/g SS/d. Addition of moderate (26 mM) calcium levels inhibited growth and altered the structure of granules. The general cellular, growth, stability, and performance features of these ecoengineered granules are described and discussed in relation to their use as improved biomethanation starter cultures.
Hydrodynamics and mass transfer in two‐phase aqueous extraction using spray columns
Authors: Sawant S. B. , Sikdar S. K. , Joshi J. B. 
Published: December 2004

AbstractSpray columns can be used to isolate and purify proteins using the two‐phase aqueous extraction technique based on polyethylene glycol (PEG) and dextran. The fractional dispersed phase (PEG) holdup and overall mass transfer coefficients were measured in a 9.7 mm i.d. spray column. We found that the dispersed phase holdup increased with increasing PEG phase velocity. The overall mass transfer coefficients for bovine serum albumin, normalized for the PEG holdup, were found to be independent of the PEG phase velocity. This result was expected, since true mass transfer coefficients do not vary with phase velocity.
A bioenergetic model of a mixed production fermentation
Authors: Haughney H. A. , Nauman E. B. 
Published: December 2004

AbstractA bioenergetic model has been developed for the fermentation of glucose by Bacillus polymyxa. This model uses energy balances to determine which pathways are utilized by the substrate. The model can predict substrate consumption, biomass formation, and the product distribution for this fermentation. The products are carbon dioxide, water, 2,3‐butanediol, and ethanol, where ethanol represents lumped anaerobic products.
Cell volume measurement as an estimation of mammalian cell biomass
Authors: Frame Kelly K. , Hu Wei‐Shou 
Published: December 2004

AbstractMeasurements of volume distributions and dry weight are made on hybridoma cells in culture. The volume of viable hybridoma cells is significantly larger than that of nonviable cells. During exponential growth, the volume of the viable hybridoma cells is found to be significantly larger than that during other stages of batch culture. Proportionality is found between the volume of the cells and their dry weight, indicating that the volume data can be used in conjunction with cell concentration data as a practical technique for indirect measurement of the biomass concentration present in a culture. Comparison of dry weight concentrations in continuous culture to predictions from the volume data shows very good agreement.
Characterization of an immobilized cell, trickle bed reactor during long term butanol (ABE) fermentation
Authors: Park Chang‐Ho , Okos Martin R. , Wankat Phillip C. 
Published: December 2004

AbstractAcetone–butanol–ethanol (ABE) fermentation was performed continuously in an immobilized cell, trickle bed reactor for 54 days without, degeneration by maintaining the pH above 4.3. Column clogging was minimized by structured packing of immobilization matrix. The reactor contained two serial glass columns packed with Clostridium acetobutylicum adsorbed on 12‐ and 20‐in.‐long polyester sponge strips at total flow rates between 38 and 98.7 mL/h. Cells were initially grown at 20 g/L glucose resulting in low butanol (1.15 g/L) production encouraging cell growth. After the initial cell growth phase a higher glucose concentration (38.7 g/L) improved solvent yield from 13.2 to 24.1 wt%, and butanol production rate was the best. Further improvement in solvent yield and butanol production rate was not observed with 60 g/L of glucose. However, when the fresh nutrient supply was limited to only the first column, solvent yield increased to 27.3 wt% and butanol selectivity was improved to 0.592 as compared to 0.541 when fresh feed was fed to both columns. The highest butanol concentration of 5.2 g/L occurred at 55% conversion of the feed with 60 g/L glucose. Liquid product yield of immobilized cells approached the theoretical value reported in the literature. Glucose and product concentration profiles along the column showed that the columns can be divided into production and inhibition regions. The length of each zone was dependent upon the feed glucose concentration and feed pattern. Unlike batch fermentation, there was no clear distinction between acid and solvent production regions. The pH dropped, from 6.18–6.43 to 4.50–4.90 in the first inch of the reactor. The pH dropped further to 4.36–4.65 by the exit of the column. The results indicate that the strategy for long term stable operation with high solvent yield requires a structured packing of biologically stable porous matrix such as polyester sponge, a pH maintenance above 4.3, glucose concentrations up to 60 g/L and nutrient supply only to the inlet of the reactor.
Indirect electrochemical reduction of methemoglobin: Design of the process
Authors: Labrune P. , Bergel A. , Comtat M. 
Published: December 2004

AbstractMethemoglobin can be reduced on a platinum cathode using flavin mononucleotide as an oxido‐reduction mediator. The process requires the utilization of a filter‐press cell with compartments separated by a semi‐permeable membrane. Analysis of the various constraints imposed by the process itself and by the nature of the molecules involved shows that the electrolysis cell must operate at a low temperature, in strictly anaerobic conditions, in series with a storage tank, and with fluid circulation rates lower than approximately 0.8 m/s. A process has been designed that takes into account these imperatives and enables volumes of solution of the order of 200 cm3 to be processed. It enables optimization of the flow rates used as well as of the methemoglobin/flavin ratio and is the forerunner of an industrial reactor.