bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new immobilized cell system with protection against toxic solvents
Authors: Tanaka Hideo , Harada Satoru , Kurosawa Hiroshi , Yajima Mizuo 
Published: December 2004

AbstractA new immobilized cell system providing protection against toxic solvents was investigated so that normal fermentations could be carried out in a medium containing toxic solvents. The system consists of immobilized growing cells in Ca‐alginate gel beads to which vegetable oils, which are inexpensive absorbents of solvents, had been added. The ethanol fermentation of Saccharomyces cerevisiae ATCC 26603 was used as a model fermentation to study the protection afforded by the system against solvent toxicities. The fermentation was inhibited by solvents such as 2‐octanol, benzene, toluene, and phenol. Ethanol production of one batch was not finished even after 35 h using immobilized growing yeast cells in conventional Ca‐alginate gel beads in an ethanol production medium (5% glucose) containing 0.1% 2‐octanol, which is used as a solvent for liquid‐liquid extraction and is one of the most toxic solvents in our experiments. With the new immobilized growing cell system using vegetable oils, however, four repeated batch fermentations were completed in 35 h. Castor oil provided even more protection than soy bean, olive, and tung oils, and it was possible to complete six repeated batches in 35 h. The immobilized cell system with vegetable oils also provided protection against other toxic solvents such as benzene and toluene. A possible mechanism for the protective function of the new immobilized cell system is discussed.
Immobilization of activated sludge by PVA–boric acid method
Authors: Hashimoto Susumu , Furukawa Kenji 
Published: December 2004

AbstractA new method (polyvinyl alcohol–boric acid method) for an inexpensive and effective immobilization of activated sludge was developed. Using activated sludge immobilized by this PVA–boric acid method, synthetic waste‐water was treated at a high loading rate of 0.5–2.35 kg TOC/m3 day. Total organic carbon and total nitrogen were removed at efficiencies of 93 and 30–40%, respectively. The kinetic constants Y and b for this immobilized activated‐sludge process were determined to be 0.594g mixed liquor suspended solids (MLSS)/g TOC and 0.0219 day−1, respectively. The cost calculation of chemicals required for the immobilization of activated sludge by this PVA–boric acid method was proved to be extremely inexpensive for the immobilization of activated sludge.
Inexpensive, rapid procedure for bulk purification of cellulase‐free β‐1,4‐D‐xylanase of high specific activity
Authors: Tan Larry U. L. , Yu Ernest K. C. , Louis‐Seize Gerald W. , Saddler John N. 
Published: December 2004

AbstractA process has been developed for the bulk purification of cellulase‐free β‐1,4‐D‐xylanase from the fungus Trichoderma harzianum E58. The process involved the primary step of ultrafiltering the culture filtrate via a 10,000‐molecular‐weight cut‐off membrane to separate the cellulase (retentate) and xylanase (permeate) fractions. The cellulase component was concentrated by 40‐ to 60‐fold, resulting in an enzyme complex that could effectively hydrolyze high concentrations of cellulose and xylan to glucose and xylose. The xylanase was concentrated and solvent exchanged by adsorption to a cationic exchanger, SP‐ZetaPrep 250, followed by elution with a pH change in the buffer to give a purified and concentrated xylanase complex dissolved in a low‐salt buffer. The resultant xylanase system was pure by the criteria of sodium dodecyl sulfate polyacrylamide electrophoresis, had a very high specific activity of 2400 IU/mg protein, was virtually free of filter paper activity, and had a ratio of contaminating filter paper activity of 2 × 10−6 (0.009% endoglucanase activity). Approximately 3.3 g protein, which contained in excess of 7 × 106 IU xylanase activity, was obtained from 17 L original culture filtrate. The process scheme was designed to facilitate scale‐up to an industrial level of production.
Dynamic analysis of irreversible adsorption of protein on porous polymer resins as studied by pulse injection method
Authors: Nakamura Katsunori , Hirai Youhei , Kitano Hiromi , Ise Norio 
Published: December 2004

AbstractIrreversible adsorption of bovine serum albumin onto porous polymer resins is examined by a pulse injection method. The experimental results are theoretically analyzed by a model based on the assumption that there exist three kinds of binding sites with different binding rates, which are considered to exist in the vicinity of the outer periphery surface, the inner surface of macropore, and the micropore, or center part, of particles. The three kinds of adsorption rates are also evaluated by a batch method and are nearly equal to the corresponding kinetic parameters by this method. The amount of BSA bound irreversibly to the resins is independent of the protein concentration and the flow rate examined, which suggests that protein molecules penetrate into pores of resins and occupy almost all the effective binding sites in the resins. The total amount of bound BSA shows a pH dependence with a maximum near the isoelectric point of BSA, and the amount of BSA bound at the slowest rate is most largely influenced by pH.
Lipase‐catalyzed ester exchange reactions in organic media with controlled humidity
Authors: Goderis H. L. , Ampe G. , Feyten M. P. , Fouwé B. L. , Guffens W. M. , Van Cauwenbergh S. M. , Tobback P. P. 
Published: December 2004

AbstractImmobilized lipase activity is studied in organic solvent systems of controlled water content under the influence of a variety of reaction parameters, such as temperature, relative humidity, substrate concentrations, and type of fatty acid used. Control of the amount of water in the reaction system was found to be a valuable tool for the orientation of the reaction process and for the determination of the final reaction products. The properties of the immobilized lipase were studied using the interesterification of triolein and palmitic acid as the model system.
Gibberellic acid by solid state fermentation: Consistent and improved yields
Authors: Kumar P. K. R. , Lonsane B. K. 
Published: December 2004

AbstractFive strains each of Gibberella fujikuroi and Fusarium monoliforme were screened to select G. fujikuroi P‐3, a strain capable of giving consistent production of gibberellic acid (GA3) by solid state fermentation (SSF). The comparative production of GA3 by SSF and submerged fermentation (SmF) indicated better productivity with the former technique. The accumulation of GA3 was 1.626 times higher in the case of SSF. On the basis of available carbohydrates in the media, the percent conversions were 0.096 and 0.156 in SmF and SSF, respectively. The use of coarse wheat bran of the particle size of 0.3–0.4 cm resulted in an increase of 2.5 times in the yield of GA3. The enrichment of commercial wheat bran with soluble starch gave enhanced accumulation to an extent of 3.5 times. The relation between GA3 production and cell growth in SSF was similar to that encountered in SmF. The consistent and improved yields to a tune of 1.22 g GA3 per kilogram dry moldy bran (DMB) establish the potential and feasibility of SSF for the production of GA3 by G. fujikuroi P‐3. On preliminary cost analysis, a net savings of about 60% and 50% on fermentation medium cost and the expenditure on down‐stream processing, respectively, as compared to the presently employed SmF technique was evident.
Cell cycle analysis of plasmid‐containing Escherichia coli HB101 populations with flow cytometry
Authors: Seo Jin‐Ho , Bailey James E. 
Published: December 2004

AbstractThe relationship between cell mass and cell number dynamics for bacteria such as Escherichia coli depends on the cell cycle parameters C and D. Effects of plasmid copy number on these cell cycle parameters have been studied for Escherichia coli HB101 containing pMB1 plasmids propagated at different copy numbers ranging from 12 to 122. Determination of cell cycle and cell size parameters was accomplished using flow cytometry data on single‐cell light scattering and DNA content frequency functions in conjunction with a mathematical model of cell population statistics. Two independent methods for estimating C and D intervals based on flow cytometry were developed and applied with essentially identical results. The presence of plasmids decreases the C and D periods, mean cell sizes, and initiation masses for chromosome replication by 14, 24, 38, and 18%, respectively, relative to corresponding values for plasmid‐free host cells. Plasmid copy number has a negligible influence on these parameters, suggesting that host‐plasmid inter actions which determine these properties are centered on the single plasmid selected for replication according to the random selection model established for ColE1‐type plasmids.
Reaction rate calculations for cosubstrates diffusing into catalyst layer from opposite sides
Authors: Karel Steven F. , Robertson Charming R. 
Published: December 2004

AbstractThe effects of diffusion on a reaction taking place in a permeable catalyst are examined theoretically for the case where the reaction has two substrates supplied from opposite sides of a catalytic slab. The solutions of the reaction–diffusion equation for combinations of zeroth‐and first‐order kinetics are given in terms of an effectiveness factor and a parameter describing the position in the layer where the reaction occurs. In these terms, the results vary only weakly with reaction order. The use of the exact solutions for a reaction that is zeroth order in both sub strates is proposed as a general rule for estimating the reaction rate and the reaction position.
Ionic binding of biologically active proteins on cross‐linked acrylic macromolecular supports
Authors: Maxim Steliana , Flondor Aurelia , Carpov Adrian 
Published: December 2004

AbstractThe immobilization process of some biologically active proteins on acrylic ion exchange supports was studied. The cross‐linking and swelling coefficient, as well as the molecular weight of the enzyme, were proved to influence the immobilization process. The kinetic data indicate mainly a binding process controlled by diffusion. The uptake coefficient values of different proteins ranged between 35.0 and 98.0%. The laboratory experiments per formed with some of the obtained enzymic preparation certify the preservation of the catalytic activity following the immobilization process.
The modeling and analysis of the elution stage of biospecific adsorption in fixed beds
Authors: Arve B. H. , Liapis A. I. 
Published: December 2004

AbstractA mathematical model that describes the dynamic behavior of the elution stage of biospecific adsorption (affinity chromatography) in a fixed bed is developed and solved. Both non‐selective and selective elution methods are considered. The results show that the duration of the elution stage for a given bed length decreases as the value of the Porath parameter for elution increases. The concentrating effect of the elution stage on the adsorbate of interest increases as the bed length and the value of the Porath parameter for elution increase. It is shown that it is inappropriate to assume that the eluent is infinitely fast distributed within the pores of the particles, and an interesting result involving a local maximum in the effluent concentration of the selective eluent is obtained when the direction of flow in the elution stage is the same as in the adsorption and wash stages and the bed length is large. When the direction of flow during elution is opposite (as compared to being the same) to that employed in the adsorption and wash stages, a shorter total elution time is obtained. The advantage gained with a reversed flow increases as the bed length decreases.
Calorimetric investigation of aerobic fermentations
Authors: Birou Bernard , Marison Ian W. , Stockar Urs Von 
Published: December 2004

AbstractA modified bench scale calorimeter has been employed to determine the heat generated by various microbial strains growing on a range of different substrates, covering degrees of reduction from 3 to 6.13. The results are analyzed, and interpreted in the light of coupled enthalpy and elemental balances. The heat released by the microbial cultures has been found to correlate linearly with other process variables, such as biomass generation and oxygen uptake. The ratio between the heat generated and the biomass formed, the so‐called “heat yield” (YQ/x), has been shown both on theoretical and experimental grounds to increase with increasing degree of reduction of the substrate and to decrease with increasing biomass yield. The two effects could be combined into a simple model which permits the amount of heat released per unit of biomass formed to be predicted from the degree of reduction of the substrate as the only independent variable. The ratio between the heat generated and the oxygen taken up was constant at 440 kJ (mol O2)−1 throughout all experiments as expected from theoretical considerations for strongly aerobic processes.
Noninferior periodic operation of the metabolite producing biological reactor
Authors: Hasegawa Sachiyuki , Matsubara Masakazu , Shimizu Kazuyuki 
Published: December 2004

AbstractThe optimal periodic operation of the biological reactor in which the metabolites belonging to Type I or II in Gaden's classification are produced was investigated from the viewpoint of the multiobjective programming problem. In addition to the productivity of the desired product, its concentration and the conversion of the substrate which have a large influence on the performance of the separation process following the fermentation process were adopted as the objective functions. The growth of cells was assumed to be inhibited both by the substrate and the product, and the Luedeking‐Piret model was employed for the specific production rate. The optimal periodic operation was determined by use of the optimization method due to Miele. It was clarified that the noninferior set for the periodic operation was generally composed of the repeated batch portion and the repeated fed‐batch one.
Single‐step unimolecular non‐first‐order enzyme deactivation kinetics
Authors: Sadana Ajit , Henley James P. 
Published: December 2004

AbstractA two‐parameter deactivation model is proposed to describe the kinetics of activity stabilization for some enzymes. The single‐step unimolecular mechanism exhibits non‐first‐order deactivation kinetics since the final enzyme state, E1 is not completely inactivated. The usefulness of the model is demonstrated by applying it to the inactivation of different enzymes. The influence of the concentration of active ester, ionic strength, and pH on the model parameters is examined during the inactivation of electric eel acetylcholinesterase.25 In general, inactivators would decrease the level of activity stabilization, α1, and increase the first‐order inactivation rate constant, k1. The effect of protecting agents would be to increase α1 and to decrease k1.
Quantification of the degree of acclimation of a mixed culture to an industrial landfill leachate
Authors: Evans Patrick J. , Ahlert Robert C. 
Published: December 2004

AbstractQuantification of the degree of acclimation of a mixed culture is demonstrated. An industrial landfill leachate was used as a model mixed substrate. The biodegradable fraction, the specific rate of substrate uptake, and the apparent reaction order were measured. The method of acclimation did not appear to affect the biodegradable fraction. The apparent reaction order is shown to be related to the difference between the rates of uptake of the various leachate components. This difference is defined as the differential in the rate. The effects of a supple mental carbon source and different inocula were investigated. Addition of glucose tends to diminish the differential but also decreases the specific rate of substrate uptake. The outcome of an acclimation procedure is dependent on the quality of the inoculum; however, a poor inoculum does not preclude an acclimation that yields a superior culture. A normalized rate coefficient is shown to have merit as an indicator of the degree of acclimation. Two microorganisms were isolated, Acinetobacter calcoaceticus var. Iwoffi and Moraxella sp., that could grow axenically with the leachate as their sole source of carbon. Comparisons are made between pure and mixed cultures with regard to biodegradable fraction, specific rate of substrate uptake, and apparent reaction order.
Enzymatic synthesis of L‐cysteine
Authors: Hsiao Humg‐Yu , Wei Tena 
Published: December 2004

AbstractO‐Acetylserine sulfhydrase in the form of a crude extract from Salmonella typhimurium LT2 was used for the production of L‐cysteine from L‐O‐acetylserine and sodium hydrosulfide at pH 7.0 and 25°C. The two substrates have quite different pH stability relationships. O‐Acetylserine readily rearranges to N‐acetylserine and the rate of this O → N acyl transfer reaction increases at higher pH, temperature, and concentration of O‐acetylserine. On the other hand, sodium hydrosulfide is more soluble at a higher pH. A stirred‐tank bioreactor with a continuous substrate feed was employed to overcome this problem. The O‐acetylserine feed was stored at its saturation level (2.05M) at pH 5.0, and the sodium hydrosulfide feed was dissolved at 2.05–2.3M without pH adjustment (pH ≥ 11.5). Both substrates were simultaneously introduced into the bioreactor. The performance of the bioreactor was optimized by employing an automatic feedback control system to regulate the concentration of O‐acetylserine in the bioreactor. This feedback control system was based on the fact that as the bioconversion proceeds, protons are produced along with cysteine. A pH controller thus detected the decrease in pH and activated the substrate pumps. After mixing in the bioreactor, these two substrate solutions behaved as a base due to the high alkalinity of sodium hydrosulfide. Thus, substrate infusion started when the pH was lower than the set point, i.e., the reaction pH, and stopped when the pH was raised higher than the set point. The amount of substrate introduced was determined by the alkalinity of the mixture of the two substrates, which in turn was controlled by the concentration of sodium hydrosulfide. After optimizing the sodium hydrosulfide concentration and the substrate feed rate, the bioconversion gave a productivity of 3.6 g L‐cysteine/h/g dry cell weight S. typhimurium, an L‐cysteine titer of 83 g/L and a molar yield based on O‐acetylserine of 94%.
Theoretical and experimental studies on the influence of ultrasound on immobilized enzymes
Authors: Schmidt Peter , Rosenfeld Eike , Millner Rudolf , Czerner Regina , Schellenberger Alfred 
Published: December 2004

AbstractExperimental investigations on α‐amylase and glucoamylase bound to porous polystyrene show that the activity of immobilized enzymes can be raised in the presence of an ultrasonic field. The maximum activity increase in a flow cuvette at 7.6 MHz and a sound intensity of 5 kW/m2 amounts to more than 200% under the given experimental conditions. A mathematical model based on the differential equation for the interior and exterior substrate transport is set up and solved numerically. From the theoretical considerations and the experiments it is evident that the mechanism of the ultrasonic effect can be explained in terms of a reduction of the unstirred diffusion layer around the matrix particles.
Modeling dynamic experiments on the anaerobic degradation of molasses wastewater
Authors: Denac M. , Miguel A. , Dunn I. J. 
Published: December 2004

AbstractThe kinetics of anaerobic degradation of a molasses wastewater were measured under constant pH conditions in a laboratory scale packed bed reactor. In continuous and batch experiments the formation and degradation rates of the organic acids (butyric, propionic and acetic) have been followed. The influence of hydrogen gas on the acid degradation rates has been measured and, contrary to the literature and the thermo‐dynamic calculations, no inhibition was detected, biofilm diffusional effects may be the reason. Two dynamic simulation models were tested, a heterogeneous model, which considered the biofilm diffusion–reaction phenomena and a quasihomogeneous model with the same kinetics. Except for hydrogen, the diffusion effects were found to be negligible. Otherwise both models gave essentially the same results and the time profiles of acids, hydrogen, carbon dioxide and methane agreed relatively well with dynamic startup experiments. Batch experiments showed the acid concentrations to be highly sensitive to the initial molasses concentration. This aspect was not included in the model but is being investigated further.
Revised enzyme synthesis rate expression in cybernetic models of bacterial growth
Authors: Turner Brian G. , Ramkrishna Doraiswami 
Published: December 2004

AbstractA revised enzyme synthesis rate expression for cybernetic models of bacterial growth is presented. The rate expression, which is comprised of inducible and constitutive contributions, provides for a basal enzyme level that is necessary to predict certain types of commonly observed continuous culture transients. The response of a continuous culture to a step change in feed stream composition is simulated using both the old and new formulations, and the ramifications for the “matching‐law” formulation are discussed.
Limitation of growth rate by two complementary nutrients: Some elementary but neglected considerations
Authors: Baltzis Basil C. , Fredrickson A. G. 
Published: December 2004

AbstractExperimental data in the literature show that the yield of biomass from a particular nutrient when that nutrient limits growth rate is often significantly different than the yield from the nutrient when some complementary nutrient limits growth rate. This article explores some possible consequences for bioreactor dynamics of dependence of yield coefficients on the identity of the nutrient that limits growth rate.
Theoretical study of tryptophan operon: Application in microbial technology
Authors: Sinha Somdatta 
Published: December 2004

AbstractA model for the tryptophan operon is formulated based on the genetic and biophysical data available on the structure of the operon and the nature of interactions between the represser and its ligands. Studies have been done, on wild‐type, superrepressing, and loose‐binding strains to identify conditions at which the stability of the system changes (i.e., evolves to a stable synthesis or periodic synthesis with increasing amplitude). Also, the factors that increase the yield of tryptophan are studied and predictions made, based on the results, for obtaining overproducing strains of tryptophan that can be used for the industrial production of this useful amino acid.
Effect of pH on growth of mixed cultures in batch reactor
Authors: Lallai A. , Mura G. , Miliddi R. , Mastinu C. 
Published: December 2004

AbstractThis work has studied the effect of pH on specific growth rate μ, yield factor Y, and specific substrate consumption rate U for two mixed microbial populations (sludge A and B) in a batch reactor with a limiting substrate (phenol). The mathematical analysis of μ and U as a function of pH has been applied not only to the results of the present work but also to other published data. On the basis of the results obtained, the following remarks can be made: (a) The effect of pH on bacterial activity differed for the two sludges; (b) variations in pH of one unit more or less than optimum pH can give rise to appreciable variations in μ and U; and (c) with regard to the mixed populations used in this study, the μ or U and pH data for the range investigated can be suitably described by a parabolic relation.