bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of immobilization procedure and salt environment on functional stability of chloroplast membranes: Experimental data and numerical analysis
Authors: Thomasset Brigitte , Thomas Daniel , Lortie Robert 
Published: December 2004

AbstractThe interactions between chloroplast membranes and their microenvironment within artificial matrices (albumin‐glutaraldehyde matrix, polyurethane foam) where investigated. Particularly, the influence of a high‐ionic‐strength medium (0.75 M potassium citrate) on the stability of the photosynthetic ferricyanide reduction by immobilized thylakoids has been studied. A method of data analysis based on a nonlinear identification method combined with the numerical integration of the equation of the transient state of the continuous stirred tank reactor (CSTR) is proposed to estimate the actual degradation of the photosynthetic electron transfer. A statistical analysis achieved on the parameter values has allowed a quantitative assessment of the global behavior of immobilized chloroplast membranes. From the mathernatical analysis of the experimental data, we demonstrate that citrate used in the reaction media prevents the photoinactivation of the electron transfer chain whatever the nature of the matrix or the type of the reactor. The use of an albumin‐glutaraldehyde matrix or an open reactor during experiments also has allowed a better stabilization of the photosystems under operational conditions.
Bacterial removal of pyrite from concentrated coal slurries
Authors: Andrews G. , Darroch M. , Hansson T. 
Published: December 2004

AbstractTo be economically feasible, bacterial coal desulfurization must be done at a high rate in concentrated coal slurries. The rate may be restricted by gas transfer limitation (O2 or CO2), inhibition of the Thiobacilli, or ceil death by mechanical abrasion. Experiments designed to differentiate between these limitations show that CO2 transport is limiting in shake flasks for slurries of more than 20% (wt/wt) of a coal containing 1% pyritic sulfur. Air sparging removed this limitation in slurries of up to 50%, leaving inhibition as the main limitation. Heterotrophic bacteria that establish themselves in a recycled cell culture increase process rates not only by removing organic inhibitors but also by increasing the O2–CO2 ration required by the biomass to the value that is supplied naturally from air.
Protein enrichment of sweet potato residue with amylolytic yeasts by solid‐state fermentation
Authors: Yang Shang‐Shyng 
Published: December 2004

AbstractStarchy agricultural wastes were inoculated with amylolytic yeasts for protein enrichment by solid‐state fermentation. The moisture content of substrate was 65–69%, and water activity was equivalent to 0.98–0.99. The optimum conditions for protein enrichment were initial moisture content 65%, initial pH 4.5, a 1:1 mixture of ammonium sulfate and urea was incrementally added to the ferment with 1% added at zero time, 1% added at 24 h, and 0.5% added at 48 h, and incubation with amylolytic yeasts (1.0 × 1010/100 g substrate) at 30°C for 2–3 days. The final product contained 16.11–20.82% protein.
A kinetic analysis of hybridoma growth and metabolism in batch and continuous suspension culture: Effect of nutrient concentration, dilution rate, and pH
Authors: Miller W. M. , Blanch H. W. , Wilke C. R. 
Published: December 2004

AbstractHybridomas are finding increased use for the production of a wide variety of monoclonal antibodies. Understanding the roles of physiological and environmental factors on the growth and metabolism of mammalian cells is a prerequisite for the development of rational scale‐up procedures. An SP2/0‐derived mouse hybridoma has been employed in the present work as a model system for hybridoma suspension culture. In preliminary shake flask studies to determine the effect of glucose and glutamine, it was found that the specific growth rate, the glucose and glutamine metabolic quotients, and the cumulative specific antibody production rate were independent of glucose concentration over the range commonly employed in cell cultures. Only the specific rate of glutamine uptake was found to depend on glutamine concentration. The cells were grown in continuous culture at constant pH and oxygen concentration at a variety of dilution rates. Specific substrate consumption rates and product formation rates were determined from the steady state concentrations. The specific glucose uptake rate deviated from the maintenance energy model1at low specific growth rates, probably due to changes in the metabolic pathways of the cells. Antibody production was not growth‐associated; and higher specific antibody production rates were obtained at lower specific growth rates. The effect of pH on the metabolic quotients was also determined. An optimum in viable cell concentration was obtained between pH 7.1 and 7.4. The viable cell number and viability decreased dramatically at pH 6.8. At pH 7.7 the viable cell concentration initially decreased, but then recovered to values typical of pH 7.1–7.4. Higher specific nutrient consumption rates were found at the extreme pH values; however, glucose consumption was inhibited at low pH. The pH history also influenced the behavior at a given pH. Higher antibody metabolic quotients were obtained at the extreme pH values. Together with the effect of specific growth rate, this suggests higher antibody production under environmental or nutritional stress.
Oxygen transfer properties of a bioreactor for use within a nuclear magnetic resonance spectrometer
Authors: Drury David D. , Dale Bruce E. , Gillies Robert J. 
Published: December 2004

AbstractNuclear magnetic resonance (NMR) spectroscopic analysis of whole cells is an important emerging technique for noninvasive and nondestructive monitoring of cell physiology. However, this technique requires extremely high cell densities. Attempts to maintain densities above the carrying capacity of a maintenance system result in the demise of the entire culture. To define conditions for maintaining mammalian cells at high densities for NMR studies, we have designed a bioreactor to operate under defined, oxygen‐limited conditions within an NMR spectrometer. The bioreactor utilizes hollow fibers to deliver nutrients and remove wastes from an agitated cell suspension. The mass transfer properties of the fibers with respect to oxygen were determined. Ehrlich Ascites Tumor (EAT) cells were supplied with glutamine as the respiratory carbon source. The maximum viable cell density supported by a given oxygen concentration in the fluid flowing through the fiber lumen was predicted and then confirmed experimentally on the bench and in the spectrometer.
Physical mechanisms of cell damage in microcarrier cell culture bioreactors
Authors: Cherry Robert S. , Papoutsakis Eleftherios Terry 
Published: December 2004

AbstractThe negative effects of excessive agitation on tissue cells in microcarrier culture have often been ascribed to “shear.” Analysis of the fluid mechanics occurring suggests that there are actually three potential damage mechanisms: collisions of a cell‐covered microcarrier with other beads, collisions with parts of the reactor (primarily the impeller), and interaction with turbulent eddies the size of the microcarrier beads. Review of the available quantitative information on agitation effects in cell cultures does not establish which mechanism is predominant; the range of experimental variables reported emphasizes power input over the other reactor and impeller parameters. The bead–bead collision model is tentatively supported by the available data, but the other mechanisms may still be significant in some systems. The formation of bead aggregates by cellular bridging provides a parallel means of damaging cells. Breaking of these bridges by any of the three means identified earlier can cause cell destruction and/or the net transfer of cells to formerly bare beads. High concentrations of bridges are favored by lower agitation rates, presumably because the bridges are not as quickly destroyed after formation.
Serum‐free media in hybridoma culture and monoclonal antibody production
Authors: Glassy Mark C. , Tharakan John P. , Chau Pao C. 
Published: December 2004

AbstractThe replacement of serum in hybridoma cultures is considered. The focus is on the effects of serum‐free media on hybridoma growth and monoclonal antibody secretion. Comparative literature data with serum supplemented cultures are discussed with an analysis of serum‐free formulations and selection rules for the serum‐free ingredients. In general, serum‐free media which are “lipid rich” can sustain cell growth rates approaching that of serum supplemented cultures. Specific antibody secretion rate, however, is usually higher in serum‐free media, irrespective of the lipid content.
Reductive dissolution of fe(III) oxides by Pseudomonas sp. 200
Authors: Arnold Robert G. , DiChristina Thomas J. , Hoffmann Michael R. 
Published: December 2004

AbstractThe kinetics and mechanism of reductive dissolution of Fe(III) oxides were examined in pure, batch cultures of Pseudomonassp. 200. Primary factors controlling hematite dissolution kinetics were mineral surface area (or concentration of high‐energy surface sites), ligand concentration, and cell number. In the presence of nitrilotriacetic acid (NTA), saturation kinetics were apparent in the relationship governing reductive dissolution of hematite. A kinetic expression was developed in which overall iron‐reduction rate is functionally related to the concentrations of both NTA and Fe(III).Addition of NTA resulted in a 20‐fold increase in the microbial rate of mineral (reductive) dissolution. Mechanisms in which NTA served as a bridging ligand, shuttling respiratory electrons from the membrane‐bound microbial electron transport chain to the metal center of the iron oxide, or accelerated the departure of Fe(II) centers (bound to ligand) from the oxide surface following reduction have been postulated. Experimental results indicated that cell–mineral contact was essential for reductive dissolution of goethite.
Cellulase immobilization on Fe3O4 and characterization
Authors: Garcia Albert , Oh Sangha , Engler Cady R. 
Published: December 2004

AbstractA successful procedure for attaching cellulase to 45 μm iron oxide particles with a high‐molecular‐weight (1000) ligand has been developed. Mass and activity balances were calculated for immobilized enzymes with different loadings. The highest specific activity of the immobilized enzyme was 5.9 mmol glucose/g bound protein/h. The efficacy of retaining enzymatic activity was 128%. The optimum pH was 5.5 compared to 4.0 of the free enzyme. The half‐life of the IMC was extended to 272 h compared to 0.77 h of the free enzyme.
Peptide synthesis with immobilized carboxypeptidase Y
Authors: Cramer Steven M. , Horváth Csaba 
Published: December 2004

AbstractEnzymatic peptide synthesis was investigated using carboxypeptidase Y immobilized with glutaraldehyde on 10 μm microparticulate amino‐silica. Carboxypeptidase Y was immobilized with 98.5% recovery of active enzyme to yield the immobilized enzyme having 0.55 units esterase activity/mg amino‐silica support. The stability of the immobilized enzyme was examined as a function of pH, temperature, and reactant concentrations. Immobilized Carboxypeptidase Y was used in stirred batch and recirculating packed‐bed reactors for peptide synthesis. Packed‐bed reactors (40 × 4.6 mm, 60 × 4.6 mm) were used to catalyze the synthesis of 170 mg N‐benzoyl‐L‐arginyl‐L‐methioninamide, 380 mg N‐benzoyl‐L‐arginyl‐L‐methionyl‐L‐leucinamide, and 200 mg N‐benzoyl‐L‐arginyl‐L‐methionyl‐L‐leucyl‐L‐phenylalaninamide in 8, 3, and 1 hour, respectively, as intermediates in the synthesis of L‐methionyl‐L‐leucyl‐L‐phenylalanine. No inactivation of the immobilized enzyme was observed during the course of the reactions. The N‐benzoyl‐L‐arginyl group served to increase the water solubility of the peptides and was removed by immobilized trypsin at the end of synthesis to obtain the final product. While the first two syntheses were conducted with aqueous reaction mixtures, the synthesis of N‐benzoyl‐L‐arginyl‐L‐methionyl‐L‐leucyl‐L‐phenylalaninamide was carried out in a reaction mixture containing dimethylformamide to avoid precipitation of the product. HPLC and amino acid analysis confirmed the high purity and amino acid composition of the final product.
Hydrolysis of lactose in skim milk by immobilized β‐galactosidase in a spiral flow reactor
Authors: Bakken Andrew P. , Hill Charles G. , Amundson Clyde H. 
Published: December 2004

Abstractβ‐galactosidase from Aspergillus Oryzae immobilized in a spiral flow reactor was used to effect the hydrolysis of the lactose component of skim milk. Residence time distribution measurements were used to assess the amount of longitudinal dispersion occurring as a consequence of the spiral flow pattern and the semiporous nature of the polymeric material used to construct the spiral. It was possible to model the flow conditions as tubular flow with a Peclet number that was a linear function of the reactor space time. Nonlinear regression methods were used to determine the kinetic parameters of three proposed enzymatic rate expressions. The best fit of the data was obtained using a rate expression containing separate terms for competitive inhibition of the reaction by both the a and β anomers of galactose. This kinetic model also incorporates the kinetics of the mutarotation between these forms. At 30°C and a space time of 7 minutes, 80% of the lactose present in skim milk can be converted to glucose and galactose.
In vivo nuclear magnetic resonance analysis of immobilization effects on glucose metabolism of yeast Saccharomyces cerevisiae
Authors: Galazzo Jorge L. , Bailey James E. 
Published: December 2004

AbstractFermentation rates and intracellular compositions have been determined for alginate‐entrapped Saccharomyces cerevisiae and for identical cells in suspension. Glucose uptake and ethanol and glycerol production are approximately two times faster in immobilized cells than in suspended cells. Phosphorus‐31 nuclear magnetic resonance (NMR) spectroscopy of fermenting immobilized and suspended cells shows differences in intermediate metabolite levels such as fructose‐1,6 diphosphate, glucose‐6‐phosphate, and 3‐phosphoglycerate and in internal pH. Carbon‐13 NMR shows an increase in polysaccharide production. These data suggest that immobilization has accelerated the rate of glucose transport or of glucose phosphorylation. These effects of immobilization upon cell metabolism are observed in a very short period of time under conditions in which negligible DNA, RNA, or protein synthesis takes place.
Origin of changes in electrical impedance during the growth and fermentation process of yeast in batch culture
Authors: Ebina Y. , Ekida M. , Hashimoto H. 
Published: December 2004

AbstractThe electrical impedance of the culture medium shows complex changes during the growth and fermentation process of yeast, and this prevents its possible application for the monitoring of certain yeast activities. Clarification of the mechanism of such changes is thus essential for practical use. As a first step toward this aim, the impedance, yeast concentration, and pH of a batch culture medium were measured using special cells with two compartments and also the usual type of cell with one compartment. In the special cells, the yeast was cultured in one compartment only. Conducting ions and nonconducting substances diffused through an intermediate porous membrane sandwiched between the two compartments. The impedances of the two compartments were measured simultaneously by the four‐electrode method. The main mechanism responsible for increasing the impedance was the conducting ions produced by the yeast extract added as a nutrient to the culture broth by certain nonconducting substances during the process of growth. The increase in the yeast concentration was also a minor factor increasing the impedance. These increases surpassed the impedance decrease caused by the increase of H+ ions produced by some accumulated acidic substances, and the impedance thus increased.
Regulation of mammalian cell growth by autocrine growth factors: Analysis of consequences for inoculum cell density effects
Authors: Lauffenburger D. , Cozens C. 
Published: December 2004

AbstractEffects of inoculum cell density on mammalian cell growth in culture have been observed in a variety of experimental systems. Although these effects have been attributed generally to medium conditioning by the cells, there has previously been no quantitative theory proposed for this phenomenon based on developments in molecular and cell biology. In this article, we offer such a theory founded on the regulatory action of autocrine growth factors. A particularly relevant example of these is platelet‐ derived growth factor (PDGF), which is produced by fibroblastic cells in response to stimulation by transforming growth factor β (TGFβ), a common serum constituent, and provides a mitogenic signal for the same cells. A simple mathematical model for the production, diffusive transport, and binding of autocrine growth factors to cell surface receptors, coupled to a model for the dependence of cell proliferation on growth factor receptor binding allows prediction of initial cell population growth rate as a function of inoculum cell density. We focus on situations involving anchorage‐dependent cell growth, in which the cells are attached to a surface. A number of clear results are obtained, most notably the following: 1) for cells cultured on spherical microcarrier bead surfaces, the inoculum cell density needed to produce a given growth rate is linearly proportional to the bead radius; and 2) all other factors being equal, the inoculum cell density on a unit surface area basis needed to produce a given growth rate is greater for spherical microcarrier surfaces than for flat culture dish surfaces. These two results are consistent with the experimental observations of Hu and coworkers1,2 for fibroblast growth in minimal medium plus serum. The model also allows elucidation of the influence of other system parameters, both biological and physical, on initial cell proliferation rate and the inoculum cell density dependence.
Reactive extraction of penicillin G from mycel‐containing broth in a countercurrent extraction decanter
Authors: Likidis Z. , Schlichting E. , Bischoff L. , Schügerl K. 
Published: December 2004

AbstractPenicillin was recovered from mycel‐containing fermentation broth by direct reactive extraction into a counter‐current extraction decanter, Type CA 226–290 of the Westfalia Separator Co., at room temperature via steady state operation. Penicillin concentrations in the feed varied from 3 to 41 g L−1, Amberlite LA‐2 carrier concentrations from 7 to 20 g L−1and/or DITDA carrier concentrations from 7.2 to 84 g L−1, the LA‐2‐to‐penicillin mole concentration ratio from 4 to 6.4, and/or the DITDA‐to‐penicillin mole concentration ratio was maintained at 2. The throughputs of the fermentation broth (520 to 880 L h−1) of the solvent phase (200 to 860 L h−1) and the over all throughput (800 to 1750 L h−1) were high. Extraction degrees of 72 to 96% were achieved between pH 4.6 and 5.1. Without carriers in the same pH range, extraction degrees of only 17 to 19% were attained. By reducing the pH to 2.3 and in the absence of carriers, the degree of extraction was increased to 61%. However, during the extraction, 6.5% of the penicillin decomposed. At these high throughputs, the steady state was attained within 1 to 4 min. Through the mechanical stress, the length of the hyphae was reduced and the protein content of the broth was increased by 50 to 100%. However, this protein content had no appreciable influence on the phase separation.
Media and environmental effects on phenolics production from tobacco cell cultures
Authors: Schmidt Andrew J. , Lee James M. , An Gynheung 
Published: December 2004

AbstractThe effects of various factors in culture medium on the phenolics production from cultured tobacco cells (free and immobilized) were studied. It was found that removing the growth hormone from the medium increased the productivities of phenolics for both free and immobilized cultures. Low initial sucrose concentration in the medium restricted growth and resulted in high cellular productivities of the phenolics for freely suspended cells, but not for the immobilized cells. Addition of 1.4% DMSO to standard culture medium greatly increased phenolics productivities without affecting cell viability in both free and immobilized cell cultures. Continuous operation of a packed‐column reactor of the immobilized cells was achieved for 500 hours. Aeration was accomplished by diffusing pure oxygen through silicone tubing placed inside the reactor. It was found that prolonged cell viability was contingent upon initially operating the reactor with total recycle for several days, and then introducing fresh feed while maintaining a high recycle rate. Immobilized cells packed in a continuous column reactor achieved productivities more than twice that achieved in any batch run.
Analysis of a framework using material balances in metabolic pathways to elucidate cellular metabolism
Authors: Niranjan S. C. , San Ka‐Yiu 
Published: December 2004

AbstractA framework using material balances in metabolic pathways to study cellular metabolism is examined and the results are discussed. Rate measurements on extracellular compounds alone were found to be not always sufficient to validate proposed unique intracellular mechanisms. The conditions to delineate among candidate mechanisms based solely on extracellular measurements are established. The number of half reactions comprising the reaction network is found to be an important parameter.
Biotransformation of benzaldehyde by Saccharomyces cerevisiae: Characterization of the fermentation and toxicity effects of substrates and products
Authors: Long A. , Ward O. P. 
Published: December 2004

AbstractAlthough higher initial rates of phenylacetyl carbinol formation were observed in fermentations containing a high starting benzaldehyde level, a massive reduction in yeast viability was observed resulting in early cessation of production formation. Pulse feeding to maintain lower benzaldehyde concentrations resulted in a lower initial reaction rate, but prolonged yeast viability and the biotransformation. This resulted in higher overall product tilers. As benzaldehyde concentration was increased, yeast growth rate was reduced (0.5 g/L), inhibited (1–2 g/L), or cell viability reduced (3 g/L). Benzaldehyde appeared to alter the cell permeability barrier to substrates and products. Reductions in yeast biomass levels and especially protein and lipid content were observed during the biotransformation. The effects of benzaldehyde and reaction products on yeast pyruvate decarboxylase and alcohol dehydrogenase stability were determined. Homogenized yeast cells produced similar phenylacetyl carbinol levels to whole yeast only if supplemented with thiamine pyrophosphate and magnesium.