bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potentiometric quantitation of glycerol using immobilized glycerol dehydrogenase
Authors: Chen A. K. , Starzmann J. A. , Liu C. C. 
Published: December 2004

AbstractGlycerol dehydrogenase was immobilized in polyacrylamide gel layered over a small platinum screen and used to catalyze the oxidation of glycerol. In the presence of NAD+ and potassium ferricyanide, the coupling reaction generated a measurable electrical potential which was found to be Nernstian with respect to the glycerol concentration range of 10−4M to 10−1M. The reproducibility of the measurement and the optimal conditions for glycerol determination were described.
Production of SCP and cellulase by Aspergillus terreus from bagasse substrate
Authors: Garg S. K. , Neelakantan S. 
Published: December 2004

AbstractThe fermentation of 1.0% untreated bagasse under optimum cultural and nutritional conditions with Aspergillus terreus GN1 indicated that the maximum rate of protein and cellulase production could be obtained during three days of submerged fermentation. Even though 16.4% protein recovery, 0.55 units CMCase/mL, and 0.027 FPase units/mL were obtained on the seventh day, the rates of increase in protein recovery and cellulase production were slower than those obtained up to these days, which were 14.3% protein recovery, 0.45 units CMCase/mL, and 0.019 units FPase/mL. There was an initial lag in the utilization of cellulose up to two days due to the utilization of the water‐soluble carbohydrate present in untreated bagasse. Cellulose utilization and water‐soluble carbohydrate content during fermentation were correlated with protein recovery and enzyme production. The protein and cellulase production during three days fermentation with 1.0% untreated and treated bagasse were compared and the protein content of the total biomass was calculated and treated bagasse were compared and the protein content of the biomass was calculated into constituent protein contributed by the fungal mycelium and the under graded bagasse. The total biomass recovered with untreated and treated bagasse was 1020 and 820 mg/g bagasse substrate, respectively, and contained 14.3 and 20.6% crude protein, respectively. The contribution of fungal biomass and under graded bagasse was 309 and 711, and 373 and 447 mg/g untreated and treated bagasse substrates, respectively. In an 8‐L‐flask trial during three days of fermentation, the recovery of SCP and cellulase were 66 g and 32,400 units (Sigma) for treated bagasse and 82 g and 8200 units (Sigma) for untreated bagasse, respectively.
On the mechanism of immobilized glucose oxidase deactivation by hydrogen peroxide
Authors: Malikkides Christakis O. , Weiland Ralph H. 
Published: December 2004

AbstractThe result of experiments in a fixed‐bed reactor containing glucose oxidase immobilized on a nonporous support and conducted in the absence of diffusional limitations are reported. Kinetic parameters were established by separate batch experiments. The key observation was that, in every case, poisoning by product hydrogen peroxide resulted in a minimum in enzyme activity in the interior of the bed, well away from the ends. The deactivation data were interpreted by fitting the rate constant for poisoning, the only free parameter, to a previously reported theory. The theory postulates several deactivation mechanisms each of which leads to self‐consistent kinetics, but the only mechanism which fitted the data assumes that peroxide attack the enzyme when it is the from complexed with glucose. Theory and experiment agreed to within the accuracy (± 2%) of the activity measurements.
Removal rates of bacterial cells from glass surfaces by fluid shear
Authors: Powell Martin S. , Slater Nigel K. H. 
Published: December 2004

AbstractA simple kinetic relationship is proposed to model the rate of removal of bacterial cells from solid surface by a shearing force. The theory is compared to experimentally obtained data for the removal of B. cereus cells from glass capillaries, the shear being imparted by a the flow of medium through the capillary. The critical shear stress required to sterilize the capillary wall is obtained experimentally for a number of industrial contaminant bacteria. The effect of settling time on critical shear stress is also investigated.
On the role of reversible denaturation (unfolding) in the irreversible thermal inactivation of enzymes
Authors: Zale Stephen E. , Klibanov Alexander M. 
Published: December 2004

AbstractThe contribution of the reversible thermal unfolding of an enzyme toward the overall irreversible thermoinactivation process has been examined both theoretically and experimentally. Using bovine pancreatic ribonuclease as a model, we have studied the effect of such variables as pH and salts both on the equilibrium constant of reversible denaturation and on the rate constant of the overall irreversible process. It has been demonstrated that at temperatures where a significant fraction of the enzyme molecules are in the native conformation, there is a correlation between the enzyme thermostabilities with respect to the reversible and irreversible inactivations: greater stability against the former is accompanied by greater stability against the latter. On the other hand, at very high temperatures (where essentially all of the enzyme molecules are unfolded), such a correlation does not exist. These findings are considered in terms of a kinetic model for irreversible enzyme thermoinactivation, and the implications of the derived relationship are discussed.
Ethanol from whey: Continuous fermentation with cell recycle
Authors: Janssens J. H. , Bernard A. , Bailey R. B. 
Published: December 2004

AbstractThe production of ethanol from cheese whey lactose has been demonstrated using a single‐stage continuous culture fermentation with 100% cell recycle. In a two‐step process, an aerobic fed batch operation was used initially to allow biomass buildup in the absence of inhibitory ethanol concentrations. In the anaerobic ethanol‐producing second step, a strain of Kluyveromyces fragilis selected on the basis of batch fermentation data had a maximum productivity of 7.1 g ethanol/L/h at a dilution rate of 0.15 h−1, while achieving the goal of zero residual sugar concentration. The fermentation productivity diminished when the feed sugar concentation exceeded 120 g/L despite the inclusion of a lipid mixture previous shown to enhance batch fermentation productivities.
Multistage continuous culture to examine secondary metabolite formation in plant cells: Phenolics from Nicotiana tabacum
Authors: Sahai O. P. , Shuler M. L. 
Published: December 2004

AbstractThe feasibility of operating a multistage continuous culture of plant cells was demonstrated for Nicotiana tabacum. Cells in the second stage of a two‐stage chemostat were morphologically distinct from cells in the first stage or cells in a single‐stage unit with a holding time equal to the combined holding times in the two‐stage system. Cells in the second stage produced much higher levels of phenolics per unit weight of cells than cells in either the first‐stage or single‐stage unit. The steady‐state was reproduced. When a glucose side stream was fed to the second stage, an increase in apparent cell division was observed with a simultaneous decrease in phenolics productivity. When the toxic precursor phenylalanine was pulsed into the reactor, the quantity of biomass decreased temporarily while phenolic productivity increased. These experiments demonstrate that multistage continuous culture may be useful in increasing secondary metabolite formation in cells and in exploring mechanisms controlling secondary metabolite formation.
Algal autoflocculation—verification and proposed mechanism
Authors: Sukenik A. , Shelef G. 
Published: December 2004

AbstractBiomass autoflocculation in outdoor algal cultures was found to be associated with increases of culture pH levels, due to CO2 consumption by the algal photosynthetic activity. Under these alkaline conditions, some medium chemical ions precipitated together with the algal biomass. The chemical substances involved with the process and its dependence on pH value were studied by simulation of autoflocculation in laboratory experiments. Proper concentrations of calcium and orthophosphate ions in the medium are important for autoflocculation and, in order to attain it within the pH range 8.5–9.0, the culture should contain 0.1mM–0.2mM orthophosphate and 1.5mM–2.5mM calcium prior to raising the pH level. Calcium phosphate precipitates are considered as the flocculating agent which reacts with the negatively charged surface of the algae and promotes aggregation and flocculation.
Kinetics of the enzymatic hydrolysis of cellulose
Authors: Wald Stephen , Wilke Charles R. , Blanch Harvey W. 
Published: December 2004

AbstractEnzymatic hydrolysis of cellulose for sugar production offers advantages of higher conversion, minimal by‐product formation, low energy requirements, and mild operating conditions over other chemical conversions. The development of a kinetic model, based on observable, macroscopic properties of the overall system, is helpful in design and economic evaluation of processes for sugar conversion and ethanol production. A kinetic model is presented, incorporating enzyme adsorption, product inhibition, and considers a multiple enzyme and substrate system. This model was capable of simulating saccharification of a lignocellulosic material, rice straw, at high substrate (up to 333 g/L) and enzyme concentrations (up to 9.2 FPU/mL) that are common to proposed process designs.
Ethanol production by Zymomonas mobilis in fed‐batch fermentations
Authors: Silman R. W. 
Published: December 2004

AbstractThe production of ethanol by Zymomonas mobilis NRRL B‐4286 was studied in fed‐batch cultures. Initial percent (w/v) glucose, rate of feed, and quantity of 50%; (w/v) glucose feed were varied. Glucose inhibition of growth rate occurred at concentrations greater than 8% (w/) Feed was begun after 4 h incubation. Feed volume was ca. 36%; of starting batch volume to get ca. 10%; (w/v) ethanol at harvest. The range of feed rates studied varied from 16%; batch volume/h (glucose concentration increased to an inhibitory level) to 4%; batch volume/h (glucose concentration dropped rapidly to zero and was limiting). Increasing feed volume to 46%; of starting volume at the best feed rate (ca. 10%; feed volume/h) increased final ethanol concentration to 11.3%; (w/v). However, the resultant increase in fermentation time from ca. 21 to 29 h decreased ethanol volumetric productivity from 5.2 to 4.6 g/L h.
Development of a continuous process for metal accumulation by Zoogloea ramigera
Authors: Norberg Anders , Rydin Stefan 
Published: December 2004

AbstractBiomass, mainly consisting of an acidic polysaccharide produced by Zoogloea ramigera, has been used as an adsorbing agent in a continuous process for the recovery of metal. The adsorption of copper has been studied with respect to retention time, biomass concentration, and reaction pH, in order to determine the optimal conditions for copper recovery. The results indicate that the uptake of copper is rapid and efficient. About 0.17 g Cu is adsorbed per gram of biomass within 10 min. At high biomass concentrations, the total amount of copper removed from solution is high, but the specific amount of copper adsorbed to biomass is low. The biomass exhibits a higher adsorptive uptake at low concentrations.
A new modeling technique and computer simulation of bacterial growth
Authors: Papageorgakopoulou H. , Maier Walter J. 
Published: December 2004

AbstractA mathematical model that describes substrate utilization and cell growth in terms of two potentially rate‐limiting enzyme systems has been developed. Consideration of substrate inhibition and enzyme repression have been incorporated. The model provides a rational approach for characterizing non‐steady‐state phenomena. The model has been used to analyze batch test data to illustrate the effects of inhibition, repression, and concurrent substrate utilization. Its utility lies in the fact that it provides a quantitative framework for describing changes in the activity levels of cells that result from changes in substrate concentration and/or substrate type. The lag phase resulting from exposure to a new substrate can be modeled.
The Production ofL‐serine with a methylotrophic microorganism using theL‐serine pathway and coupling with anL‐tryptophan‐producing process
Authors: Behrendt U. , Bang W. G. , Wagner F. 
Published: December 2004

AbstractThe cultural conditions for the production of enhanced formation of L‐serine (up to 7 g/L) are described with the methylotrophic bacteriumPseudomonas3 ab (DSM 672). The batch process is divided into three parts: (1) the biomass production phase, (2) substrate limitation period, and (3) L‐serine accumulation phase. The initial specific production rate ofqp= 0.1 g L‐serine/g dry wt/h is based on the inhibition of the L‐serine pathway. This is accomplished by high precursor concentrations (glycine) and a pH shift to pH 8.5. The enzymatic background is discussed. Furthermore, a coupling of the L‐serine process with a L‐tryptophan‐producing process is demonstrated.
Alcoholic fermentation of raw cassava starch by Rhizopus koji without cooking
Authors: Fujio Yusaku , Suyanadona Puangpen , Attasampunna Poonsook , Ueda Seinosuke 
Published: December 2004

AbstractUsing only wheat bran koji from the Rhizopus strain, raw cassava starch and cassava pellets converted reasonably well to alcohol (ethanol) without cooking at 35°C and pH 4.5–5.0. When the initial broth contained 30 g raw cassava starch, 10 g Rhizopus sp. koji, and 100 mL tap water, 12.1 g of alcohol was recovered by final distillation from fermented broth. In this case, 12.1 g alcohol corresponds to an 85.5% conversion rate based on the theoretical values of the starch content. When the initial broth contained 40 g cassava starch, 14.1 g of alcohol was recovered, where 14.1 g corresponds to a 74.5% conversion rate. The alcoholic fermentation process described in the present work is considered more effective and reasonable than the process using raw starch without cooking reported until now, since the new process makes it unnecessary to add yeast cells and glucoamylase preparation.
Alcoholic fermentation: Modelling based on sole substrate and product measurement
Authors: Bovee J. P. , Strehaiano P. , Goma G. , Sevely Y. 
Published: December 2004

AbstractOptimal automatic bioreactor control requires a mathematical model adapted to the potency of reliable sensors. A new relationship describing the kinetic behavior of alcoholic fermentation is discussed. By analogy with chemical kinetics, the biological rate of substrate consumption is related to substrate and product concentration by the following equation:

Using the well known yield relation between product and substrate, it is possible to describe in both batch and continuous cultures the ethanol and sugar concentrations versus time. This pattern has been successfully tested on several fermentations performed by yeasts (S. cerevisiae, S. bayanus, and S. cerevisiae sake) and a bacterium (Z. mobilis). This simple relationship is proposed as a tool for process control alcoholic fermentation.
An adaptive control algorithm for fed‐batch culture
Authors: Stanišsis J. , Levišauskas D. 
Published: December 2004

AbstractThe implementation of adaptive control for a fed‐batch culture in order to maximize the output of product based on a self‐adjusting model is discussed in the present work. Optimization methods were applied to the generalized mathematical model of a fed‐batch fermentation process to determine control algorithms that could be used for on‐line process control. The efficiency of the proposed adaptive algorithms was investigated by simulating a model system. The model of amylotytic enzyme fermentation that was proposed by the authors was taken from a real process. Dynamic modelling has shown that the main problem of realization is connected with the on‐line identification of the adaptive model's parameters. To avoid this problem, we have introduced special limitations on the parameters' time variations that increased the convergence of the identification algorithm. The results of the investigation have shown the efficiency of the proposed adaptive algorithms, and the results of this work should be investigated for real process control.
The hydroxylation of biphenyl by Aspergillus toxicarius: Conditions for a bench scale fermentation process
Authors: Golbeck John H. , Cox John C. 
Published: December 2004

AbstractFungi of the Aspergillus sp. can hydroxyate biphenyl to 4,4′‐dihydroxybiphenyl, a chemical intermediate used in the plastics industry. The authors studied various batch culture conditions for the production of 4,4′‐dihydroxybiphenyl, by Aspergillus toxicarius, in 25‐mL shake flasks and 2‐L fermenter cultures. Conditions investigated included temperature, aeration, carbon and nitrogen sources, biomass content, and time of substrate addition. Under optimum conditions we observed a rate of 4,4′‐dihydroxybiphenyl production of 15–20 mg/day/g dry wt mycelia. Such a production rate is probably too low to support a commercial process and possible reasons for the low productivity are discussed.
Analysis of a continuous, aerobic, fixed‐film bioreactor. I. Steady‐state behavior
Authors: Park Young , Davis Mark E. , Wallis David A. 
Published: December 2004

AbstractThe analysis of a continuous, aerobic, fixed‐film bioreactor is performed by simulating the behavior of penicillin production in a three‐phase fluidized bed. Rigorous mathematical models are developed for a fluidized‐bed fermentor in which bioparticles are fluidized by the liquid medium and air. The steady‐state performance of the fluidized‐bed reactor is appraised in terms of penicillin productivity and outlet concentration by considering the two extremes in contacting patterns, complete back‐mix and plug flow, in the absence of a growing biofilm. The results show that the complete back‐mix contacting pattern is preferred over that of plug flow due to the nature of the penicillin kinetic relationships. It is also shown that for the dual‐nutrient (glucose and oxygen) penicillin reaction system the optimum biofilm thickness does not equal the penetration depth of a limiting nutrient, but depends upon the total reactor configuration.
Analysis of a continuous, aerobic, fixed‐film bioreactor. II. Dynamic behavior
Authors: Park Young , Davis Mark E. , Wallis David A. 
Published: December 2004

AbstractThe dynamic analysis of a continuous, aerobic, fixed‐film bioreactor has been performed. Rigorous mathematical models have been developed for a fluidized‐bed fermentor with biofilm growth. The transient performance of the reactor is appraised in terms of outlet penicillin concentration for constant, as well as variable carbon substrate feed rates. The effect of the reactor oxygen transfer capacity is elucidated for those cases employing substrate feeding strategies. The results show that penicillin production in a continuous, fixed‐film bioreactor reaches a maximum with processing time, but subsequently decreases as cell mass accumulates and substrate deficiencies occur. The maximum production level can be maintained for increased operating times if the substrate supply is continuously increased. The duration of this prolonged production is a direct function of the rate of increase and the operating time at which the increase is initiated. The oxygen transfer capacity of the reactor was found to be important to the effectiveness of a feeding strategy.
A modified matrix perfusion–microcarrier bead cell culture system. I. Adaptation of the matrix perfusion system for growth of human foreskin fibroblasts
Authors: Strand Janie M. , Quarles John M. , McConnell Stewart 
Published: December 2004

AbstractTwo strains of human foreskin fibroblast cells were incapable of sustained growth in a matrix perfusion culture system, possibly because of their inability to attach to the fiber surfaces. Addition of microcarrier beads to the extracapillary space allowed attaining high cell densities in excess of 107 cells per culture unit. Microcarrier beads were tested in hollow fiber culture devices containing membranes of 104 or 105 D nominal porosities. Best results were obtained when initial cell densities of at least (2–3) × 106 cells were used in units with 105 D pore size membranes and DEAE–Sephadex or polyacryl‐amide microcarrier beads in the extracapillary space. This extension of the matrix perfusion system should be useful for growing other anchorage dependent cells while retaining the advantages of perfusion culture.
Interaction of proteins with Triton X‐100‐substituted sepharose 4B
Authors: Nemat‐Gorgani Mohsen , Karimian Khashayar 
Published: December 2004

AbstractInteraction of a number of arbitrarily chosen proteins with Triton X‐100‐substituted Sepharose 4B has been investigated. Of the proteins examined, bovine serum albumin, hemoglobin, glutamate dehydrogenase, and pepsin were found immobilized on the adsorbent. Binding of these proteins occurred irrespective of pH and NaCl concentration. Cytochrome c, used as a model protein, was totally immobilized only at low pH. Adsorption of glutamate dehydrogenase and pepsin took place with retention of their catalytic activities. Moreover, glutamate dehydrogenase used as a model allosteric enzyme, was found to retain its native properties upon binding to the adsorbent in the forms of suspension or column. Results are discussed in terms of specific interactions involving the hydrophobic region of Triton X‐100 and the apolar patches or crevices present on the surface of protein molecules. Possible potential of the matrix as a method for preparation of biologically active immobilized proteins and its application in continuous operations are also discussed.
Application of bioenergetics to modelling the microbial conversion of D‐xylose to 2,3‐butanediol
Authors: Jansen Norman B. , Flickinger Michael C. , Tsao George T. 
Published: December 2004

AbstractDuring the oxygen limiting growth of Klebsiella oxytoca, the xylose metabolism may be considered as consisting of three components: conversion to 2,3‐butanediol by “fermentation,” oxidation to carbon dioxide by respiration, and assimilation to cell mass. The amount of energy required for the assimilation of cell mass is assumed to determine the extent to which the two energy producing reactions occur. The activity of each energy producing pathway is also determined by the availability of oxygen and by the energy yield of each pathway. These relationships can be quantified by equating the ATP required for growth and maintenance to the ATP produced by the energy producing reactions. The resulting equation for butanediol production appears similar to the Luedeking and Piret model where the parameters α and β are related to the maximum cell yield from ATP and the maintenance energy requirement. These parameters were estimated from 14 batch fermentations, and the resulting simulation was used to describe the effects of the oxygen transfer rate and the initial xylose concentration on the yields and rates of the 2,3‐butanediol fermentation.
Immobilized cyclomaltodextrin glucanotransferase of an alkalophilic Bacillus sp. No. 38‐2
Authors: Kato Takashi , Horikoshi Koki 
Published: December 2004

AbstractCyclomaltodextrin glucanotransferase [1,4‐α‐D‐glucan‐4‐α‐D‐(1,4‐α‐D‐glucano)–transferase (cyclizing), E.C.−2.4.1.19] of an alkalophilic Bacillus sp. No. 38‐2 (ATCC 21783), which contains three types of enzymes (acid, neutral, and alkaline enzymes), was immobilized on synthetic adsorption resin. No distinguishing changes in pH or thermal stabilities of enzyme were observed due to the immobilization. Since acid–enzyme activity had disappeared, the optimum pH of immobilized enzyme was 9.0. Optimum temperature for the enzyme activity changed from 50 to 55°C. The enzyme converted starch to cyclodextrins without significant loss of activity under the conditions of continuous reaction for about two weeks by using the column system (60°C at pH 8.0). About 63% of soluble starch solution [4% (w/v)] was changed to cyclodextrins, as tested so far.