bluuebunny/crossref_metadata_2025_split huggingface dataset:
The continuously fed batch reactor for measuring microbial growth rates
Authors: Webster Ian A. 
Published: December 2004

AbstractThe contiuously fed batch reactor (CFBR) is proposed as an alternative technique to the traditional chemostat and batch cultures, for measuring microbial growth rates. After reviewing the pitfalls which plague the conventional growth measurement techniques, the methodology for operating the CFBR to generate specific growth‐rate‐versus‐substrate‐concentration data is detailed. This information is extracted from the transient state of the CFBR where both the biomass and substrate concentration show extrema in time. It is suggested that the CFBR can be used for measuring microbial growth rates at low rates at low substrate concentrations where the chemostat method normally encounters difficulties.
Determination of inorganic phosphorus using immobilized pyruvate oxidase
Authors: Tabata Masayoshi , Murachi Takashi 
Published: December 2004

AbstractA new method for the automated analysis of inorganic phosphorus using immobilized enzyme was established. The method was based on the determination of hydrogen peroxide formed by the action of pyruvate oxidase on inorganic phosphate and pyruvate. Since pyruvate oxidase required inorganic phosphate for its stability and therefore had to be kept in a buffer containing inorganic phosphate, it could hardly be used as a reagent in the form of aqueous solution for the determination of inorganic phosphorus. This difficulty was overcome by using immobilized pyruvate oxidase in column form. When the present method was applied to the determination of inorganic phosphorus in serum, it gave perfect linearity of the data up to 0.20 g inorganic phosphorus/L with satisfactory precision, reproducibility, high sensitivity, and accurate recoveries. The immobilized enzyme reactor unit showed enhanced heat stability and good operational stability for a one‐month period, during which time it was used over 900 times for analyses. The enzyme column was not affected by organic phosphorus compounds. The results correlated satisfactorily with those obtained by another well‐established method.
Isoelectric precipitation of soy protein. II. Kinetics of protein aggregate growth and breakage
Authors: Petenate Angela M. , Glatz Charles E. 
Published: December 2004

AbstractProtein aggregate growth and breakage in agitated suspensions are modeled. The model includes growth of particles by a turbulent collision mechanism and breakage by a hydrodynamic shear mechanism. In the model, breakage results in the splitting of the particles into several small fragments. The model parameters are a growth rate constant and a breakage rate constant. Aggregate size distributions were measured with a Coulter counter and the data interpreted using a population balance that governs the steady‐state particle size distribution in a continuous stirred tank reactor. Effects of changes in the operating variables pH, concentration, mean residence time, ionic strength, and mixing power input on the model kinetic parameters are investigated.
Collagen strip with immobilized luciferase for ATP bioluminescent determination
Authors: Blum Loïc J. , Coulet Pierre R. , Gautheron Daniéle C. 
Published: December 2004

AbstractFirefly luciferase from Photinus pyralis has been covalently bound to a collagen strip via an acylazide activation process. Immobilization performed in the presence of both substrates ATP and luciferin allows to increase the activity retained on the strip. The best activity exhibited by immobilized luciferase was obtained in a 0.05M Tris‐acetate buffer, pH 7.75. The pH optimum and the activation energy of luciferase have been found unchanged after immobilization. In the chosen stirring conditions, no diffusional limitations of substrates appear. ATP measurements can be performed with collagen‐bound luciferase in the range 1.10−11 M−3.10−6 M. It was possible to store the strips at 4°C in a dehydrated form; then, the bound enzyme retains 20% of its initial activity after eight months. Human blood ATP was measured with this collagen‐bound luciferase and the results were found in good agreement with those obtained by soluble luciferase.
Alkaline treatment of wheat straw for increasing anaerobic biodegradability
Authors: Pavlostathis Spyros G. , Gossett James M. 
Published: December 2004

AbstractWheat straw was treated with NaOH and anaerobically digested for methane production. Alkaline treatment resulted in a greater than 100% increase in biodegradability of wheat straw. The potential of a process flow scheme employing high alkali concentration at ambient temperature with solids separation and recycle of filtrate containing residual alkali was explored. The effect of NaOH on the solubilization of cell wall constituents and potential problems of toxicity are discussed. A solubilization model was developed which is used to predict biodegradability of whole samples based on solids and filtrate biodegradabilities. Energy requirements and chemical costs are also addressed.
Dilute acid hydrolysis of paper birch: Kinetics studies of xylan and acetyl‐group hydrolysis
Authors: Maloney Mark T. , Chapman Thomas W. , Baker Andrew J. 
Published: December 2004

AbstractBatch hydrolysis kinetics of paper birch (Betula papyrifera) xylan and its associated acetyl groups in dilute sulfuric acid have been measured for acid concentrations of between 0.04 and 0.18M and temperatures of between 100 and 170°C. Only 5% of the cellulose was hydrolyzed for up to 85% xylan removal. Rate data were correlated well by a parallel reaction model based on the existence of reactive and resistant xylan portions. The resulting rate equation predicts the experimental xylan concentrations in the residue to within 10%. Hydrolysis of xylan‐associated acetyl groups was found to occur at the same rate as that of xylan, except at 100°C, where acetyl is released preferentially. No effect of acid concentration on the rate of acetyl removal relative to that of xylan was evident.
A microbial culture with oxygen‐sensitive product distribution as a potential tool for characterizing bioreactor oxygen transport
Authors: Moes J. , Griot M. , Keller J. , Heinzle E. , Dunn I. J. , Bourne J. R. 
Published: December 2004

AbstractThe dissolved oxygen (DO) level has been shown to have a profound effect on the product distribution of a Bacillus subtilis culture, with acetoin being excreted with DO above 100 parts per billion (ppb) and butanediol below 100 ppb. The product concentration ratio changed rapidly in the 80–90 ppb range. Switching from one oxygen level to another caused one already accumulated product to be converted to the other in a reversible manner. Rates of change of 0.5–1 g/L h enabled detection within 10 min. Detection sensitivity is enhanced because the ratio of two concentrations can be measured. Remarkably sensitive to mixing rates, the culture responded to changes in stirring speed during experiments in which the dissolved oxygen was controlled at a constant level with a novel control system. Thus, the culture is capable of detecting dead zones in relatively well‐mixed reactors and oxygen gradients in column and tubular reactors. High‐viscosity effects can also be investigated since the culture grows well in xanthan gum solutions. Preliminary kinetic model development indicates that a useful model for simulating reactor mixing and transport effects can be developed to aid in the planning of experiments.
A Multispecies model of biological treatment with sequential pollutant oxidation
Authors: Vasiliev V. B. , Vavilin V. A. 
Published: December 2004

AbstractThe multispecies biological treatment model including the consequent substrates consumption is suggested. The model describes the adaptation in the distribution of species that are included in the composition of activated sludge. It was shown that the effects of adaptation are similar for the consequent as well as simultaneous mechanisms of substrate oxidation.
Purification and characterization of endo‐xylanases from Aspergillus niger. I. Two isozymes active on xylan backbones near branch points
Authors: Frederick Mary M. , Kiang Chih‐Hen , Frederick James R. , Reilly Peter J. 
Published: December 2004

AbstractTwo endo‐xylanases (1,4‐β‐D‐xylan xylanohydrolase, EC 3.2.1.8) were purified to homogeneity from a crude Aspergillus niger pentosanase preparation by Ultrogel AcA 54 gel permeation chromatography, SP‐Sephadex C‐25 cation exchange chromatography at pH 4.5, Sephadex G‐50 gel permeation chromatography, and a second SP‐Sephadex C‐25 step, this one at pH 5.8. The two xylanases hydrolyzed soluble xylan more rapidly than insoluble branched xylan, but attacked each substance to an equal extent. Their low activity on a linear xylooligosaccharide mixture and absence of activity on insoluble xylan freed of branches suggest that the xylanases require a branch point nearby for significant attack. No xylose or L‐arabinose was produced, the major products of low molecular weight being tri‐ and pentasaccharides and smaller amounts of di‐, tetra‐, and hexasaccharides. There was low activity on untreated and crystalline cellulose and on carboxymethylcellulose and no activity on other polysaccharides tested. These two xylanases had molecular weights of ca. 1.3 × 104 and similar amino acid profiles, high in acidic and low in sulfur‐containing residues. Isoelectric points were 8.6 for I and 9.0 for II. Optimum pH values for activity were 6.0 and 5.5, respectively. In a 20‐min assay at pH 5.5, each was most active at 45°C, with activation energies up to 40°C of 30.4 and 38.8 kJ/ mol, respectively. Optimum pH levels for stability were 5.0 and 6.0, with half‐lives at 60°C and those pHs of 20 and 75 min, respectively.
Continuous production of ethanol from fructose by immobilized growing cells of Zymomonas mobilis
Authors: Jain W. K. , Toran‐Diaz I. , Baratti J. 
Published: December 2004

AbstractImmobilized growing cells of Zymomonas mobilis were found to ferment rapidly and efficiently media containing 100 g/L fructose in a continuous reactor. A volumetric ethanol productivity of 94.8 g/L h was achieved at a substrate conversion of 75.5%. With 97% conversion of substrate the productivity was 28.4 g/L h. At fructose concentrations of 150 and 200 g/L substrate and product inhibitions limited the performance of the reactor. Ethanol production was constant over a period of 55 days.
Carboxypeptidase a immobilization on activated styrene–maleic anhydride systems
Authors: Dua R. D. , Kumar Sanjay , Vasudevan Padma 
Published: December 2004

AbstractThe copolymer styrene–maleic anhydride (SMA) was activated to various forms to create enzyme coupling groups. Carboxypeptidase A (CPA) was Immobilized on these supports to enhance their thermal and chemical stability. Immobilized enzyme retained 60–70% of the original activity. When kept at 60°C, while free enzyme was deactivated within 30 min, the immobilized enzyme retained 40% of initial activity at the end of 3 h. The half‐life of free enzyme was only 21 min, while for immobilized enzyme it was enhanced up to 3 h. Also, the immobilized enzyme could be repeatedly used over 50 times retaining almost 50% of original activity.
Effects of temperature and dilution rate on the copy number of recombinant plasmid in continuous culture of Bacillus stearothermophilus (pLP11)
Authors: Koizumi Jun‐ichi , Monden Yoshiaki , Aiba Shuichi 
Published: December 2004

AbstractThe penicillinase yield YP/X (U/g cell) of a transformant Bacillus stearothermophilus CU21 (pLP11) in continuous culture of LGP broth at 44, 47.5, and 50°C, respectively, depended not only on temperature, θ (°C), but also on dilution rate, D (h−1), in a peculiar fashion that could not have been realized if the product were from the gene on the chromosome rather than the plasmid. The gene dosage effect could account for the unusual dependence of YP/X on θ and D, because the mode of YP/X as a function of D at a given temperature resembled that of plasmid content Cp (mg plasmid/g cell) vs. D at the same temperature. In other words, Cp, corresponding to the copy number of plasmid per grams of cell, could be controlled by either θ, D, or both in this instance. However, when the gene expression efficiency, ε (U/ng plasmid), was plotted versus Cp, the effects of θ and D on the expression became indistinct.
Kinetics of chitinase production. II. Relationship between bacterial growth, chitin hydrolysis and enzyme synthesis
Authors: Young Manuel E. , Bell Richard L. , Carroad Paul A. 
Published: December 2004

AbstractA comprehensive model for chitinase production during growth of Serratia marcescens QMB 1466 on chitin was developed taking into account the rate of chitin hydrolysis in order to estimate the rate of bacterial growth. In relating growth with enzyme synthesis the total enzyme concentration was used as the sum of the enzyme present in the bulk of the fermentation broth and the enzyme adsorbed on the chitin particles. The equations constituting the proposed model were fitted to the experimental results from both continuous and batch fermentation to obtain parameters describing substrate yield, metabolic maintenance, and enzyme yields.
β‐Glucosidase of Penicillium funiculosum. I. Purification
Authors: Kantham Lakshmi , Vartak H. G. , Jagannathan V. 
Published: December 2004

AbstractA strain of Penicillium funiculosum, isolated in this laboratory, produced in high yield both endo‐ and exo‐glucanases and β‐glucosidases, which were suitable for the saccharification of cellulosic materials. The isolation of the β‐glucosidase of this organism, which differs from other β‐glucosidases of fungi in its substrate specificity, by preparative electrophoresis, is described in this article. The organism was grown on a lactose‐casein medium and the culture filtrate concentrated by ammonium sulfate precipitation and dialysis. Electrophoresis was carried out on large slabs of polyacrylamide gel in an anodicrun in the presence of borate at pH 7. After elution of active fractions, a cathodic run was made at pH 6.0. Two precipitations with ammonium sulfate resulted in a homogeneous enzyme (specific activity 174 IU/mg). A second isozyme was also produced by P. funiculosum on cellulose‐wheat bran medium. This isozyme was purified by electrophoresis at pH 7.0 in the absence of borate and was obtained free from other isozymes of β‐glucosidase and cellulases.
β‐Glucosidase of Penicillium funiculosum. II. Properties and mycelial binding
Authors: Kantham Lakshmi , Jagannathan V. 
Published: December 2004

AbstractThe properties of two isozymes of β‐glucosidase of Penicillium funiculosum (part I of this series) are described. The molecular weights of isozyme 1 was 2.3 × 105 by gel filtration and 1.2 × 105 by SDS gel electrophoresis, indicating two subunits. The molecular weight of isozyme 2 was unusually low for a fungal β‐glucosidase: 1.6 × 104 by gel filtration and 3.7 × 104 in the presence of isopropanol. The two enzymes differed from other fungal β‐glucosidases in their substrate specificities. They showed high activity with pNPG, cellobiose, cellotriose, cellotetraose, cellopentaose, gentiobiose, and laminarin, but were inactive with filter paper, CM cellulose, or derivatives or stabilized by bovine serum albumin and several alcohols such as butanol and propanol. It was inhibited by glucono‐δ‐lactone (Ki = 0.67μM) and glucose (Ki = 0.92mM).The enzyme was quantitatively adsorbed by P. funiculosum mycelium at pH 4 and the immobilized enzyme was as enzymically active as the free enzyme, but more heat stable. The binding efficiency was very high (5000 IU enzyme/g mycelium). It could be quantitatively eluted with buffers at pH 7 or by 0.02M Ca, Mg, or Al chlorides. The binding was selective, since mycelium grown on lactose could produce and also bind only β‐glucosidase isozyme 1, whereas mycelium grown on cellulose could produce as well as bind both β‐glucosidase isozymes as well as cellulases. Mycelial binding was unaffected by washing with EDTA or trypsinization, but was totally lost by washing with dilute KOH, HCl, or ethylenediamine.
The dependence of protein release from Bacillus amyloliquefaciens on the growth phase in batch culture
Authors: Cumming R. H. , Tuffnell J. , Street G. 
Published: December 2004

AbstractFor the recovery of intracellular material from bacteria it is often necessary to disrupt the cells. Much work has been done on the kinetics of protein release in beadmills,1 homogenizers,2 and by ultrasonication.3 In this paper we report how the growth phase of Bacillus amyloliquefaciens grown in batch culture affects the rate of protein release by ball milling, ultrasonication, and autolysis. We further suggest that autolysis is a feasible method for disrupting Bacillus.
Comparison between immobilized Kluyveromyces fragilis and Saccharomyces cerevisiae coimmobilized with β‐galactosidase, with respect to continuous ethanol production from concentrated whey permeate
Authors: Hahn‐Hägerdal B. 
Published: December 2004

AbstractKluyveromyces fragilis immobilized in calcium alginate gel was compared to Saccharomyces cerevisiae coimmobilized with β‐galactosidase, for continuous ethanol production from whey permeate in packed‐bed‐type columns. Four different whey concentrations were studied, equivalent to 4.5, 10, 15, and 20% lactose, respectively. In all cases the coimmobilized preparation produced more ethanol than K. fragilis. The study went on for more than 5 weeks. K. fragilis showed a decline in activity after 20 days, while the coimmobilized preparation was stableduring the entrire investigation. Under experimental conditions theoretical yields of ethanol were obtained from 4.5 and 10% lactose substrates with the coimmobilized system. Using 15% lactose substrate, theoretical yields were only obtained when a galactose‐adapted immobilized S. cerevisiae column was run in series with the coimmobilized column. Then a maximum of 71 g/L ethanol was produced with a productivity of 2.5 g/L h. The coimmobilized column alone gave a maximum ethanol concentration of 52 g/L with a productivity of 4.5 g/L h, whereas immobolized K. fragilis only produced 13 g/L ethanol with a productivity of 1.1 g/L h. It was not possible to obtain theoretical yields of ethanol from the highest substrate concentration.
Conversion of cellulose to sugars by resting cells of a mesophilic anaerobe, Bacteriodes cellulosolvens
Authors: Giuliano Christine , Khan A. W. 
Published: December 2004

AbstractDuring the growth of Bacteroides cellulosolvens in media containing cellulose, the accumulation of unutilized sugars in the culture broth occurred mainly during the stationary phase of growth. Cells harvested during the stationary phase of growth continued to convert both cellulose and hemicellulose to cellobiose, glucose, and xylose. These three sugars caused feedback inhibition. Continuous removal of these sugars during the incubation of cells with cellulose at pH 5 accumulated ca. 32 g/L of sugars as compared to ca. 17 g/ produced under batch conditions of growth. Sugar formation by resting cells also increased with increasing cell concentration and did not require any nutrient.
Dual aerobic hollow‐fiber bioreactor for cultivation of Streptomyces aureofaciens
Authors: Robertson Channing R. , Kim In Ho 
Published: December 2004

AbstractStreptomyces aureofaciens (ATCC 12416c) was grown in the interstitial region formed by a parallel arrangement of three hollow silicone tubules contained within a microporous polypropylene hollow fiber. Liquid‐soluble nutrients were supplied by diffusion across the polypropylene fiber to the interstitial cell‐containing region whereas air or oxygen was provided by diffusion from the silicone tubule lumina to the cell mass. In this bioreactor, S. aureofaciens grew to high cell densities (greater than 1011 cells/cm3) and the culture so‐obtained continously synthesized the secondary metabolite tetracycline. The volumetric productivity of tetracycline based on the interstitial volume was 90 μg/ml/h and based on the total reactor volume was 5.5 μg/mL/h. The high surface area‐to‐volume ratio afforded by the cylindrical configuration together with spatially distinct conduits to continuously transport liquids and gases, each of which may be nutrients or products of biosynthesis, to or from a tissuelike cell mass provides an alternative to the conventional air‐ or oxygen‐sparged fermentation vessel. High volumetric reactor productivities may be achieved by virute of the concentrated stationary cell mass and by the appropriate selection of fiber sizes and materials so as to ensure adequate supplies of liquid and gaseous substrates to, as well as removal of metabolites from, most cells in the culture. This reactor topology is quite general and may be adapted to most microbial as well as mammalian and plant cell systems.
Simulation of CFSTR through development of a mathematical model for anaerobic growth of Escherichia coli cell population
Authors: Ataai M. M. , Shuler M. L. 
Published: December 2004

AbstractA computer model is described that simulates a population of Escherichia coli B/r‐A cells growing under anaerobic conditions. This population model is an ensemble of single‐cell models. The ability of the model of predict the dynamic response of a cell population in a CFSTR to a change in feed flowrates or concentrations was investigated. With glucose as the limiting nutrient the feed concentration of glucose was shifted from 1.0 to 1.88 g/L. With a fixed concentration of glucose (1.0 g/L) step changes in residence time (4.1–1.95 h) were examined. The predicted changes of cell size distribution, substrate concentration, RNA content, and cell dry weight during the transition period compared reasonably well to those observed experiementally. We believe this model is the only model currently available that can make such predictions on an a priori basis.
A kinetic study of Saccharomyces strains: Performance at high sugar concentrations
Authors: Converti Attilio , Perego Patrizia , Lodi Alessandra , Parisi Federico , del Borghi Marco 
Published: December 2004

AbstractAlcoholic fermentation represents a significant example of production of compounds utilizable as alternative energy sources. High ethanol concentration in the fermented wort is needed in order to reduce the energy consumption in the process of alcohol recovery. A particular Saccharomyces strain, of the oviformis species, obtained from fermented worts exhibiting high ethanol concentrations is studied and compared with a common S. cerevisiae strain in order to show its skill in fermenting very concentrated sugar solutions with an energy saving of ca. 10%.
Fuzzy bioengineering models
Authors: Dohnal Mirko 
Published: December 2004

AbstractA classical quantitative (analytical and/or statistical) analysis is not appropriate for some ill‐defined and/or very complex bioengineering problems. Therefore, a new form of analysis using fuzzy mathematics has been developed. The fuzzy model can utilize semiqualitative and linguistic data which are to a certain level inconsistent. Bioengineering interpretation of the basic concept of fuzzy mathematics is given together with a numerical algorithm for a fuzzy evaluation of a model. A simple fuzzy model of a fermentor is studied in detail.