bluuebunny/crossref_metadata_2025_split huggingface dataset:
Continuous culture in combined backmix–plug‐flow–tubular‐loop fermentor configurations
Authors: Toda K. , Dunn I. J. 
Published: December 2004

AbstractSeveral combinations of backmix, tubular‐loop, and plug‐flow fermentors with and without culture recycle were studied by computer simulations. The steady‐state concentrations of cell mass in a continuous culture were calculated as a function of dilution rate using Monod growth kinetics. It was found theoretically and verified for one case experimentally that the maximum dilution rate, over which microbial cells were washed out from the fermentor, could be elevated well beyond the maximum specific growth rate if a particular fermentor combination was used. A combination of two backmix fermentors has been analyzed previously by Sinclair and Brown. Application of this type of fermentor combination as a seed tank for performing continuous culture of microbes in a plug‐flow reactor was shown with special reference to fermentation production using the kinetics proposed by Luedeking and Piret, van Dedem and Moo‐Young, and Brown and Vass.
Production of alcohol from Jerusalem artichokes by yeasts
Authors: Duvnjak Z. , Kosaric N. , Kliza S. , Hayes D. 
Published: December 2004

AbstractVarious yeasts such as several strains of Saccharomyces diastaticus, S. cerevisiae, and Kluyveromyces fregilis were investigated for their ability to ferment the carbohydrates from Jerusalem artichokes to alcohol. Juice extracted of the carbohydrates. Fermentation was also carried out with raw artichokes without prior juice extraction. Result indicate that this row material has good potential for fuel alcohol production by fermentation.
Extracellular microbial polysaccharides: Generalized power law for biopolysaccharide solutions
Authors: Chang Hung‐Teh , Ollis David F. 
Published: December 2004

AbstractA generalized power low model, \documentclass{article}\pagestyle{empty}\begin{document}$ \eta \, = \,\eta _0 [1\, + \,(\dot \gamma /\gamma _0 )]^{N - 1} $\end{document}, is shown to described satisfactorily the shear viscosity data for xanthan gum solutions from 0.18 g/L to nearly 4 g/L and low to intermediate shear rates. Since mixing, mass and heat transfer, residence time distributions, and power input for agitation and aeration all depend on shear viscosity, this equation provides a simple prediction of this important quantity over the shear rate ranges characteristic of fermentations.
The kinetic of lactose hydrolysis for the β‐galactosidase from Aspergillus niger
Authors: Flaschel E. , Raetz E. , Renken A. 
Published: December 2004

AbstractThe kinetics of glucose liberation from lactose by means of the β‐glactosidase from Aspergillus niger has been studied in a wide range of the main variables. The analysis shows that the kinetic models proposed so far are not adequate. The main finding is that the reaction rate is not linearly correlated to the enzyme concentration—it increase more than proportionally. This nonlinear relationship results because this lactase can distinguish between α‐and β‐galactose α‐Galactose acts as competitive and anticompetitive inhibitor while β‐galactose is a competitive one. The competitive inhibition of the α‐anomer is approximately 12 times more sever than that of the β‐anomer. The kinetics, including a simplified model for the mutarotation of galactose is given for a temperature of 50°C at a pH of 3.5—the most likely conditions for the application of this lactase in acid whey treatment.
Growth of Trichosporon cutaneum under oxygen limitation: Kinetics of oxygen uptake
Authors: Käppeli O. , Fiechter A. 
Published: December 2004

AbstractThe relationship between oxygen concentration and growth rate in the yeast Trichosporon cutaneum was studied. In order to establish the conditions for purely oxygen‐limited growth, the cells were first grown in a carbon‐limited chemostat, and kinetic parameters determined. The cells were then grown in an oxygen‐limited chemostat at different dilution rates yielding different oxygen uptake rates. The steady‐state dissolved oxygen tension was found at each dilution rate and the corresponding equilibrium dissolved oxygen tension was found at each dilution rate and the corresponding equilibrium dissolved oxygen concentration determined in the effluent medium. The relationship between oxygen concentration and growth rate followed Monod‐type kinetics with an apparent KO of 4.38 × 10−6M.
Preliminary study of a suspended growth predenitrification system
Authors: Shieh Wen K. , Chen Chiu Y. , Chang Sheng D. 
Published: December 2004

AbstractA laboratory study has been conducted to obtained preliminary process information of a suspended growth Predenitrification (SGPDN)system. System performance was evaluated, in terms of chemical oxygen demand (COD) removal, NH3–N removal, system biomass yield and inventory, and effluent qualities, at different solids retention times (SRTs) and recycle ratios. Chemical oxygen demand removal in an SGPDN system occurs mainly in the anoxic reactor, which accounts for 94% of total COD removal. The overall COD removal rate is independent of recycle ratio (ranging from 2–5) used in this study; however, effluent COD increase with increasing recycle ratio. The observed anoxic and aerobic COD removal rates decrease with increasing SRT. The NH3–N removal in an SGPDN system is induced by two mechanisms: assimilatory NH3–N requirement for biomass production in the anoxic reactor and nitrification in the aerobic reactor. The observed anoxic NH3–N removal rate relates directly to the anoxic COD removal rate and agrees fairly well with the assimilatory NH3–N requirement theoretically predicted. The overall NH3–N removal rate is independent of SRTs and recycle ratios used in this study. Biomass yield in an SGPDN system occurs mainly in the anoxic reactor. However, uniform distribution of biomass throughout the entire system is obtained because of the high recycle rate used. The observed biomass yield (YO) decreases with increasing STR. Tertiary treatment efficiency can be achieved in an SGPDN system. More than 90% reduction in feed COD., feed NH3–N, and NO2 + NO3–N is obtained at all SRTs and recycle ratios used in this study. Higher MLVSS loading rates can be applied to a final clarifier without impairing its separation efficiency because of the excellent settleability of the Predenitrification activated sludge.
Preparation and characterization of soluble conjugates of defined molecular sizes prepared by linkage of pepsin and carboxypeptidase A to dextrans
Authors: Chaplin B. , Green M. L. 
Published: December 2004

AbstractSoluble conjugates of pepsin and carboxypeptidase A were prepared by covalent linkage of the enzymes to an amino derivative of dextran. By fractionating the dextran derivatives before and after enzyme coupling, three conjugates, with median Stokes radii between 4.0 and 11.7 nm and with a range of 25% of the median, were prepared from each enzyme. The pepsin and carboxypeptidase A conjugates contained about 35% and 3% protein, respectively. Both types had specific activities close to those of the native enzymes and were stable at −20°C. The pH‐activity curve was unaffected by linkage of either enzyme to dextran. The stabilities at 30°C of pepsin at pH 6–7 and carboxypeptidase A at pH 3.5–9.0 were increased by linkage to dextran. No significant amount of unbound enzyme was released from either type of conjugate in skim milk. The molecular sizes, deduced from the intrinsic viscosities and the diffusion coefficients of all conjugates, were close enough to the Stokes radii to indicate that the molecules were approximately spherical. Physical measurements also indicated that the molecules were dextranlike and highly hydrated.
Optimal quality control of bakers' yeast fed‐batch culture using population dynamics
Authors: Dairaku Kazuo , Izumoto Eiji , Morikawa Hisashi , Shioya Suteaki , Takamatsu Takeichiro 
Published: December 2004

AbstractAn optimal quality control policy for the overall specific growth rate of bakers' yeast, which maximizes the fermentative activity in the making of bread, was obtained by direct searching based on the mathematical model proposed previously. The mathematical model had described the age distribution of bakers' yeast which had an essential relationship to the ability of fermentation in the making of bread. The mathematical model is a simple aging model with two periods: Nonbudding and budding. Based on the result obtained by direct searching, the quality control of bakers' yeast fed‐batch culture was performed and confirmed to be experimentally valid.
Immobilization of Escherichia coli cells with penicillin‐amidohydrolase activity on solid polymeric carriers
Authors: ŽU̇rková E. , Drobník J. , Kálal J. , Švec F. , Tyráčková V. , Vojtíšek V. , Zeman R. 
Published: December 2004

AbstractWhole cells of Escherichia coli containing the enzyme penicillinamidohydrolase EC 3.5.1.11 were immobilized on the surface of modified macroporous copolymers of glycidylmethacrylate with ethylenedimethacrylate and of copolymers of methacrylaldehyde (MA) with divinylbenzene (DVB) by means of glutaraldehyde. These polymeric carriers were modified before cell binding by using ammonia or polyamines, especially ethylenediamine and hexamethylenediamine (HMDA). The highest specific activity and the largest yield in cell immobilization were achieved with the macroporous copolymer of MA and DVB modified with HMDA. The material thus obtained was used in repeated conversions of benzylpenicillin to 6‐aminopenicillanic acid in a stirred batch reactor.
Kinetics of growth and accumulation of aflatoxin B1 by Aspergillus parasiticus in the presence of butylated hydroxyanisole, isoprothiolane, and nystatin
Authors: Yousef Ahmed E. , Marth Elmer H. 
Published: December 2004

AbstractGrowth of Aspergillus parasiticus and accumulation of aflatoxin B1 in the medium that contained antifungal agents were monitored during the growth cycle of the mold. The antifungal agents tested are the food additive (antioxidant), butylated hydroxyanisole (BHA), the pesticide, isoprothiolane, and the antibiotic, nystatin. Growth of the mold was quantified using a newly developed criterion, named the growth coefficient (GC). The GC values were calculated from the growth parameters of the logistic function that fits the growth curve of the mold. At the range of concentrations of additives studied, maxima of growth inhibition were 31.3, 23.1, and 43.6% at 60 ppm of BHA, 70 ppm of isoprothiolane, and 45 units of nystatin/mL, respectively. The ability of the mold to accumulate aflatoxin B1 in its medium [as measured by the accumulation rate constant (α)] In the presence of various levels of the antifungal agents was concentration‐dependent. Sixty parts per million of BHA decreased the value of α by 71.7%, 30 units of nystatin/mL was the most effective concentration of that antibiotic and resulted in only 23.5% inhibition, and isoprothiolane at all its levels stimulated elaboration of aflatoxin B1 by the mold.
Analysis of growth rate effects on productivity of recombinant Escherichia coli populations using molecular mechanism models
Authors: Lee Sun Bok , Bailey James E. 
Published: December 2004

AbstractThe influence of growth rate on Escherichia coli plasmid content and expression of a cloned‐gene product has been described by a mathematical model based upon the molecular mechanism of λdv plasmid replication and known relationships between growth rate and transcription and translation activities of the host cell. The model simulates correctly decreases in plasmid content with increasing growth rate as observed experimentally for pBR322, NR1, R1, and Col E1 plasmids. A maximum with respect to growth rate in intracellular product accumulation is indicated by the model, as is a transient overshoot in product concentration following a shift from smaller to larger growth rate. Available data, although very limited, show the same trends. These results, obtained without parameter or kinetic form adjustments or manipulation, clearly illustrate the advantages of kinetic descriptions of recombinant systems based upon the pertinent molecular mechanisms.
Proline excretion by Escherichia coli K12
Authors: Rancourt Derrick E. , Stephenson James T. , Vickell Gregg A. , Wood Janet M. 
Published: December 2004

AbstractProline excretion from proline overproducing strains of E. coli K12 has been studied as a model chemical production system. We have isolated proline overproducing mutants of E. coli and have shown that uncontrolled synthesis is not sufficient to cause excretion of this amino acid. An episomal mutation causing proline over production has been introduced into a series of otherwise isogenic strains that bear well defined, chromosomal lesions affecting the active uptake and catabolism of L‐proline. A syntropism test reveals that L‐proline is excreted by overproducing strains only if transport and/or catabolism are impaired. Dansyl derivatization and chromatographic analysis of culture supernatants shows that proline is the only amino acid excreted. Batch cultures of an excreting strain in an amino acid production medium yield culture supernatants containing 1 g proline/L, whereas no proline is detectable in supernatants derived from cultures of an overproducing strain with normal transport and catabolic activities. These data reveal that genetic lesions eliminating active uptake can be used to specifically enhance metabolite excretion.
Ethanol production with Saccharomyces cerevisiae under aerobic conditions at different potassium concentrations
Authors: Wümpelmann Mogens , Kjaergaard Leif , Joergensen Birgitte B. 
Published: December 2004

AbstractThe specific ethanol productivity with Saccharomyces cerevisiae grown aerobicly in a chemostat was found to be highly dependent on the ratio of intracellular to extracellular potassium concentration through variations in the energy consumption used for maintenance of the concentration gradient of potassium across the cell membrane. The specific ethanol productivity progressively rose from 0 to 20 mmol h−1 g−1 cell dry matter at a growth rate of 0.17 h−1 when the ratio of intracellular to extracellular potassium concentration was increased from 10 to 80. The ethanol production under potassium limited growth conditions was caused neither by a reduction in the specific respiratory activity nor by variations in the potassium content in cell dry matter. Results which strongly that ethanol production under potassium limited growth conditions is brought about by changes in the ratio of pyruvate oxidase to pyruvate decarboxylase activity through changes in the intracellular pyruvate concentration are presented.
Effect of drying on yield and calorific values of extractables from leafy spurge (Euphorbia esula)
Authors: Wiatr Stanley M. 
Published: December 2004

AbstractThe effect of dehydration on yield and calorific values has been investigated for oils, hydrocarbons, and polyphenols extracted from leaves of Euphorbia esula/ (leafy spurge). Methods of dehydration employed were with a warm oven (50°C), a hot oven (105°C), at room temperature (25°C), and with freeze drying. Generally, dehydration resulted in a loss of yield for all extractives. Noteworthy exceptions were oil yields from the warm‐oven‐ or air‐dried biomass which did not differ significantly from fresh tissue. Significant differences in calorific values (range 4643–5192 cal/g) were observed for each category of whole leafy biomass dehydrated as indicated above. Dehydration reduced the calorific value of oils (range 9483–10,095 cal/g) but tended to increase the calorific values of polyphenols (range 4178–6033 cal/g). NMR spectroscopy of the oil fraction suggested that dehydration did not grossly alter the composition of oils, despite differences in yield and calorific values.
A model for the activated sludge process which considers wastewater characteristics, floc behavior, and microbial population
Authors: Benefield Larry , Molz Fred 
Published: December 2004

AbstractA mathematical model has been developed which describes organics removal, oxygen utilization, ammonianitrogen removal, ortho‐phosphate removal, and biomass production in an aggregated microbial suspension containing a uniform floc size and the organics as a soluble biodegradable material. It is applicable to both steady‐state and transient conditions, as well as to systems experiencing only carbon oxidation or to systems experiencing both carbon oxidation and nitrification. The model, consisting of five partial differential equations and four ordinary differential equations, takes into account the flow pattern in the reactor, intraparticle mass transport of oxygen, organics, ammonia‐nitrogen and ortho‐phosphate, and biochemical reactions by the individual cells embedded in the floc.
A modified matrix perfusion–microcarrier bead cell culture system. II. Production of human (β) interferon in a matrix perfusion system
Authors: Strand Janie M. , Quarles John M. , McConnell Stewart 
Published: December 2004

AbstractAddition of microcarrier beads to a matrix perfusion cell culture system allowed growth of anchorage dependent human foreskin fibroblasts which would not grow in the culture units alone. The utility of the system for collection of cellular products was demonstrated by the induction and harvesting of human (β) interferon. Interferon production was highest in perfusion cultures when medium was circulated throughout the induction and when inducer containing 100 μg/mL polyriboinosinic: polyribocytidylic acid was placed directly in contact with cells in the extracapillary space. These conditions provided 4‐to‐10‐fold greater interferon yields per cell, and approximately 12‐fold increases per vessel, than monolayer cultures. Perfusion grown cells produced interferon at a maximal level for 20 h postinduction compared to approximately 2 h for monolayer grown cells, thus giving a higher total yield of interferon. Other procedures increasing the efficiency of the system included priming with 50 U/mL interferon standard, reinduction of cells, use of antibiotic free medium, reduced serum concentrations, and in vitro aging of the cells.
Enzymatic properties of immobilized Alcaligenes faecalis cells with cell‐associated β‐glucosidase activity
Authors: Wheatley Margaret A. , Phillips Colin R. 
Published: December 2004

AbstractEnzymatic properties of Alcaligenes faecalis cells immobilized in polyacrylamide were characterized and compared with those reported for the extracted enzyme, and with those measured for free cells. Many of the properties reflected those of the extracted enzyme rather than those measured in the free whole cells prior to immobilization, suggesting cell disruption during immobilization. These properties included the pH activity profile, a slightly broader pH stability profile, and the activation energy. Electron micrographs showed evidence of cell debris among the polymer matrix. The immobilized cells were not viable, and did not consume glucose. Thermal stability was less after immobilization with a half‐life of 16 h at 45°C, and 3.5 h at 50°C. The immobilized preparation was more stable when stored lyophilized rather than in buffer, losing 23 and 52% activity, respectively, after six months. The enzyme was irreversibly inhibited by both acetate and citrate buffers. If the immobilized enzyme is to be used in conjunction with cellulases from Trichoderma reesei for cellulase saccharification, the optimal conditions would be pH 5.5 and 45°C in a buffer containing no carboxylic acid groups.
The effect of organosolv pretreatment on the enzymatic hydrolysis of poplar
Authors: Holtzapple Mark T. , Humphrey Arthur E. 
Published: December 2004

AbstractThe use of alcohol/water/catalyst mixtures to delignify wood allows the lignin to be recovered in a usable form while leaving the carbohydrate fraction relatively intact. The effects of temperature, reaction time, and the type of solvent and catalyst on the delignification of milled poplar wood were investigated. The lignin, cellulose, and hemicellulose composition of the pretreated material was measured for each treatment condition. In addition, the pretreated samples were subjected to enzymatic hydrolysis using the cellulases produced by the thermophilic bacterium Thermomonospora sp. YX. The extent of enzymatic hydrolysis was characterized using an empirical model, and the results were used to examine the effectiveness of the pretreatment.
Determining the inhibition constants in the HCH‐1 model of cellulose hydrolysis
Authors: Holtzapple Mark T. , Caram Hugo S. , Humphrey Arthur E. 
Published: December 2004

AbstractThe products of cellulose hydrolysis, glucose and cellobiose, caused noncompetitive inhibition patterns to be exhibited when Thermomonospora sp. YX cellulase hydrolyzed dyed cellulose. The glucose binding constant, β1, was 0.00683 ± 0.00031 L/g and the cellobiose binding constant, β2, was 0.095 ± 0.0058 L/g. Thus, cellobiose was about 14 times more inhibitory than glucose.
State of the art in fermentation air filtration
Authors: Conway Robert S. 
Published: December 2004

AbstractThis article presents several characteristics of a state‐of‐the‐art fermentation air filter. The filter medium is composed solely of PTFE and has an absolute pore size rating of 0.2 μm. Quantitative bacteria and bacteriophage retention is shown based on live organism challenge tests. A nondestructive filter test, correlated to the microorganism challenge tests and called the Forward Flow Integrity Test, is described. This test has a sensitivity of one part in 1012 and can be performed in situ.
A mathematical analysis of enzyme stabilization by a series‐type mechanism: Influence of chemical modifiers
Authors: Henley James P. , Sadana Ajit 
Published: December 2004

AbstractA series‐type enzyme deactivation model is utilized to theoretically analyze and to quantify the effect of chemical modifier concentration on the eventual level of enzyme activity stabilization, α2. An increase in the concentration of phosphate ion and NADP increases α2 for the enzymes studied. One example of each enzyme deactivation is given wherein the introduction of chemical modifiers changes the deactivation mechanism from a single‐step to a series‐type mechanism, and from a series‐type to a single‐step mechanism. Simple empirical equations are proposed to quantify the effect of chemical modifier concentration on α2.
Experiments with an ecosystem adaptation model of biological treatment
Authors: Vavilin V. A. , Vasiliev V. B. 
Published: December 2004

AbstractIn the wake of an earlier advanced multicomponent–multispecies biological treatment model, the authors suggest algorithms to substantially decrease the number of free coefficients. Operation of a number of experiments with the multicomponent‐multispecies model has helped to further our understanding of the mechanism of biological treatment.
Covalent immobilization of FAD and glucose oxidase on carbon electrodes
Authors: Sonawat H. M. , Phadke Ratna S. , Govil G. 
Published: December 2004

AbstractThe effectiveness of attaching flavin adenine dinucleotide (FAD) via a C bridge to Teflon‐bonded carbon black (CB), and the subsequent immobilization of glucose oxidase on the FAD‐modified electrodes has been studied by cyclic voltammetry. When FAD alone is bound to the electrode, it undergoes reduction and oxidation at −0.62 and −0.5 V, respectively—values similar to those obtained with free FAD. Compared to the free enzyme, the reduction of FAD as part of the immobilized enzyme is 200 mV more cathodic, while the oxidation potential remains the same in both cases.