bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enhanced product formation in continuous fermentations with microbial cell recycle*
Authors: Bull Daniel N. , Young Mark D. 
Published: December 2004

AbstractThe effect of partial recycle of microbial cells on the operation of a chemostat has been investigated for two fermentations. Stable steady states without partial cell recycle were obtained for the conversion of D‐sorbitol to L‐sorbose by Gluconobacter oxydans subsp. suboxydans 1916B and for the conversion of glucose to 2‐ketogluconic acid by Serratia marcescens NRRL B‐486. The employment of partial cell recycle dramatically increased product formation rates for both fermentations.
Automated fermentation equipment I. program‐controlled fermentor
Authors: Veres A. , Nyeste L. , Kurucz I. , Kirchknopf L. , Szigeti L. , Holló J. 
Published: December 2004

AbstractA fermentation system with a plug scheme unit has been developed, offering a variety of solutions to measurement, control, and operational problems. By means of the program unit, e.g., automatic pH control assigned to the dynamic of batch cultures and the feed of different ingredients controlled by a time program or a given variable have been solved. The continuous culture volume was controlled by a level controlled by a level controller equipped with a photosensor. A method was developed for variable control that provide information on the activity of the culture, and allows direct measurement of the different rate values, e.g., generation time or specific product formation rate. Applicability of the direct measurement of generation time is presented in the qualification of molasses and in a static off‐line optimization process.
Automated fermentation equipment II. Computer–fermentor system
Authors: Nyeste L. , Szigeti L. , Veres A. , Pungor E. , Kurucz I. , Holló J. 
Published: December 2004

AbstractAn expensive computer‐operated system suitable for data collection and steady‐state optimum control of fermentation processes is presented. With this system, minimum generation time has been determined as a function of temperature and pH in the turbidostat cultivation of a yeast strain. The applicability of the computer‐fermentor system is also presented by the determination of the dynamic KLa value.
Environmental phenotypic variation of Scenedesmus dimorphus in high‐rate algae ponds and its relationship to wastewater treatment and biomass production
Authors: Oron Gideon , Shelef Gedaliah , Levi Anna 
Published: December 2004

AbstractDuring the course of operating high‐rate algae ponds (HRAP) for wastewater treatment and protein production, changes were found in the two main algae species. The observed changes were interpreted to be a reflection of the operation regime and loading combined with environmental conditions. To verify that these changes were phenotypic and not genetic, experiments were conducted on Scenedesmus dimorphus growing in miniponds (110 L) as well as in the laboratory. The results showed that the changes in S. dimorphus were external and due to the changes in the loading and operating conditions of the ponds adjusted to changing environmental conditions. It was found that wastewater treatment efficiency and algal yield are also correlated with the S. dimorphus type.
Enzyme stabilization by linear chain polymers in ultrafiltration membrane reactors
Authors: Greco Guido , Gianfreda Liliana 
Published: December 2004

AbstractThe experimental results discussed in this article concern p‐nitrophenylphosphate hydrolysis by acid phosphatase in an Ultrafiltration membrane reactor. The basic conclusions drawn are: (1) Linking the enzyme to a soluble support does not give rise to an increase in its stability while the chemical manipulations involved result in marked reductions in enzymic activity. (2) Enzyme entrapment within a proteic gel produces a considerable increase in its thermal stability as compared to the diluted native enzyme; this presumably stems from drastic reductions in enzyme mobility. (3) Correspondingly, considerable reductions occur in enzyme activity that depend on substrate mass transfer resistances within the gel layer. (4) Small amounts of linear chain water‐soluble synthetic polymers (polyacrylamides) give rise to high macromolecular concentration levels in the reactor region where the enzyme is dynamically immobilized and produce the same enzyme stabilization as gel entrapment. (5) Only minor substrate mass transfer limitations take place in this region and hence enzyme activity is virtually unaffected. (6) Both effects (stabilization and slight activity reduction) seem not to depend strongly on the characteristics of the soluble polymer (molecular weight and ionic character).
The activity of immobilized enzymes on different krill chitin preparations
Authors: Synowiecki Józef , Sikorski Zdzisław E. , Naczk Marian 
Published: December 2004

AbstractThe suitability of krill chitin, prepared by using different concentrations of KOH and HCI for deproteinization and demineralization, respectively, was investigated. The activity of enzymes immobilized on such supports depends on the degree of deproteinization of chitin, availability of amino groups, content of minerals, mesh size, structure of the surface, and conformation of the chitin molecules. It was found that invertase and amyloglucosidase achieved high activity after immobilization on chitin obtained at not too rigorous conditions of deproteinization. However, the activity of immobilized α‐amylase and diastase increased significantly with the increase in concentration of KOH used for deproteinization. High content of minerals and proteins in chitin preparation causes a loss of immobilized enzyme activity.
Effect of oxygen transfer rate on the composition of the pectolytic enzyme complex of Aspergillus niger
Authors: Zetelaki‐Horváth K. , Vas K. 
Published: December 2004

AbstractOptimal agitation and aeration conditions [assuring O2 transfer rates (OTR) from 12 to 179 mmol L−1 h−1] were determined for pectin lyase (PL) synthesis of an Aspergillus niger strain. Components of the pectolytic enzyme complex were also investigated in order to determine whether their O2 demand is identical with or different from that of pectin lyase. Should the latter be the case, a possibility would be given to produce enzyme complexes of different agitation and aeration conditions. According to our results, mycelium yield of Aspergillus niger attained a maximum at an OTR of 100 mmol L−1 h−1. The yields of the various pectolytic enzymes reached maxima at different OTRs. Pectin lyase production was the highest (0.555 µmol min−1 mL−1) at an OTR of 60 mmol L−1 h−1. Endopolygalacturonase (PG) production showed a maximum at the OTR of 49 mmol L−1 h−1 with a second peak at 100−135 mmol O2 L−1 h−1. Pectin esterase (PE) synthesis showed a maximum at on OTR of 12−14 mmol L−1 h−1, while both apple juice clarifying and macerating activities gave two maxima at 14 and 60 mmol L−1 h−1 due to the optima of PE and endo‐PG. Macerating activity showed a high value at OTR optimal for PL production as well.
A CSTR‐hollow fiber system for continuous hydrolysis of proteins. Performance and kinetics
Authors: Deeslie W. David , Cheryan Munir 
Published: December 2004

AbstractThe effect of four operating variables (enzyme concentration, substrate concentration, flow rate, and reaction volume) on the performance of CSTR‐hollow fiber membrane reactor was studied for the continuous hydrolysis of a soy protein isolate using Pronase. Based on a residence time distribution study, the reactor system was modeled as an ideal CSTR in combination with the Michaelis‐Menten equation of enzyme kinetics. This kinetic model correlated conversion with a space‐time parameter modified to include all four independent variables. An empirical model based on curvilinear regression analysis was also developed. Both models predicted conversion fairly well, although the kinetic model slightly underpredicts at high conversion.
Preparation and properties of immobilized amyloglucosidase
Authors: Nithianandam V. S. , Srinivasan K. S. V. , Joseph K. Thomas , Santappa M. 
Published: December 2004

AbstractAmyloglucosidase was immobilized on a copolymer of methyl methacrylate and 2‐dimethylaminoethyl methacrylate. The resulting immobilized amyloglucosidase has 19% of the soluble enzyme specific activity. The pH optimum of immobilized amyloglucosidase is shifted towards acidity by 1.9 units. The temperature optimum of immobilized enzyme is shifted upward by 5°C. The immobilized amyloglucosidase has the maximum stability at pH 4.6, whereas the soluble enzyme has maximum stability at pH 5.5. While soluble amyloglucosidase has a maximum thermal stability at 50°C, the stability of the immobilized amyloglucosidase steadily decreases with the increase in temperature.
The potential of biological methane generation from chicken manure
Authors: Huang James J. H. , Shih Jason C. H. 
Published: December 2004

AbstractThe potential for biological methane generating from the manure of laying hens was investigated in the laboratory. Fresh manure was collected, analyzed, and used to prepare medium for bacterial growth. At 55°C and under anaerobic conditions, methanogenic cultures were initiated by incubating the medium with different inoculations from various natural environments. Since there were no significant differences in gas production among these initiated cultures after 40 days of acclimation, they were mixed to maintain a genetic pool. The mixed culture was then challenged with different retention times (RT) and different volatile solid (VS) concentrations for the selection of optimal conditions and cultures. The conditions were finally selected to be 4‐day RT and 6% VS for the maximal rate of gas production. The optimal pH and temperature were determined to be 7.5 and 50°C, respectively. Under such conditions the selected culture produced total gas at a rate 4.5 L/L day and methane (70% of total gas) 3.2 L/L day. The chicken manure therefore was able to support the methane yield at 270 L/kg of VS, a value comparably higher than other kinds of livestock wastes.
Continuous cultivation of fission yeast: Analysis of single‐cell protein synthesis kinetics
Authors: Agar D. W. , Bailey J. E. 
Published: December 2004

AbstractA fundamental problem in microbial reactor analysis is identification of the relationship between environment and individual cell metabolic activity. Population balance equations provide a link between experimental measurements of composition frequency functions in microbial populations on the one hand and macromolecular synthesis kinetics and cell division control parameters for single cells on the other. Flow microfluorometry measurements of frequency functions for single‐cell protein content in Schizosaccharomyces pombe in balanced exponential growth have been analyzed by two different methods. One approach utilizes the integrated form of the population balance equation known as the Collins‐Richmond equation, and the other method involves optimization of parameters in assumed kinetic and cell division functional forms in order to best fit measured frequency functions with corresponding model solutions. Both data interpretation techniques indicate that rates of protein synthesis increase most in small protein content cells as the population specific growth rate increases, leading to parabolic single‐cell protein synthesis kinetics at large specific growth rates. Utilization of frequency function data for an asynchronous population is shown in this case to be a far more sensitive method for determination of single‐cell kinetics than is monitoring the metabolic dynamics of a single cell or, equivalently, synchronous culture analyses.
Application of data consistency tests and new parameter estimation methods to microbial growth on corn dust in batch culture
Authors: Solomon B. O. , Erickson L. E. , Hess J. L. 
Published: December 2004

AbstractThe microorganism Candida utilis was grown on both filtered and unfiltered substrate obtained from enzymatic hydrolysis of starch in corn dust. For growth on filtered substrate, the average integrated biomass energetic yield value based on biomass‐substrate data was η = 0.55 and for growth on unfiltered substrate an average yield value of η = 0.59 was obtained. Material and energy balances showed that the presence of unfiltered corn residue in the media had no significant effect on the yields. Statistical methods were developed and used to obtain best estimates of the growth parameters. Values of the biomass energetic yield corrected for maintenance (ηmax = 0.619) and the maintenance coefficient (me = 0.043) were obtained for growth on filtered substrate. Values of ηmax = 0.741 and me = 0.142 were obtained for the growth on unfiltered substrate. The consistency of data and parameter estimates was relatively good for filtered substrate; however, parameter estimates for unfiltered substrate were not consistent. Growth experiments without filtration of the products of starch hydrolysis resulted in protein‐enriched products with about 39.73% protein.
Growth of Saccharomycopsis fibuligera in a continuous‐stirred‐tank fermentor
Authors: Admassu Wudneh , Korus Roger A. , Heimsch Richard C. , Lemmel Steven A. 
Published: December 2004

AbstractGrowth rates and amylase production rates were determined for the yeast Saccharomycopsis fibuligera grown on a simulated potato processing waste in a continuous‐stirred‐tank fermentor. S. fibuligera formed large multicellular flocs in the fermentor, and cell growth was reduced at low dilution rates because of mass‐transfer resistance. The average Thiele modulus, which is the measure of extent of substrate diffusion, had a value ranging from ϕav = 2.2 for D = 0.10 to 0.3 for D = 0.40. Growth rates were described by the Monod equation modified to include mass‐transfer effects. This modified Monod equation was used to predict growth rates from measured floc‐size distribution. Experimentally determined growth rates were in close agreement with these predicted values.
Experimental bioenergetics ofSaccharomyces cerevisiae in respiration and fermentation
Authors: Yerushalmi L. , Volesky B. 
Published: December 2004

AbstractAerobic growth of Saccharomyces cerevisiae on glucose was investigated, focusing on the heat evolution as it relates to biomass and ethanol synthesis. “Aerobic fermentation” and “aerobic respiration” were established respectively in the experimental system by performing batch and fed‐batch experiments. “Balanced growth” batch cultivations were carried out with initial sugar concentrations ranging from 10 to 70 g/L, resulting in different degrees of catabolite repression. The fermentative heat generation was continuously monitored in addition to the key culture parameters such as ethanol production rate, CO2 evolution rate, O2 uptake rate, specific growth rate, and sugar consumption rate. The respective variations of the above quantities reflecting the variations in the catabolic activity of the culture were studied. This was done in order to evaluate the microbial regulatory system, the energetics of microbial growth including the rate of heat evolution and the distribution of organic substrate between respiration and fermentation. This study was supported by closing C, energy, and electron balances on the system.The comparison of the fractions of substrate energy evolved as heat (δh) with the fraction of available electrons transferred to oxygen (ϵO2) indicated equal values of the two (0.46) in the aerobic respiration (fed‐batch cultivation). However, the glucose effect in batch cultivations resulted in smaller ϵO2 than δh, while both values decreased in their absolute values. The evaluation of the heat energetic yield coefficients, together with the fraction of the available electrons transferred to O, contributed to the estimation of the extent of heat production through oxidative phosphorylation.
Evaluation of crude dextran as phase‐forming polymer for the extraction of enzymes in aqueous two‐phase systems in large scale
Authors: Kroner K. H. , Hustedt H. , Kula M.‐R. 
Published: December 2004

AbstractA detailed study of the influence of crude dextran on enzyme extractions in aqueous phase systems is presented in this article. The physical parameters of crude dextran, a purified T‐500 fraction from Pharmacia, and a hydrolyzed crude dextran are compared and their influence on the phase system parameters investigated. Initially there is a drastic increase in the viscosity of the lower dextran‐rich phase and a significant shift in the macroscopic structure of these phases, observed as the “gel‐forming” properties of the dextran phases. The latter can be important for the partition of any enzyme by influencing the effect of phosphate concentration on the partition of proteins, although these experiments show that the partition coefficient of several enzymes is not much altered. The partition parameters allow the substitution of Dextran T‐500 fractions by crude dextran or unfractionated, slightly hydrolyzed fractions. Using crude dextrans the performance and technical realization of enzyme extraction processes are demonstrated for pullulanase from Klebsiella pneumoniae and formate dehydrogenase from Candida boidinii.Both enzymes were recovered in comparable high yields. The equipment performance was quite good, as indicated by the high throughput values of the separators employed. Especially when using nozzle separators for phase separation there is a better performance in comparison to the Dextran T‐500 fraction. No serious technical problems were encountered when replacing the expensive fractionated dextran with a crude dextran. In this way aqueous two‐phase systems containing dextran become more feasible for enzyme purification from an economic point of view. The price of about 1.30 German marks (DM) per liter for a useful phase system already appears acceptable for the production of valuable intracellular enzymes.
Analysis and optimization of methods using water‐soluble carbodiimide for immobilization of biochemicals to porous glass
Authors: Janolino Violeta G. , Swaisgood Harold E. 
Published: December 2004

AbstractTwo methods employing a water‐soluble carbodiimide for carboxyl activation were investigated for the immobilization of biochemicals to succinamidopropyl‐porous glass beads. Immobilization using the simultaneous method (simultaneous addition of carbodiimide and nucleophilic ligand to the beads) and large excess of carbodiimide and a small nucleophile should result in covalent binding to all accessible carboxyl groups. Results obtained with glycine methyl ester indicated that 40% of the total surface carboxyl groups were sterically accessible. Using these reaction conditions with the protein, chymotrypsinogen, suggests that a surface monolayer is immobilized. although far fewer sites are required assuming single point attachment. For ligands containing carboxyl groups and several nucleophilic groups (e. g., enzymes), however, biological inactivation may occur using the simultaneous method. Consequently, a sequential method (activation of the surface with carbodiimide followed by washing and addition of the biochemical to be immobilized) was optimized. Using optimal conditions (20 min activation time at pH 4.75 and room temperature; 2 min wash at pH 7 and 0°C) and 0.1M carbodiimide, nearly half of the accessible surface sites remained in the O‐acylisourea form and reacted with glycine methyl ester upon its addition. The amount of surface loading as a function of activation time was consistent with a model constructed using rate constants for O‐acylisourea formation and hydrolysis previously derived from solution studies with acetic acid [Swaisgood and Natake, J. Biochem 74, 77 (1973)]. Measurement of reaction rates with glycine methyl ester following surface activation suggests that the rate of reaction with amino groups is at least eightfold greater than the hydrolysis rate. Either immobilization procedure gave comparable enzyme loading and specific activities for the case of sulfhydryl oxidase.
Quantitative measurement of oxygen consumption in insect cell culture infected with polyhedrosis virus
Authors: Weiss S. A. , Orr T. , Smith G. C. , Kalter S. S. , Vaughn J. L. , Dougherty E. M. 
Published: December 2004

AbstractA simple and reproducible quantitative method for measuring dissolved oxygen (DO) in uninfected and baculovirus infected cells in culture is described. To establish this method, an industrial DO measuring system for fermentation was employed. During this process the physical characteristics of the cell culture vessel were taken into account permitting a direct readout of DO in microliters per vessel. During these studies, it was experimentally documented that insect cells, particularly baculovirus infected cells, in culture from 1 to 14 days utilize an appreciable level of DO.
Studies on Scenedesmus acutus growth. The incorporation of 14C‐glucose by Scenedesmus acutus under light and dark periods
Authors: Shamala T. R. , Drawert F. , Leupold G. , Becker W. 
Published: December 2004

AbstractQualitative and quantitative estimations of alcohol‐extractable compounds from 14C‐glucose‐incorporated Scendesmus acutus cells were performed at various intervals of time. After two hours of incubation with 14C‐glucose in light, amino acids were synthesized at 65% and sucrose at 26% of the total input label. In the dark incorporation, 30% of the total radioactivity was found in amino acids and 46% in sucrose. Leucine and valine were detected only during the oxidation of glucose in light. The concentration of serine increased more in the presence of light, as compared to dark. These results on the oxidation of glucose are discussed in this article.
The use of continuous cultures for selection and isolation of microorganisms producing extracellular enzymes adapted to extreme environments
Authors: Lelieveld H. L. M. 
Published: December 2004

AbstractMicroorganisms producing extracellular enzymes with special properties can be selected and isolated by growing them in continous culture and using as the growth‐limiting substrate a substance which must be broken down by the enzyme of interest. A diffusion layer around the microbial cell will cause gradients in the concentrations of enzymes and the hydrolyzed substrate. This will cause differences in growth rates between the parent cells and those mutant cells which produce an enzyme better adapted to the selective environment provided.
Modeling enzyme immobilization in porous solid supports
Authors: Do Duong D. , Clark Douglas S. , Bailey James E. 
Published: December 2004

AbstractEnzymes are often immobilized on the internal surfaces of porous solid by immersing enzyme‐free particles in a well mixed solution of enzyme. The ensuing impregnation process involves coupled transient mass transfer and surface attachment of enzyme. A mathematical model is employed to explore the influences of process parameters on the amount of enzyme loaded and the distribution of immobilized enzyme within the support particles. Nonuniform loading of the support occurs under some conditions. This is significant since the distribution of enzyme within the support particle influences the overall activity and stability of the immobilized enzyme catalyst. The model developed here may also be used to describe removal of reversibly immobilized enzyme during washing or utilization of the immobilized enzyme catalyst.