bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of hydraulic regime on organic polymer uptake in the activated sludge process
Authors: Maxham John V. , Maier Walter J. 
Published: December 2004

AbstractMathematical models presented in a previous paper (Biotechnol. Bioeng., 20, 865 (1978)) describing unsteady‐state bacterial growth on organic polymers are modified to predict the holding time necessary to attain a given treatment level in a steady‐state activated sludge process. Various hydraulic regimes for the activated sludge aeration basin are assumed, and it shown that the hydraulic regime strongly influences the total holding time necessary to attain a given treatment objective. Maintaining the highest possible concentrations of bacteria, extracelluar enzyme, cleavable polymer bond, and utilizable oligomer in the aeration basin during the course of treatment yields the highest possible organic nutrient uptake. However, it is shown that aeration‐basin hydraulic regimes that maintain relatively high levels of bacteria and extracellular enzyme also maintain relatively low levels of polymer bond and utilizable oligomer and vice versa. Thus the efficacy of a particular aeration‐basin hydraulic regime depends on its ability to maintain at high levels those concentrations that most strongly influence the kinetics of enzymatic hydrolysis or utilizable oligomer uptake.
Modeling cell concentration in complex media
Authors: Alford J. S. 
Published: December 2004

AbstractA model that continuously predicts the concentration of microorganisms in complex medium fermentations is suggested. The model uses carbon dioxide evolution as its primary input and assumes that respiration activity can be differentiated into growth‐related and maintenance‐related functions. This model can be programmed on computer‐coupled vessels and used to standardize on a physiological fermentation inoculum transfer time. The cell concentration estimate can also be used to calculate specific growth rate and can be combined with additional monitored information to calculate other important fermentation parameters such as specific oxygen uptake.
Laboratory‐scale production of acetoin plus diacetyl by Enterobacter cloacae ATCC 27613
Authors: Gupta K. G. , Yadav N. K. , Dhawan S. 
Published: December 2004

AbstractConditions for the laboratory‐scale production of acetoin plus diacetyl by Enterobacter Cloacae ATCC 27613 were studied. Thirty‐five g acetoin plus diacetyl/50 g sucrose were obtained when fermentation was carried out in 2. 5 liter medium containing 12.5 g peptone and 12. 5 g yeast extract, at pH 7.0, in a 5 liter conical flask on a shaker (240rpm) at 28–30°C for 48 hr. Recovery of pure diacetyl was 85% of the total plus diacetyl.
Influence of manufacturing variables on the characteristics and effectiveness of chitosan products. III. Coagulation of cheese whey solids
Authors: Wu A. C. M. , Bough W. A. , Holmes M. R. , Perkins B. E. 
Published: December 2004

AbstractTen chitosan products, prepared as described in part I of this study, were evaluated in jar tests that measured their effectiveness for coagulation of suspended solids and removing turbidity from cheese whey. A polynominal regression analysis was found to be useful for determining the optimal effectiveness of each chistosan preparation, and was expressed as the percent reduction on turbidity per unit concentration of chitosan added. The effectiveness of the chitosan products was found to be inversely related to their molecular‐weight values. This situation was different from the findings described in part II of this study, in which the filterability of activated sludge was tested. Enzymatic deproteination yielded chitosan products that performed better than those produced by alkali deproteination. Demineralized products were also more effective than those that had not been demineralized. The preparations deacetylated under a nitrogen atmosphere were more effective than those deacetylated in air, but this was shown to be true only for the first 5 min of deacetylation. When deacetylated for 15 min, no differences were noted. In this study, differences in performance between the various products were largely due to the differing dosages required to achieve the maximum reduction in turbidity of cheese whey, while the maximum responses achieved by the various products tested were about the same. A commercial product, which was less effective as a sludge coagulating agent in part II of this study, was more effective for cheese whey coagulation and turbidity removal than the majority of the experimental chitosan preparations tested.
Human interferon production with diploid fibroblast cells grown on microcarriers
Authors: Giard Donald J. , Loeb David H. , Thilly W. G. , Wang D. I. C. , Levine D. W. 
Published: December 2004

AbstractA variety of diploid human fibroblast lines have been successfully grown to high densities (>106 cell/ml) on recently developed microcarriers. Interferon induction using poly I·poly C and a superinduction procedure resulted in yields greater than 10,000 units/ml with one cell line. A direct comparison of microcarrier cultures to roller bottle cultures showed equivalent interferon yields on a per cell basis and some apparent differences relating to optimum inducer concentrations and kinetics of interferon accumulation.
Kinetics and stability of immobilized chicken liver xanthine dehydrogenase
Authors: Tramper Johannes , Angelino Steven A. G. F. , Müller Franz , van der Plas Henk C. 
Published: December 2004

AbstractXanthine dehydrogenase (EC 1.2, 1.37) was isolated from chicken livers and immobilized by adsorption to a Sepharose derivative, prepared by reaction of n‐octy‐lamine with CNBr‐activated Sepharose 4B. Using a crude preparation of enzyme for immobilization it was observed that relatively more activity was adsorbed that protein, but the yield of immobilized activity increased as a purer enzyme preparation was used. As more activity and protein were bound, relatively less immobilized activity was recovered. This effect was probably due to blocking of active xanthine dehydrogenase by protein impurities. The kinetics of free and immobilized xanthine dehydrogenase were studied in the pH range 7.5–9.1. The Km and V values estimated for free xanthine dehydrogenase increase as the pH increases; the K'm and V values for the immobilized enzyme go through a minimum at pH 8.1. By varying the amount of enzyme activity bound per unit volume of gel, it was shown that K'm is larger than Km as result of substrate diffusion limitation in the pores of the support material. Both free and immobilized xanthine dehydrogenase showed substrate activation at low concentrations (up to 2μM xanthine). Immobilized xanthine dehydrogenase was more stable than the free enzyme during storage in the temperature range of 4−50°C. The operational stability of immobilized xanthine dehydrogenase at 30°C was two orders of magnitude smaller than the storage stability. t½ was 9 and 800 hr, respectively. The operational stability was, however, better than that of immobilized milk xanthine oxidase (t½ = 1 hr). In addition, the amount of product formed per unit initial activity in one half‐life, was higher for immobilized xanthine dehydrogenase than for immobilized xanthine oxidase. Unless immobilized milk xanthine oxidase can be considerable stabilized, immobilized chicken liver xanthine dehydrogenase is more promising for application in organic synthesis.
Data consistency, yield, maintenance, and hysteresis in batch cultures of Candida lipolytica cultured on n‐hexadecane
Authors: Ferrer Alexies , Erickson L. E. 
Published: December 2004

AbstractCandida lipolytica was cultured batchwise using n‐hexadecane as the main carbon source. Biomass production, n‐hexadecane consumption, oxygen consumption, and carbon dioxide evolution were measured to follow the fermentation. The consistency of the measured data was examined using integrated and instantaneous available electron and carbon balances. Values of the “true” growth yield, ηmax, and maintenance coefficient, me were estimated using three different sets of data (biomass and n‐hexadecane, oxygen and biomass, and CO2 and biomass), and the results were compared with estimates obtained from literature data. Hysteresis patterns were observed in plots of specific rates of oxygen consumption and carbon dioxide evolution versus specific growth rate.
Saccharification of cellolulose by the cellulolytic enzyme system of Thermonospora sp. I. Stability of cellulolytic activities with respect to time, temperature, and pH
Authors: Hägerdal Bärbel , Ferchak John D. , Pye E. Kendall 
Published: December 2004

AbstractThe stabilities and optima with respect to temperature and pH of the β‐glucosidase, Avicelase, and carboxymethylcellulase (CMCase) activity of Thermomonospora sp., in the culture filtrate, culture whole broth, and filtrate after sonication of culture solids, are reported. The β‐glucosidase is cell associated and has an optimal activity at about pH 6.5 and 55°C. In the whole culture broth, it has a half‐life of about 8 hr at 55°C and less than 1 hr at 60°C, while the half‐life of the activity in the sonicated, cell‐free filtrate is less than 1 hr at 55°C. The Avicelase and CMCase activities occur in the extracellular culture fluid and have optima at about pH 7.0 and 5.9, and 65 and 70°C, respectively. The CMCase activity is stable over 24 hr at 60°C, but declines by 50% in the same period at 65°C. The Avicelase activity declines by 15% over 24 hr at 55°C, and by 50% at 60°C. The highest pH studied (pH 7.3) was the most destabilizing for all three activities. The thermostable characteristics of the cellulases from Themomonospora appear to make them suitable for commercial saccharification processes operating at elevated temperatures.
The monod equation: A revisit and a generalization to product inhibition situations
Authors: Levenspiel Octave 
Published: December 2004

AbstractThis paper shows how to treat the substrate‐limiting Monod equation in a straight forward manner for different types of fermentors (plug‐flow, batch, and mixed‐flow) using the general language of chemical reaction engineering. Straight‐line plots are developed for directly finding the kinetic constants of the equation, and an example using Monod's original data illustrates the procedure. The Monod equation is then generalized to account for the effects of both substrate and inhibitory toxic wastes. Finally, for pure product inhibition performance, expressions are derived for various reactor types, and correlation graphs are developed for finding the kinetic constants of the reaction. An example from the recent literature shows that this equation form fits the data extremely well.
Kinetics of biphasic growth of yeast in continuous and fed‐batch cultures
Authors: Toda K. , Yabe I. , Yamagata T. 
Published: December 2004

AbstractThe influence of dilution rate on the production of biomass, ethanol, and invertase in an aerobic culture of Saccharomyces carlsbergensis was studied in a glucose‐limited chemostat culture. A kinetic model was developed to analyze the biphasic growth of yeast on both the glucose remaining and the ethanol produced in the culture. The model assumes a double effect where glucose regulates the flux of glucose catabolism (respiration and aerobic fermentation) and the ethanol utilization in yeast cells. The model could successfully demonstrate the experimental results of a chemostat culture featuring the monotonic decrease of biomass concentration with an increase of dilution rate higher than 0.2 hr−1 as well as the maximum ethanol concentration at a particular dilution rate around 0.5 hr−1. Some supplementary data were collected from an ethanol‐limited aerobic chemostat culture and a glucose‐limited anaerobic chemostat culture to use in the model calculation. Some parametric constants of cell growth, ethanol production, and invertase formation were determined in batch cultures under aerobic and anaerobic states as summarized in a table in comparison with the chemostat data. Using the constants, a prediction of the optimal control of a glucose fed‐batch yeast culture was conducted in connection with an experiment for harvesting a high yield of yeast cells with high invertase activity.
Production of high‐fructose syrup by a heat‐fixed Lactobacillus sp.
Authors: Bhatia Mamta , Prabhu K. A. 
Published: December 2004

AbstractA Lactobacillus sp. isolated from soil and capable of growing on xylose‐containing medium exhibited high glucose isomerase activity. The enzyme was thermostable, stable toward dialysis, and activated by heat treatment. It did not show the presence of xylose or ribose isomerase activities; the Km for glucose and xylose substrates were 0.48M and 0.513M, respectively. The heat treatment of ultrasonic crude extract gave insoluble fixed active glucose isomerase enzyme. The properties of free and immobilized enzyme in heat‐fixed whole cells differed in many respects. The optimum temperature for enzyme activity changed from 70 to 85°C, the optimum substrate concentration changed from 1.0M to 2.4M, and the optimum pH from 7.4 to 6.0. Co2+ and Mg2+ ions activated the enzyme when used singly, but in combination they inhibited the enzyme and Mn2+ had no effect on the enzyme. Free and immobilized enzymes, when used in the used in the conversions of corn and bagasse hydrolysates to fructose, gave 58, 25.6%, and 50, 27.6% conversions, respectively. Immobilized enzyme retained a significant activity for more than 30 hr and was able to operate at higher glucose concentrations showing less products inhibition effect as compared to free enzyme. In the batch process it was able to operate for about eight cycles.
Dynamics of commensalistic systems with self‐ and cross‐inhibition
Authors: Sheintuch M. 
Published: December 2004

AbstractUp to three stable steady states are possible in a simple commensalistic system, taking place in an open‐loop mixed reactor when the growth rates of the two species are inhibited by the substrates they prey on (Self‐inhibition). Two stable states are possible in a system with noncompetitive inhibition of the species by the substrate they are not preying on (cross‐inhibition). A large number of steady states as well as oscillatory states are possible when both self‐ and cross‐inhibition are strong. Multiplicity of steady states is also possible in a reactor with biomas recirculation for these kinetics. Yet, the latter is more stable than the open‐loop reactor in the sense that the domain of steady‐state multiplicity is narrower. The stability of steady states and the dynamics of the systems for each of the investigated kinetics are summarized in a qualitative phase plane. The importance of the analysis for improving the selectively and yield of the system and for predicting the response of the system to changes in the operating conditions, is discussed.
Immobilization of proteins by reductive alkylation with hydrophobic aldehydes
Authors: Wu Hua‐Lin , Means Gary E. 
Published: December 2004

AbstractA new method is described for the immobilization of enzymes and other proteins onto hydrophobic gels. Trypsin, for example, can be quantitatively immobilized by reaction with sodium cyanoborohydride and dodecyladehyde‐coated Octyl‐Sepharose. Noncovalent interactions between the hydrophobic gel and approximately 10 resulting dodecylamino groups in the modified enzyme bind it very strongly but do not affect its ability to hydrolyze benzolarginine ethyl ester. The same procedure can also be used to immobilize E. Coli asparaginase and yeast alcohol dehydrogenase in high yield.
Multilevel control of multistage continuous culture using a microprocessor
Authors: Fawzy A. S. , Hinton O. R. 
Published: December 2004

AbstractThis paper describes the implementation of multilevel techniques using a microprocessor to control multistage continuous culture systems. A system which produces gramicidin S is taken as an example. The single level technique using the conjugate gradient method is applied to solve the two‐stage and the three‐stage continuous culture and is compared with the multilevel one. The results show that the application of multilevel techniques is more advantageous and suitable for this system than any other method which has been utilized so far. The advantages of using a microprocessor will be stated.
Fermentation pattern of sucrose to ethanol conversions by Zymomonas mobilis
Authors: Lyness Ed , Doelle Horst W. 
Published: December 2004

AbstractGeneral patterns of sucrose fermentation by two strains of Zymomonas mobilis, designated Z7 and Z10, were established using sucrose concentrations from 50 to 200 g/liter. Strain Z7 showed a higher invertase activity than Z10. Strain Z10 showed a reduced specific growth rate at high sucrose concentration while Z7 was unaffected. High sucrose hydrolyzing activity in strain Z7 lead to glucose accumulation in the medium at high sucrose concentrations. Ethanol production and fermentation time depend on the rate of catabolism of the products of sucrose hydrolysis, glucose and fructose. The metabolic quotients for sucrose utilization, qs, and ethanol production, qp (g/g·hr), are unsuitable for describing sucrose utilization by Zymomonas mobilis, as the logarithmic phase of growth precedes the phase of highest substrate utilization (g/liter·hr) and ethanol production (g/liter·hr) in batch culture.
Bioconversion of wheat straw to ethanol: Chemical modification, enzymatic hydrolysis, and fermentation
Authors: Detroy R. W. , Lindenfelser L. A. , Sommer S. , Orton W. L. 
Published: December 2004

AbstractNative wheat straw (WS) was pretreated with various concentrations of H2SO4 and NaOH followed by secondary treatments with ethylene diamine (EDA) and NH4OH prior to enzymatic saccharification. Conversion of the cellulosic component to sugar varied with the chemical modification steps. Treatment solely with alkali yield 51–75% conversion, depending on temperature. Acid treatment at elevated tempeatures showed a substantial decrease in the hemicellulose component, whereas EDA‐treated WS (acid pretreated) showed a 69–75% decrease in the lignin component. Acid‐pretreated EDA‐treated straw yielded a 98% conversion rate, followed by 83% for alkali–NH4OH treated straws. In other experiments, WS was pretreated with varying concentration of H2SO4 or NaOh followed by NH4OH treatment prior to enzymatic hydrolysis. Pretreatment of straw with 2% NaOH for 4 h coupled to enzymatic hydrolysis yield a 76% conversion of the cellulosic component. Acid–base combination pretreatment yielded only 43% conversions. A reactor column was subsequently used to measure modification–saccharification–fermentation for wheat straw conversion on a larger scale. Thirty percent conversions of wheat straw cellulosics to sugar were observed with subsequent fermentation to alcohol. The crude cellulase preparation yielded considerable quantities of xylose in addition to the glucose. Saccharified materials were fermented directly with actively proliferating proliferating yeast cells without concentration of the sugars.
Instabilities of product formation in a fed‐batch culture of Penicillium chrysogenum
Authors: Hegewald E. , Wolleschensky B. , Guthke R. , Neubert M. , Knorre W. A. 
Published: December 2004

AbstractBy investigation of a model of benzylpenicillin fermentation it was demonstrated that high fermentation productivity is connected with low stability. The increasing instability is not the result of external disturbances but of peculiarities inherent to the system. The main process variables and the essential parameters were selected by analysis of data obtained from fermentation runs in a pilot plant. By simulation on an analog computer it was shown that the proposed model gives a sufficient description of the kinetic behavior of the fermentation runs. By varying the initial conditions it was possible to obtain two types of fermentation runs. One type is distinguished by a high productivity connected with low initial concentrations of sucrose. An increase of the initial sucrose concentration also causes an increase of productivity. When a certain value of this concentration is exceeded a changeover to a faster growth of biomass takes place combined with the breakdown of productivity. The same phenomenon occurs at a defined initial concentration of sucrose if a disturbance of oxygen transfer rate takes place. Whether the culture stays in the one or in the other state after the disturbance has passed depends on the duration, the strength, and the beginning of the disturbance. In the pilot plant similar behavior can be observed. The sensitivity of fermentation processes to disturbances increases with the increase of productivity.
Hydrolysis of triglyceride by solid phase lipolytic enzymes of Rhizopus arrhizus in continuous reactor systems
Authors: Bell George , Todd John R. , Blain John A. , Patterson John D. E. , Shaw Charles E. L. 
Published: December 2004

AbstractContinuous hydrolysis of triglyceride in organic solvent systems using Rhizopus arrhizus mycelia as a source of insolubilized lipase has been studied in packed‐bed and stirred‐tank reactors. Typically a packed bed reactor containing 1 g of mycelia fed at 1 mL/min with a solution of 2.5% (w/v) olive oil in di‐isopropyl ether gave a fatty acid yield of 45% at 30°C. The optimum water concentration was found to be 0.17% (w/v) except under conditions of high oil feed concentration and high yield where no optimum was established. No temperature optimum was observed over the range 20–55°C. Calculated activation energies of 13–20 kJ/mol, depending on temperature, were lower, while Km(app) values of 0.1–0.3M were higher than those for hydrolysis in conventional aqueous emulsion systems. No evidence of any significant diffusional limitation, which could account for these values, was obtained. The mycelia showed a loss of activity of 0.6–1.0%h at 30°C. The packed bed proved markedly superior to the stirred tank for this system.
Fed‐batch culture: Modeling and application in the study of microbiol energetics
Authors: Esener A. A. , Roels J. A. , Kossen N. W. F. 
Published: December 2004

AbstractMicrobial growth in the fed‐batch mode is described by a simple unstructured model. The model is found to be in good agreement with agreement with the experimental observation, except under highly transient conditions. Extensive experimental data were collected and the energetics of the bacterium Klebsiella pneumoniae is evaluated. It is shown that the fed‐batch culti vation is a powerful experimental tool in the study of microbial kinetics and energetics simultaneously. Methods for determining the maintenance requirements are shown and evaluated. The maintenance coefficients determined from fed‐batch data are systematically smaller than those reported for continuous culture systems. Results suggest a decrease in maintenance demands at low specific growth rates.
Pulse response in an immobilized‐enzyme column: Elution profiles in reversible and consecutive reactions
Authors: Adachi Shuji , Hashimoto Kenji , Miyai Kiyosato , Kurome Hirokazu , Matsuno Ryuichi , Kamikubo Tadashi 
Published: December 2004

AbstractA pulse of substrate solution was applied to an immobilized‐enzyme column, in which the substrate was then converted by reversible or consecutive reactions. Immobilized glucose isomerase was used for the reversible reaction, and immobilized invertase and glucose oxidase for the consecutive reactions. The elution profiles of substrate and product were determined experimentally. These profiles were in good agreement with the ones predicted theoretically. The effect of some parameters on the elution profiles for reversible and consecutive reactions is discussed.