bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bacterial SCP from methanol in Kuwait: Product revovery and composition
Authors: Prokop A. , Ratcliffe H. D. , Fatayer M. I. , Al‐Awadhi N. , Khamis A. , Murad M. , Bond C. , Hamdan I. Y. 
Published: December 2004

AbstractThe rationale behind KISR's involvement in SCP is explained and emphasis towards the use of aerobic thermophilic/thermotolerant methanol‐utilizing bacterial cultures is stressed. An attempt is made to correlate different pilot plant harvesting procedures for biomass recovery with product quality. The latter is expressed as crude and true protein content, moisture and ash content, mineral composition of the ash, and amino acids profiles. The most suitable harvesting procedures were found to be those using a mild heat–acid or acid–heat treatment. Both of these procedures gave high recovery efficiencies and suitable product nutrition.
Some properties of a β‐galactosidase from an extremely thermophilic bacterium
Authors: Cowan D. A. , Daniel R. M. , Martin A. M. , Morgan H. W. 
Published: December 2004

AbstractAn inducible β‐galactosidase from an extremely thermophilic organism, Thermus strain 4−1A, has been isolated and partially purified. There were significant dissimilarities to T. aquaticus β‐galactosidase. It had a pl of 4.5, was inhibited by sulphydryl inhibitors and a number of transition metals, and was activated by EDTA and SH‐containing reagents. The β‐galactosidase showed strong product inhibition, and weaker inhibition by some other mono‐ and disaccharides. It was very stable up to 90°C at pH 8. On immobilization by diazonium linkage to porous glass, the pH optimum (6.0), the KM with ONPG (5mM) and the product inhibition were not altered.
Studies on on‐line bioreactor identification. III. Sensitivity problems with respiratory and heat evolution measurements
Authors: Grosz Ron , Stephanopoulos Gregory , San K. Y. 
Published: December 2004

AbstractThe applicability of the respiratory quotient measurement, a heat evolution measurement, and a commonly observed correlation between the respiratory quotient and product yield to on‐line bioreactor identification and control were inspected. It was found that singularities can exist in macroscopic balances used in connection with these measurements or the correlation, rendering them inappropriate for process parameter identification. By the formulation of generalized metabolic pathways together with NADH2 and ATP balances, general rules were derived for identifying conditions causing singularities. Thus it was found that, in addition to other less probable situations, the RQ measurement becomes impractical when the degree of reductance of the substrate is identical to that of the product, if any, and close to that of biomass. The correlation always presents sensitivity problems because it is nearly a linear combination of the elemental balances and the balance arising from the definition of the respiratory quotient. The heat evolution measurement nearly always presents sensitivity problems because of a linear dependence between the enthalpy balance and the degree of reductance, or NADH2, balance due to the regularity that the degrees of reductance of most biological compounds are proportional to their heats of combustion. Problems are considered and suggestions made for replacing the measurements, when inapplicable, or the correlation with an ATP balance. Experimental results and numerical studies on the fermentations of yeast and E. coli support the theoretically derived rules.
Kinetic studies of sepharose‐and CH‐sepharose‐immobilized dihydrofolate reductase
Authors: Ahmed Faizy , Dunlap R. Bruce 
Published: December 2004

AbstractDihydrofolate reductase, purified to homogeneity from amethopterin‐resistant Lactobacillus casei, was immobilized by coupling to cyanogen bromide‐activated Sepharose or carbodiimide‐activated CH‐Sepharose. Coupling yields were determined by amino acid analysis following the hydrolysis of the gel. Enzyme activity was measured by the conventional spectrophotometric procedure, thus permitting the facile characterization of the immobilized enzyme. The pH optimum of the immobilized enzyme was shifted to 5.8 compared with pH 5.5 for the soluble enzyme. The immobilized enzyme retained greater than 90%of the initial activity over a six‐month period and could be reused as many as ten times without loss of activity. As observed with the soluble enzyme, the activity of immobilized enzyme, which was lost on denaturation with 4M guanidine hydrochloride, was recovered rapidly and completely by washing the gel with buffer. The Kmapp values for dihydrofolate and NADPH for the immobilized enzyme were increased 15–164‐fold over the Km values measured for soluble dihydrofolate reductase. Scatchard analysis of the interaction of amethopterin with the immobilized enzyme yielded linear plots and a Kdapp value of 0.56 ×10−8M, and revealed that all of the immobilized enzyme molecules were capable of binding the ligand.
Activity of Pseudomonas aeruginosa in biofilms: Steady state
Authors: Bakke R. , Trulear M. G. , Robinson J. A. , Characklis W. G. 
Published: December 2004

AbstractAerobic glucose metabolism by Pseudomonas aeruginosa in steady‐state biofilms at various substrate loading rates and reactor dilution rates was investigated. Variables monitored were substrate (glucose), biofilm cellular density, biofilm extracellular polymeric substance (EPS) density, and suspended cellular and EPS concentrations. A mathematical model developed to describe the system was compared to experimental data. Intrinsic yield and rate coefficients included in the model were obtained from suspended continuous culture studies of glucose metabolism by P. aeruginosa. Experimental data compared well with the mathematical model, suggesting that P. aeruginosa does not behave differently in steady‐state biofilm cultures, where diffusional resistance is negligible, than in suspended cultures. This implies that kinetic and stoichiometric coefficients for P. aeruginosa derived in suspended continuous culture can be used to describe steady‐state biofilm processes.
Solid substrate fermentation of wheat straw to fungal protein
Authors: Laukevics J. J. , Apsite A. F. , Viesturs U. E. , Tengerdy R. P. 
Published: December 2004

AbstractSteam‐treated wheat straw at a 70% (w/w) moisture level was subjected to solid substrate fermentation (SSF) with Trichoderma reesei (Riga, USSR) or a mixed culture of T. reesei and Endomycopsis fibuliger (R‐574) in fermentation equipment of various design: some with mixing, some with stationary layers, including a mixedlayer 1.5‐m3 pilot plant scale fermenter. The best protein productivity was obtained in stationary layer fermenters with a product containing 13% protein. The main limitations of lignocellulose SSF, such as hindrance of fungal growth, limiting accessibility and availability of substrate, and difficulty in moisture and heat control, were analyzed. The technological parameters of SSF, submerged fermentation, and alternate lignocellulose conversion processes were compared. The SSF had lower overall efficiency but higher product concentration per reaction volume than other conversion schemes.
A simplified calculation method applied to enzyme inactivation during drying
Authors: Liou J. K. , Luyben K. Ch. A. M. , Bruin S. 
Published: December 2004

AbstractAn approximate method for solving the nonlinear diffusion problem in the case of a power‐function variation of the diffusion coefficient with concentration has been applied to a drying process with simultaneous enzyme inactivation. Experimental results obtained by air drying of soybean lipoxygenase entrapped in a glucose calcium‐alginate gel are in good agreement with the predicted behavior, whereas hardly any differences occur between the results obtained with the approximate method and those obtained by a numerical solution of the original model.
Sand administration as an instrument for biofilm control of Pseudomonas putida ATCC 11172 in chemostat cultures
Authors: Molin Göran , Nilsson Inge 
Published: December 2004

AbstractPseudomonas putida ATCC 11172 was grown in chemostat on L‐asparagine or phenol as the sole, limiting carbon and energy source. The growth characteristics of a culture where a biofilm was present, were compared with one where the biofilm was strongly reduced by the grinding and shearing effect of sand suspended in the culture. In the presence of the intact biofilm, the curve of steady‐state biomass versus dilution rate diverged greatly from the theoretical pattern predicted by conventional chemostat models. The sand strongly retarded the biofilm formation and to a high degree restored the shape of the biomass versus dilution rate curve to a more conventional pattern. The maximum specific growth rate (μmax) could not be calculated from the biofilm cultures. However using the sand cultures, μmax was determined to 0.64 h−1 with L‐asparagine as the carbon source and 0.49 h−1 with phenol which compare favorably with the respective μmax values calculated from batch cultures.Incorporation of sand into strongly agitated cultures is recommended as an efficient and simple means of controlling biofilm formation in continuous cultures. The method may enable the gathering of basic kinetic data difficult to obtain in the presence of biofilm.
Utilization of short chain monocarboxylic acids in an effluent of a petrochemical industry by Acinetobacter calcoaceticus
Authors: Du Preez J. C. , Lategan P. M. , Toerien D. F. 
Published: December 2004

AbstractThe aqueous effluent generated by the Fischer‐‐Tropsch process, containing a total of 13 g/L C2–C5 monocarboxylic acids, was investigated as a potential substrate for the production of single‐cell protein (SCP). A bacterial isolate, Acinetobacter calcoaceticus, could utilize all the acids in the effluent simultaneously in chemostat cultures, and no residual acids were detected in the culture below a dilution rate of 0.78 h−1. The critical dilution rate was 1.04 h−1. The maintenance energy requirement of the cells growing on the monocarboxylic acid mixture was considerably lower than that of cells growing on acetate as the sole carbon source. Enrichment of the effluent with ethanol to increase the biomass concentration was successful and still allowed the simultaneous and efficient utilization of all the carbon sources, but resulted in a decrease of the critical dilution rate by ca. 20%.
Direct measurement of carbon substrate oxidation and incorporation patterns in RuMP‐type methylotrophs: Chemostatic cultures of Methylomonas L3
Authors: Chu I‐Ming , Bussineau Christopher M. , Papoutsakis Eleftherios Terry 
Published: December 2004

AbstractA technique using C‐14 isotope tracers to probe the branching of carbon flow in methylotrophic bacteria has been devised and applied to continuous steady‐state cultures. Methylomonas L3, a strain which utilizes the KDPG/TA variant of the ribulose monophosphate cycle for carbon fixation, was employed in the experimental studies. The actual in vivo rates of substrate‐carbon incorporation into biomass, both direct and via CO2, and of the two carbon oxidation schemes were determined in three different steady‐state cultures. The results show that the carbon substrate is oxidized predominantly via formate (the linear oxidation scheme), and that the cyclic scheme of oxidation is minimally, if at all, utilized. The carbon incorporation and oxidation patterns appear to vary considerably with the dilution rate and the inoculum history. The experimental accuracy of the new technique is discussed in detail.
Potentiometric system for selective formate measurement and improvement of response characteristics by permeation of cells
Authors: Ho May Y. K. , Rechnitz G. A. 
Published: December 2004

AbstractA formate‐selective biocatalytic potentiometric electrode system based on whole cells Pseudomonas oxalaticus has been developed. Permeation of the Gram‐negative Pseudomonas oxalaticus microbial cells by EDTA is shown to improve the response slope from 38 mV/decade to 49 mV/decade, resulting in increased sensitivity. Out of 13 possibly interfering compounds tested, only pyruvate and lactate showed moderate response.
Effects of recombinant plasmid content on growth properties and cloned gene product formation in Escherichia coli
Authors: Seo Jin‐Ho , Bailey James E. 
Published: December 2004

AbstractPlasmid–host cell interactions have been investigated experimentally using Escherichia coli HB101, plasmid RSF1050 which contains the origin of replication of pMB1, and four other closely related copy number mutant plasmids. Growth characteristics of these recombinant strains and β‐lactamase activity expressed from a plasmid gene were investigated in Luria broth (LB) and in minimal medium (M9) containing in some cases casamino acids or different concentrations of α‐methylglucoside, a competitive inhibitor of glucose transport. Maximum specific growth rates in LB and minimal media were reduced for increasing plasmid content per cell. Plasmid copy number increased when specific growth rate was reduced by changing medium composition. Growth rates of high copy number strains were less sensitive to α‐methylglucoside than lower copy number strains and the plasmidfree host. The overall efficiency of plasmid gene expression, measured as the ratio of β‐lactamase specific activity to plasmid content, decreased significantly with increasing plasmid content in LB medium.
Immobilization of enzyme onto poly(ethylene–vinyl alcohol) membrane
Authors: Imai Kiyokazu , Shiomi Tomoo , Uchida Kozo , Miya Masamitsu 
Published: December 2004

AbstractInvertase was ionically bound to the poly(ethylene–vinyl alcohol) membrane surface modified with two aminoacetals with different molecular length, 2‐dimethyl‐aminoacetoaldehyde dimethylacetal (AAA) and 3‐(N, N‐dimethylamino‐n‐propanediamine) propionaldehyde dimethylacetal (APA). Immobilization conditions were determined with respect to enzyme concentration in solution, pH value, ionic strength in immobilization solution, and immobilization time. Various properties of immobilized invertase were evaluated, and thermal stability was found especially to be improved by immobilization. The apparent Michaelis constant, Km, was smaller for invertase bound by APA with longer molecular lengths than for invertase bound by AAA. We attempted to bind glucoamylase of Rhizopus delemar origin in the same way. The amount and activity of immobilized glucoamylase were much less than of invertase.
Effect of amino acid supplement on cell yield and gene product in Escherichia coli harboring plasmid
Authors: Mizutani Satoru , Mori Hironori , Shimizu Shoichi , Sakaguchi Kenji , Kobayashi Takeshi 
Published: December 2004

AbstractEscherichia coli harboring a recombinant plasmid was cultivated in fed‐batch culture to enhance production of a gene product. Expression of the leucine gene from Thermus thermophilus in the recombinant plasmid was examined by the assay of β‐isopropylmalate dehydrogenase activity at 75°C. When E. coli was cultivated in medium without leucine, biomass concentration reached 15 g/L and the specific activity became 0.082 U/mg protein. When leucine was fed in the medium throughout cultivation, although biomass concentration reached 63 g/L, the specific activity decreased to 0.016 U/mg protein. When E. coli was cultivated in medium containing 1 g leucine/L, the specific activity remained virtually constant (about 0.13 U/mg protein) and biomass concentration reached 32 g dry cells/L. In these cultivations, growth yields of several amino acids and glucose were examined. When leucine was not added to the medium, growth yields except for histidine were lowest. When leucine was fed throughout the cultivation, growth yields of glucose and tryptophan were highest. The pH‐stat was useful for feeding amino acids.
Adsorption equilibrium in immuno‐affinity chromatography with polyclonal and monoclonal antibodies
Authors: Sada Eizo , Katoh Shigeo , Sukai Kiyoshi , Tohma Masaaki , Kondo Akihiko 
Published: December 2004

AbstractThe effects of pH, ionic strength, anion species, and antibody concentration on the adsorption equilibrium between immobilized antibodies and antigens were studied by use of anti‐BSA, anti‐HSA, anti‐BlgG, and monoclonal anti‐HSA coupled to Sepharose 4B. The polyclonal antibodies possessed average binding affinities of the order of 108M−1, and the heterogeneity was accounted for by assuming a normal distribution of the free energy of antibody–antigen combination. The monoclonal antibody, on the other hand, showed a homogeneous affinity of the Langmuir type. Bound antigens could be eluted by lowering pH or adding a chaotropic anion, and their purity was very high. The antibody ligand was sufficiently stable for repeated use.
Enzymatic saccharification of pretreated rice straw and biomass production
Authors: Araujo A. , D'Souza J. 
Published: December 2004

AbstractA comparative study on the saccharification of pretreated rice straw was brought about by using cellulase enzyme produced by Aspergillus terreus ATCC 52430 and its mutant strain UNGI‐40. The effect of enzyme and substrate concentrations on the saccharification rate at 24 and 48 were studied. A syrup with 7% sugar concentration was obtained with a 10% substrate concentration for the mutant case, whereas a syrup with 6.8% sugar concentration was obtained with 3.5 times concentrated enzyme from the wild strain. A high saccharification value was obtained with low substrate concentration; the higher the substrate concentration used, the lower the percent saccharification. The glucose content in the hydrolysate comprised 80–82% of total reducing sugars; the remainder was cellobiose and xylose together. The hydrolysate supported the growth of yeasts Candida utilis and Saccharomyces cerevisiae ATCC 52431. A biomass with a 48% protein content was obtained. The essential amino acid composition of yeast biomass was determined.
An immobilized enzyme reactor for the detoxification of bilirubin
Authors: Sung Cynthia , Lavin Arthur , Klibanov Alexander M. , Langer Robert 
Published: December 2004

AbstractAn immobilized enzyme reactor has been developed for the degradation of bilirubin as a potential treatment for neonatal jaundice. It utilizes the enzyme bilirubin oxidase from Myrothecium verrucaria, which in the presence of molecular oxygen converts bilirubin to biliverdin and other products that are much less toxic than bilirubin. Bilirubin oxidase was covalently attached to agarose beads using cyano transfer activation. Forty percent of the specific activity of bilirubin oxidase was retained after immmobilization, and preparations with 20 units of enzymatic activity per gram of drained wet weight of gel were obtained. The stability of bilirubin oxidase at pH 7.4 and 37°C was improved fivefold by immobilization. A 15‐mL column containing immobilized bilirubin oxidase, through which a 37°C solution of 332μM bilirubin and 450μM human serum albumin in 0.05M phosphate buffer (pH 7.4) was passed at 1 mL/min, converted more than 60 percent of the bilirubin per pass. The substrate specificity of the enzyme and the small volume of the reactor are important characteristics for this clinical application where it is desirable to remove only one compound from the blood and to minimize the volume of blood in the extracorporeal circuit. This reactor, by detoxifying the jaundiced infant's blood of bilirubin, would eliminate the risks associated with the use of donor blood as is done currently in treating severe neonatal jaundice.
Simultaneous utilization of methanol–glucose mixtures by Hansenula polymorpha in chemostat: Influence of dilution rate and mixture composition on utilization pattern
Authors: Egli Thomas , Bosshard Christoph , Hamer Geoffrey 
Published: December 2004

AbstractThe utilization of mixtures of methanol (C1) and glucose (C6) of different composition by the methylotrophic yeast Hansenula polymorpha was studied in carbon‐limited chemostat culture. For all mixtures tested a similar utilization pattern was observed: At low dilution rates both carbon sources were utilized simultaneously, but at high dilution rates the cells used glucose only and the unutilized methanol accumulated in the culture medium. When grown with C1 only, the cells exhibited a critical dilution rate Dc(C1) of 0.19 h−1, but when C1–C6 mixtures were used as the carbon and energy substrate, the yeast was able to completely utilize C1 at dilution rates considerably higher than Dc(C1). The dilution rate at which the transition from C1–C6 growth to C6 growth occurred (Dt) was strictly dependent on the composition of the C1–C6 mixture in the feed, and Dt increased with decreasing proportions of C1 in the mixture. During mixed substrate growth the formation of biomass from the two substrates was additive. The results reported indicate that the utilization of C1–C6 mixtures and hence Dt in H. polymorpha are subject to two different regulatory regimes. When the cells were growing with C1–C6 mixtures containing more than 60% C1, the transition form C1–C6 to C6 growth was most probably influenced by the maximum C1 oxidizing capacity of the cells, whereas for growth with mixtures containing less than 40% C1, a growth rate of 0.28–0.30 h−1 seemed to be the limiting barrier for the simultaneous utilization of the components of the binary carbon and energy substrate mixture.
Enhancement of growth and ferrous iron oxidation rates of T. Ferrooxidans by electrochemical reduction of ferric iron
Authors: Yunker S. B. , Radovich J. M. 
Published: December 2004

AbstractThiobacillus ferrooxidans, the bacterium most widely used; in bioleaching or microbial desulfurization studies, was grown in an electrolytic bioreactor containing a synthetic, ferrous sulfate medium. Passage of current through the medium reduced the bacterially generated ferric iron to the ferrous iron substrate. When used in conjunction with an inoculum that had been adapted to the electrolytic growth conditions, this technique increased the protein (cell) concentration by 3.7 times, increased the protein (cell) production rate by 6.5 times, increased the yield coefficient (cellular efficiency) by 8.0 times, and increased the ferrous iron oxidation rate by 1.5 times at 29°C, compared with conventional cultivation techniques. A Monod‐type equation with accepted values for the maximum specific growth rate could not account for the increased growth rate under electrolytic conditions.
Invertase immobilized on macroporous polystyrene: Properties and kinetic characterization
Authors: Mansfeld J. , Schellenberger A. 
Published: December 2004

AbstractInvertase from baker's yeast (Saccharomyces cerevisiae) was covalently bound via benzoquinone and glutaraldehyde to a macroporous polystyrene anion exchanger. The behavior of the invertase–polystyrene complexes in batch and packed‐bed reactors was characterized kinetically. In addition to kinetic studies on sucrose hydrolysis at low initial substrate concentrations, the dependence of conversion degree on flow rate at high, industrially used substrate concentrations was determined. The described invertase–polystyrene complexes are suitable for technical application in the production of glucose–fructose mixtures because of their high specific and relative activities, as well as the good hydrodynamical and mechanical properties of the polystyrene matrix.
Effects of dissolved oxygen shock on the stability of recombinant Escherichia coli containing plasmid pKN401
Authors: Hopkins David J. , Betenbaugh Michael J. , Dhurjati Prasad 
Published: December 2004

AbstractThe effect of dissolved oxygen shock on the stability of recombinant Escherichia coli cells containing plasmid pKN401 was investigated. The recombinant cells were stable in control batch experiments in media with and without ampicillin. However, these recombinant cells were highly unstable under conditions where a dissolved oxygen shock was induced. The results have implications for design of aerated reactors for recombinant cells.