bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activity and stability of yeast alcohol dehydrogenase (YADH) entrapped in aerosol OT reverse micelles
Authors: Sarcar Shraboni , Jain Tanoj Kumar , Maitra Amarnath 
Published: December 2004

AbstractThe activity and stability of yeast alcohol dehydrogenase (YADH) entrapped in aerosol OT reverse micellar droplets have been investigated spectrophotometrically. Various physical parameters, e.g., water pool size, w0, pH, and temperature, were optimized for YADH in water/AOT/isooctane reverse micelles. It was found that the enzyme exhibits maximum activity at w0 = 28 and pH 8.1. It was more active in reverse micelles than in aqueous buffers at a particular temperature and was denatured at about 307deg;C in both the systems. At a particular temperature YADH entrapped in reverse micelles was less stable than when it was dissolved in aqueous buffer.
Knowledge‐based control of fermentation processes
Authors: Konstantinov Konstantin B. , Yoshida Toshiomi 
Published: December 2004

AbstractA decade has passed since the first applications of a knowledge‐based approach to the control of bioprocesses were reported. During this period, both the development and application of intelligent control in biotechnology have undergone remarkable evolution in terms of concepts, objectives, and tools. Stimulated by rapid progress in the field of real‐time expert systems, knowledge‐based methodology for the control of fermentation processes has now reached a more mature phase. A growing interest among the biotechnology community and intensive, realistic, and fruitful research being undertaken both in universities and in industry suggest that large‐scale application of knowledge‐based systems for the control of bioprocesses is inevitable. This article provides a concise summary of the main achievements in this new area and discusses recent trends, porblems, and perspectives.
Epoxidation of propene by microbial cells immobilized on inorhanic supports
Authors: Kovalenko G. A. , Sokolovskii V. D. 
Published: December 2004

AbstractImmobilization of gas‐utilizing microorganism strains (Mycobacteria, Rhodococcus, methane‐utilizers) on inorganic supports based on alumina, silicates, and carbon was carried out to develop heterogeneous biocatalysts for the biotechnologic processes, including the process of propene epoxidation. Adsorption ability of these microorganisms, biocatalytic properties of resting and immobilized bacterial cells, and effect of immobilization tehniques on biocatalysis were studied. An approach of double immobilization using inorganic materials (supports and gel) was proposed as simple, universal, and available methopd to immobilize bacterial cells, resulting in a higher retention (up to 100%) of cells' enzymatic activity and enhanced stability.
Protein chromatography in neat organic solvents
Authors: Chang Nancy , Klibanov Alexander M. 
Published: December 2004

AbstractPure formamide and ethylene glycol are used instead of water as processing media for protein chromatography. A number of common proteins are freely soluble in these solvents and most do not undergo irrersible inactivation in them. Batch adsorption studies reveal that proteins readily adsorbed to various ion‐exchangers in formamide and ethyline glycol and subsequently can be completely desorbed by adding inorganic salts (LiCl and NH4NO3) to the solvents. The idea of protein separations in formamide and ethylene glycol is illustrated by column chromatography and preparative separation of mixtures of (i) oxidized A and B chains of insulin and (ii) lysozyme and ribonuclease on the anion‐exchanger triethylaminoethycellulose and the cation‐exchanger phosphocellulose, respectively.
Kinetic analysis of hybridoma growth and monoclonal antibody production in semicontinuous culture
Authors: Leno M. , Merten O.‐W. , Hache J. 
Published: December 2004

AbstractHybridoma I.13.17 was grown in semicontinuous culture in an attempt to investigate the steady‐state concentrations of key components of monoclonal antibody (MAb) synthesis (e.g., intracellular MAb, IgG messenger RNAs) at different dilution rates between 0.008 and 0.055 h−1. There was a general trend of increasing steady‐state levels of total cytoplasmic RNA, total cell‐associated MAb or cytoplasmic MAb, DNA synthesis rate, cellular metabolic activity, heavy (H‐) and light (L‐) chain IgG mRNAs with the increase in dilution rates. Increase in the half‐lives of H‐ and L‐chain mRNAs with increase in dilution rates may be sufficient to account for their increasing levels found under the same conditions. The specific growth rate was profoundly affected by the dilution rate, particularly near the lower end of the dilution rate range. Linear relationships were observed between the steady‐state amounts of total cell‐associated MAb and the relative levels of H‐ and L‐chain mRNAs. Material balances on intracellular MAb demonstrated an increasing percentage of antibody not released into the growth medium (e.g., stored within the cell or anchored to the cell membrane) with increasing dilution rate. The MAb production rate per cell decreased significantly with the increase in dilution rates. No correlation was found between the relative levels of H‐ or L‐chain mRNAs and the specific MAb production rate. Possible implications of rate‐limiting steps in MAb synthesis and secretion are discussed.
Mathematical modeling of induced foreign protein production by recombinant bacteria
Authors: Lee Jongdae , Ramirez W. Fred 
Published: December 2004

AbstractA new generalized mathematical model for recombinant bacteria which includes inducer effects on cell growth and foreign protein production is developed. The model equation set was applied to a host‐vector system, Escherichi coli D1210 and plasmid pSD8. Batch experiments were designed and performed in shake flasks to verify the model. A parameter estimation method was developed and proven to be efficient. Although simple, the model can effectively describe the dynamics of the production of foreign protein in recombinant bacteria and can be used for optimization and control studies to maximize foreign protein production.
Hydrolysis of butteroil by immobilized lipase using a hollow‐fiber reactor: Part I. Lipase adsorption studies
Authors: Malcata F. Xavier , Garcia Hugo S. , Hill Charles G. , Amundson Clyde H. 
Published: December 2004

AbstractAdsorption of proteins from a crude preparation containing a lipase from Aspergillus niger on microporous polypropylene hollow fibers was studied at six different temperatures. Langmuir isotherms accurately describe the overall adsorption equilibria. Lipase is selectively adsorbed relative to the other proteins in the crude preparation. Hence, immobilization also provides further purification of the lipase. The predictions of the Langmuir model for the change in the specific activity of lipase upon adsorption are consistent with experimental results. The loading capacity of the hollow fibers decreases and the adsorption constant increases as temperature is increased. This effect is more significant in the case of lipolytic activity than it is for the total amount of adsorbed protein. Small, positive enthalpy changes are associated with the adsorption of lipase on these hydrophobic membranes.
Metabolic activity of CHO fibroblasts in HEMA–MMA microcapsules
Authors: Uludag Hasan , Sefton Michael V. 
Published: December 2004

AbstractChinese hamster ovary (CHO) fibroblast cells were microencapsulated in polyacrylate membranes (HEMA‐MMA: 75% HEMA) via an interfacial precipitation process. The CHO cells were observed to grow in large aggregates, attached to each other instead of to the capsule wall. When CHO cells were encapsulated at high density (4 × 106 cells/mL), the initial metabolic activity in microcapsules, as determined by the MTT assay, correlated with the polymer‐cell extrusion ratio, presumably because of the dependence of encapsulation efficiency on the relative flow rates. However, there was a large variation in the metabolic activity among individual microcapsules throughout the present study. Capsules with low encapsulation efficiency (at a “seeding” density of 4 × 106 cells/mL) exhibited a rapid increase in the metabolic activity during the following week. When CHO cells were encapsulated at low density (4 × 105 cells/mL), there was only a small increase in the metabolic activity. Only a small fraction (∼5%) of the capsules exhibited a high level of metabolic activity and 40% of the capsules exhibited undetectable metabolic activity even after 2 weeks. We conclude that CHO cells, which served as model cells, survive the encapsulation process and retain an active metabolic state once enclosed by the HEMA‐MMA membranes. However, the resultant microcapsules are extremely heterogeneous in the amount of retained metabolic activity.
Determination of total and active immobilized enzyme distribution in porous solid supports
Authors: Scharer Rolf , Hossain Md. M. , Do D. D. 
Published: December 2004

AbstractThe total and active immobilized enzyme (IME) distributions in porous supports are studied both theoretically and experimentally. In order to determine experimentally the enzyme distribution profiles within a single particle, we construct a diffusion cell containing controlled‐pore glass particles such that the cell would mimic a large pellet support. Our purpose is to study the interplay between the diffusion process within the interparticle void space and immobilization process in the controlled‐pore glass particles onto the evolution of the (total and active) enzyme distributions. A mathematical model is developed to describe the interaction of various processes within the diffusion cell. The immobilized enzymes are determined for a system of trypsin and controlled‐pore glass particles. The total amount of enzymes are determined by the amino acid analysis, and the active fraction is obtained by an active‐site titration. The experimentally measured total IME profiles compare very well with that predicted by the model. The determined active enzyme profile is found to be nonuniform one, and it represents about 40% of the total enzyme immobilized in the support particles.
Ion‐exchange and affinity chromatography costs in α‐galactosidase purification
Authors: Porter Jill E. , Ladisch Michael R. 
Published: December 2004

AbstractThe purification of α‐galactosidase from soybean seeds is a five to six‐step procedure consisting of cryoprecipitation, acid precipitation and ammonium sulfate fractionation followed by two or three chromatography steps. The procedures, while not optimized, were carried out in a manner that resulted in 414–515‐fold purification, as reported previously. The costs of two purification sequences were compared. In the best case, the preparative‐scale costs of stationary phase, reagents, and hardware were $790 per million enzyme units, excluding labor. Stationary phase costs predominated over extraction, chromatography reagent, and eluent costs when the stationary phase is replaced after 10–40 cycles of use. However, if stationary phase life exceeds 50–200 cycles, stationary phase costs become similar in magnitude to eluent and reagent costs. Labor costs, which are process‐specific and difficult to estimate, exceed all other costs by a factor of 10–50 at a small scale of operation and constitute a major cost, regardless of scale. This case study provides equations and a frame‐work for carrying out a first comparison of costs for multistep purification sequences. Column life, throughput, and scale of operation were found to determine not only the magnitude, but also the relative contributions, of the different components that make up purification costs. This analysis shows that there are major opportunities for reducing purification costs through the development of less expensive stationary phases and the implementation of intelligent process control and automation for process scale chromatography.
Irreversible enzyme‐shuttle immunoassay
Authors: Paek Se‐Hwan , Schramm Willfried 
Published: December 2004

AbstractThe concept of a competitive enzyme immunoassay that utilizes simultaneously the bound and the free analyte‐enzyme conjugate (heterobifunctional conjugate) for signal generation in response to varying analyte concentrations in samples has been investigated. Two antigenic sites of the heterobifunctional conjugate are used in the assay for binding to immunoglobulins: the analyte derivative binds to an immobilized antibody, Ab1, and the enzyme component binds to a spatially separated immobilized antibody, Ab2. The analytical system is set up such that in the absence of analyte, the conjugate is predominantly bound in the compartment that contains Ab1. With increasing concentration of native analyte in samples, an increasing concentration of native analyte in samples, an increasing amount of conjugate migrates to the second compartment that contains Ab2. The enzyme bound in each compartment is used for signal generation. Mathematical models have been developed to determine the optimal conditions and to predict the performance of such dual‐antibody systems. The theoretical predictions are supported by experimental results. The dual‐antibody system has been compared with a conventional competitive enzyme immunoassay using the same reagents.
Characterization of mixing in shaker table containers
Authors: Gardner Jeannie , Tatterson Gary 
Published: December 2004

AbstractMixing in shaker table beakers is studied using dye dispersion to measure mixing times. Experimental conditions range from the laminar regime into the turbulent mixing. Different flow patterns occurring in the beakers are reported for the mixing. The transition Reynolds number is determined. Rotational speed of the table, volume of material to be mixed, and viscosity of the material are studied as to their effects on mixing time. A graphical mixing time correlation is provided which is useful for the translation of mixing from laboratory scale to pilot scale.
Cellulase production in continuous culture by Trichoderma reesei on xylose‐based media
Authors: Schafner D. W. , Toledo R. T. 
Published: December 2004

AbstractTrichoderma reesei (QM 9414) produced cellulase in continuous culture, on media containing xylose (1%) supplemented with sorbose (0.3%) to induce cellulase production. Maximum cell mass of 4.54 kg/m3 occurred at pH 4.0 and a dilution rate of 0.0391 h−1 where residual substrate was 0.43 kg/m3, but no cellulase was produced. Maximum cellulase production of 0.69 FPU occurred at pH 3.5 and a dilution rate of 0.0110 h−1, where cell mass production was 2.56 kg/m3 and residual substrate was 0.15 kg/m3. Monod kinetic constants, corrected for endogenous metabolism, were 0.091 h−1, 0.469 kg/m3, 0.00923 h−1, and 0.470 kg cells/kg xylose at pH 3.5, for the maximum specific growth rate, Michaelis–Menten coefficient, endogenous metabolism coefficient, and yield coefficient, respectively. Specific growth rate fitted a maturation time model, which predicted decreasing maturation time with increasing pH.
Effect of serum concentration on hybridoma viable cell density and production of monoclonal antibodies in cstrs and on shear sensitivity in air‐lift loop reactors
Authors: Martens D. E. , Beuvery E. C. , De Gooijer C. D. , Tramper J. 
Published: December 2004

AbstractThe death rate of hybridoma cells, grown in a continuous culture, has been studied in a small air‐lift loop reactor as a function of reactor height and injected gas flow rate. The first‐order death‐rate constant was found to be proportional to the reciprocal height and to the gas flow rate, in accordance with the hypothetical killing volume model for insect cells in bubble columns. Furthermore, the effect of the serum concentration on viable cell concentration and cell productivity has been investigated in a continuous culture. A serum component became growth limiting when the serum concentration was decreased from 2% to 1%. No effect of the serum concentration on specific cell productivity could be measured. Samples from this culture were also studied in the air‐lift loop reactor to determine the effect of serum concentration on the shear sensitivity. The cells' shear sensitivity increased with decreasing serum concentration. The protective effect of serum was found to be physical as well as physiological.
Quantification of the intragranular porosity formed in bioleaching of pyrite by Thiobacillus ferroxidans
Authors: Mustin C. , de Donato Ph. , Berthelin J. 
Published: December 2004

AbstractDuring the bacterial oxidation of a pure pyrite by Thiobacillus ferrooxidans, a great number of corrosion tunnels appear that are easily revealed by scanning electron microscopy observations. This involves an increase in the surface area without significant granulometric reduction of mineral grains. Thus, the evaluation of intragranular porosity, determined by elution front analysis, allows one to estimate accurately the fraction of oxidized sulphide, because of the development of deep holes (propagating pore mechanism). After 60 days of bioleaching, the intragranular porosity represents about 34% of the initial sulphide volume, which corresponds to 25 km of tunnels (2 μm i.d.) per gram of pyrite. On other hand, the granulometric reduction (≈7%) is responsible for a 23% decrease of the initial sulphide volume. The elution front analysis appears as a nondestructive method for measuring the intragranular porosity of the bioleached pyrite.
An experimental study of mass diffusion and reaction rate in an anaerobic biofilm
Authors: Kitsos H. M. , Roberts R. S. , Jones W. J. , Tornabene T. G. 
Published: December 2004

AbstractAn experimental reactor consisting of two chambers, separated by a porous ceramic immobilization matrix, was constructed to measure the effective diffusivity of different compounds and the consumption rates of acetate in developing biofilms. In initial experiments, effective diffusivities for acetate, propionate, isopropanol, and lithium salt through the ceramic immobilization matrix in the absence of biofilm were determined to be 40% to 50% less than in water at infinite dilution. The effective diffusivity of the lithium salt was similar to that of acetate. The effective diffusivity of the lithium salt through biofilms of thickness in the range of 200 to 1200 μm was essentially constant with a value of approximately 7% of that in water at infinite dilution. Acetate consumption in the biofilm was linearly proportional to biofilm thickness up to a biofilm depth of 800 μm. Deviation from linearity appeared in biofilm thicknesses greater than 800 μm. Results of these experiments support previous reports that immobilized cell reactors have significantly higher bioconversion rates than suspended cell systems.
Effect of hydration on the morphology of enzyme powder
Authors: Roziewski Kristin , Russell Alan J. 
Published: December 2004

AbstractWe report the first direct images of the hydration of protein powders. Using an environmental scanning electron microscope (ESEM) we have taken a series of micrographs of a region of the enzyme (subtilisin) power whilst hydrating the sample. In addition, the sample has been viewed during exposure to toluene vapors. The ESEM is a remarkable new instrument that will have wide applicability in imaging of biological materials in their native environments.
Hybridoma perfusion systems: A comparison study
Authors: de la Broise Denis , Noiseux Manon , Massie Bernard , Lemieux Réal 
Published: December 2004

AbstractThe efficiency of lgM production by hybridoma cells (1) cultured in suspension; (2) entrapped in alginate beads; or (3) packed in hollowfiber cartridge bioreactors, were compared in long‐term perfusion cultures. The results showed that steady‐state cell concentration and antibody production, per liter of perfused medium per day, were similar when cells were either entrapped in alginate beads of maintained in suspension. These values were also similar whether cells were maintained at high density in a hollowfiber cartridge bioreactro, or at low density in suspension. This work points out that cell behavior and antibody yield are comparable overall in the various perfusion systems currently used. However, a significant reduction of antibody production appeared whenever a part of the viable cells was lost in the filtrate. The reduction was due both to a decrease of viable cell yield and a decline of lgM productivity on a percell basis. This result is well in agreement with the previously presented model of “grow or die” cell cycle system of hybridoma, which proposes that the ratio of arrested to proliferating cells in perfusion cultures, should be increased in proportion to cell retention in the bioreactor, with a concomitant increase of lgM productivity.
Dye‐ligand membranes as selective adsorbents for rapid purification of enzymes: A case study
Authors: Champluvier B. , Kula M.‐R. 
Published: December 2004

AbstractA new adsorbent for the selective binding of enzymes, in the form of microporous membranes carrying triazine dyes as pseudo‐affinity ligand, has been implemented in the recovery of glucose‐6‐phosphate dehydrogenase from yeast. A detailed investigation of the process parameters has been performed. In the adsorption step, the contact time for binding G6PDH could be reduced down to 0.25 s without significant decrease of the capture efficiency. Hence, fast filtration allowed to isolate G6PDH from a dilute extract (1.6 μg G6PDH · mL−1), where the enzyme accounted for 1% of the proteins. The yield of the selective elution step using NADP was only 70% at best. It could be improved to near 100% by supplementing the eluent with ethylene glycol, without loss of selectivity. A Scale‐up of the cross‐section of the membrane by a factor of 40 allowed to purify 1140 U from 0.6 L extract from 1% to 57% purity with 82% yield, within 10 minutes. The case study presented here demonstrates the applicability of general‐purpose membrane adsorbents for the purification of enzymes.
Recovery of canola meal proteins by precipitation
Authors: Chen M. , Rohani S. 
Published: December 2004

AbstractRecovery of rapeseed proteins from defatted canola meal by precipitation was investigated. The ability of different precipitating agents, such as sodium hexametaphosphate (HMP), carboxymethylcellulose (CMC), ammonium sulphate, and isoelectric precipitation using HCl, were evaluated based on the yield and mean size of protein aggregates. Almost 94% of dissolved protein was precipitated in the presence of 2.7M ammonium sulphate, while the largest mean protein particle size (32 μm) was obtained in the presence of HMP at pH 3.3.