bluuebunny/crossref_metadata_2025 huggingface dataset:
Distributed parameter model of an airlift fermentor
Authors: Merchuk Jose C. , Stein Y. , Mateles R. I.
Published: December 2004

A distributed parameter model for an airlift fermentor is presented. A riser represents the airlift fermentor, with plug flow in both gas and liquid phases, a well‐mixed section that acts as gas separator, and a downcomer with plug flow. The set of equations proposed makes possible both the understanding and design of the system. Macroscopic balances shows a behavior that is very close to conventional continuous stirred tank fermentor from the viewpoint of biomass production. In addition, the model predicts concentration profiles of biomass, substrate and oxygen in the liquid, and oxygen in the gas phase. This allows estimation of optimal gas flow rate for sufficient oxygen transfer with minimum energy input.
Partial acid hydrolysis of cellulosic materials as a pretreatment for enzymatic hydrolysis
Authors: Knappert Diane , Grethlein Hans , Converse Alvin
Published: December 2004

Partial acid hydrolysis was studied as a per treatment to enhance enzymatic hydrolysis, such a pretreatment was carried out in a continuous flow reactor on oak corn Stover, newsprint, and Solka Floc at temperatures ranging from 160 to 220°C, acid concentration ranging from 0 to 1.2%, and a fixed treatment time of 0.22 min. The resulting slurries and solids were than hydrolyzed with Trichoderma ressei QM 9414 cellulase at 50°C for 48 hr. For all substrates except Solka Floc, increased glucose yields were achieved during enzymatic hydrolysis of the pretreated materials as compared to hydrolysis of the original substrate. In several cases, after pretreatment, 100° of the potential glucose content of the substrate was converted to glucose after 24hr of enzymatic hydrolysis. It is felt that the increased glucose yields achieved after this pretreatment are due to acid's removal of hemicellulose, reduced degree of polymerization, and possibly due to a change in the crystal structure of the cellulose.
Analysis of fermentation processes using flow microfluorometry: Amylase and protease activities in Bacillis subtilis batch cultures
Authors: Fazel‐Madjlessi Jila , Bailey James E.
Published: December 2004

Flow microfluorometry, which provides detailed information on the state of a microbial population, has been employed to characterize the Bacillus subtilis population during time intervals in which significant changes in the culture amylase activity occur. Four different batch experiments have been conducted, and the influences of inoculum age, fermentation temperature, and aeration rate on microbial population dynamics and amylase activity have been examined. Relatively high rates of amylase activity increase are observed twice during the batch, first as double cells initiate sporulation and later during germination. Rapid decreases in amylase activity are observed in highly (25–50%) sporulated populations, and in at least one experiment, during a transition from large, rounded protoplast forms to normal rod morphology. Amylase and protease activities do not follow parallel nor proportional trajectories in these 72 hr batch fermentations.
Efficiency of bovine liver catalase as a catalyst to cleave H2O2 added continually to buffer solutions
Authors: Ibrahim M. , Schlegel H. G.
Published: December 2004

Empirical estimations of H2O2 concentration in a system containing bovine liver catalase and continually supplied with H2O2 were done to evaluate the efficiency of the enzyme to cleave H2O2. It was found that the continuous addition of H2O2 leads to the formation of steady‐state concentrations of H2O2 in the medium. At a constant catalase concentration both the level and the duration of the steady state are dependent on the flow rate of H2O2. The increase of the catalase concentration in the medium does not change the steady‐state level, it merely leads to the maintenance of the steady state for longer durations. At higher flow rates of H2O2, no steady state could be maintained, even when catalase was present in high excess. The incomplete cleavage of H2O2 by catalase under these conditions is due to the low affinity of catalase toward H2O2 (high Km value, apparent Km = 0.1M H2O2) and to the rapid inactivation of the enzyme during the continuous addition of H2O2.
Kinetic study on thermal stability of immobilized invertase
Authors: Ooshima Hiroshi , Sakimoto Masuo , Harano Yoshio
Published: December 2004

The kinetic study of the thermal stability of three kinds of invertases: native, immobilized on porous glass covalently, and on ion‐exchange resin ionically, has been carried out, measuring their enzymatic activity for sucrose hydrolysis. Thermal deactivations of all invertases obeyed first‐order kinetics, being independent of substrate concentration, with kd and ΔEd, ΔSd* as shown in Tables I and II, respectively. Based on these parameter values, the effects of immobilization and pH at deactivation on the stability have been considered, and it was suggested that the ionic bond gives a more loosely deformed enzyme than the covalent bond.
Evaluation of steady‐state‐biofilm kinetics
Authors: Rittmann Bruce E. , McCarty Perry L.
Published: December 2004

Laboratory‐scale biofilm reactors were used to evaluate a model of the kinetics of steady‐state biofilm and the concept that there is a minimum concentration, Smin, below which no steady‐state activity can occur. With acetate as the ratelimiting substrate, the steady‐state concept of Smin was verified for naturally grown biofilms. Substrate removal and biofilm thickness declined rapidly as the substrate concentration approached Smin, which was 0.66 mg/liter for acetate. Using independently derived kinetic parameters, the model of steady‐state‐biofilm kinetics successfully predicted substrate utilization and biofilm thickness without the need for fitting factors. The results imply that organic materials may persist in water and wastewater, in part, because they are too low in concentration to supply sufficient energy to sustain the microorganisms.
Protease production by immobilized mycelia of Streptomyces fradiae
Authors: Kokubu Toshinori , Karube Isao , Suzuki Shuichi
Published: December 2004

Streptomyces fradiaewas immobilized in polyacrylamide gel prepared from 5% total acrylamide (90% acrylamide and 10%N,N′‐methylenebisacrylamide). Production of protease by the immobilized mycelia was attempted in a batch system. A dilute medium containing 0.5% starch, 0.5% meat extract, and 0.05% yeast extract was employed. The reusability of the immobilized and washed mycelia was examined. The activity of protease production by washed mycelia was rapidly decreased with increasing use cycles. The activity of the immobilized mycelia increased gradually, and reached a maximum after ten use cycles. Then, the activity gradually decreased with increasing reaction cycles. This might be caused by destruction of the gels. On the other hand, the sterilization of the surface of the immobilized mycelia was effective for elongation of the lifetime. As a result, the half‐life of protease production by the sterilized immobilized mycelia was about 30 days. The rate of protease production by immobilized mycelia was 12,000 U/ml/hr. This value was four times higher than that by submerged culture.
Acidogenic fermentation of corn stover
Authors: Datta Rathin
Published: December 2004

Corn stover was fermented by anaerobic acidogenic bacteria to produce volatile (C2–C6) organic acids. Mild pretreatment with dilute alkali solutions produced a two‐fold increase in fermentability. A mixture of lime and sodium carbonate was found to be a better pretreatment agent than sodium hydroxide. Methane generation was inhibited by low temperature (⩽ 25°C) and high solids [≥ 2.5% (w/v)] fermentation. Volatile acid yields of 0.5–0.55 g acetic acid equiv/g dry ash‐free (DAF) stover could be obtained in batch fermentations. Several extractants and extraction solvents for organic acids were found to be nontoxic to acidogenic fermentation. The data show that acidogenic fermentation can produce useful volatile fatty acids in high yields from a complex lignocellulosic feedstock. These fermentations are nonsterile, need no stirring, and are easy to run. Moreover, cellulose, pentosans, and other carbohydrates are directly utilized by acidogenic bacteria. Hence, acidogenic fermentation could be useful in converting biomass to chemical feedstocks and fuel.
Development of a hollow‐fiber system for large‐scale culture of mammalian cells
Authors: Ku K. , Kuo M. J. , Delente J. , Wildi B. S. , Feder J.
Published: December 2004

A flat‐bed hollow‐fiber cell culture system has been developed which maximizes the utilization of the large fiber surface while diminishing significantly the problems inherent in a cartridge‐type reactor. The reactor core consists of a shallow bed of hollow fibers sandwiched between two stainless‐steel microporous filter plates through which the media flow is directed normal to the plane of the fiber bed. Reactors with both 930 and 9300 cm2 of fiber surface have been successfully constructed and operated. A variety of cells has been grown in these reactors including SV3T3 cells, baby hamster kidney cells, Vero cells, and rhesus money kidney cells, and cell products such as plasminogen activator and migration inhibition factor (MIF) were produced. This system offers an excellent prototype for scaleup design.
An outdoor biophotolytic system using the cyanobacterium Anabaena cylindrica B629
Authors: Smith Geoffrey D. , Lambert Grant R.
Published: December 2004

The cyanobacterium Anabaena cylindrica B629 was suspended in small glass beds and incubated in a gas‐tight glass vessel outdoors under a gas atmosphere comprising carbon monoxide (0.2%), acetylene (5%), oxygen (6.5%), and nitrogen. The solution phase initially contained sodium bicarbonate (10mM) at pH 7. Under these conditions the organism continuously produced hydrogen gas for over three weeks. The temperature of the culture was maintained below 30°C and minimum night temperatures were recorded. The vessel was covered by a shadecloth, which reduced the natural illumination by approximately 70%. The system is an alternative to those requiring the strict absence of oxygen and little nitrogen, and requires virtually no attention during the incubation period.
The scale‐up from 0.1 to 100 liter of a unit process system based on 3‐mm‐diameter glass spheres for the production of four strains of FMDV from BHK monolayer cells
Authors: Whiteside J. P. , Spier R. E.
Published: December 2004

This paper describes the scale‐up from 0.1 to 100 liter of the unit process based on 3‐mm‐diameter glass spheres for the growth of BHK monolayer cells. The production of four strains of FMD virus at the 0.1‐, 10‐, and 100‐liter scales was examined. Cell growth was estimated from measurements of the concentration of glucose in the growth medium, while the release of virus was inferred from measuring the concentration of LDH in the culture supernatant fluid. The yields of virus at 0.1‐, 1‐, and 10‐liter scales were similar but that from the 100‐liter version was somewhat lower. The reason for this lower yield and the method used to overcome it over outlined.
Photometabolic production of hydrogen from organic substrates by free and immobilized mixed cultures of Rhodospirillum rubrum and Klebsiella pneumoniae*
Authors: Weetall Howard H. , Sharma Bhavender P. , Detar Clarence C.
Published: December 2004

A culture of R. rubrum cells apparently contaminated with K. pneumoniae were immobilized by entrapment in agar. This system was used as model for hydrogen production by photometabolic means. Observed results indicated that the contaminant exerted a major influence on the observed results. This preparation, when immobilized and used in a specifically designed reactor with glucose substrate, showed operational half‐lives of approximately 1000 hr. The feasibility of using this “mixed” culture for producing hydrogen from acid hydrolyzed cellulose and wood sawdust was also examined.
Energetic yields associated with hydrocarbon fermentations
Authors: Erickson L. E.
Published: December 2004

Energetic yields associated with microbial growth on hydrocarbons are investigated and compared with values for other organic substrates. Both cell growth and extracellular product formation are investigated. Both carbon and energy limitations are considered in estimating theoretical yields. Carbon, available electron, and ATP balances are used in the theoretical analysis. The results indicate that the availability of carbon may limit growth and product formation.
Inorganic carbon sources and biomass regulation in intensive microalgal cultures
Authors: Goldman Joel C. , Dennett Mark R. , Riley Carol B.
Published: December 2004

Three freshwater and one marine algal species were grown under inorganic carbon limitation in laboratory continuous cultures. Comparisons were made between HCO3− alkalinity and bubbled CO2 as carbon sources. HCO3− alkalinity was an excellent source of inorganic carbon below specific pH levels, but chemical precipitation at high pH placed an upper limit on productivity that was far lower than potential light‐limiting levels. With bubbled CO2 it was possible to achieve light limitation. The main factor controlling productivity was the mass flux of inorganic carbon added to the culture, which is the product of gas flow rate and influent P level. Small bubbles were more efficient than large bubbles at low gas flow rates and P levels, but led to froth flotation of algal cells and concomitant reductions in productivity at high bubble rates. At 1% CO2 productivity was still dependent on mass fluxes of added carbon, but was independent of bubble size. At high bubble rates with 1% CO2 narcosis was evident. Maximum yields occurred at intermediate dilution rates when inorganic carbon was supplied via bubbled gas.
Separation of meso and racemic 2,3‐butanediol by aqueous liquid chromatography
Authors: Voloch Marcio , Ladisch Michael R. , Rodwell Victor W. , Tsao George T.
Published: December 2004

Fermentation of xylose by Klebsiella pneumoniae (ATCC 8724) producers meso and nonmeso 2,3‐butaneodiol. The enzyme Kinetic of 2,3‐butanediol stereoisomer formation from acetone is currently under study in our laboratory. Modeling of these kinetics requires resolution of meso and racemic 2,3‐butanediol and positive identification of these resolved components. We report their resolution by aqueous liquid chromatography on both an analytical and a preparative scale. The resolved stereoisomer were identified by a combination of gas chromatography, gas chromatography/mass spectroscopy, 13C‐NMR spectroscopy, optical activity, and, melting points of the m‐dinitrobenzoyl eaters of meso and racemic 2,3‐butanediol. An aqueous liquid chromatographic technique for resolving and qualifying major components of a butanediol fermentation mixture in 40 min is presented.
A distributed parameter model for an airlift fermentor. Effects of pressure
Authors: Merchuk José C. , Stein Yehuda
Published: December 2004

A previously presented model for an airlift fermentor is extended by considering the variations of pressure along the tubes. The fluid dynamics of the system is represented with the acid of correlations obtained from experiments. Only oxygen concentrations are considerations are considered. The influences of the various parameters affecting the system are analyzed. The model allows prediction of oxygen concentrations in the different points of an airlift fermentor and calculation of the best values of the gas flow rate.
A unified partition coefficient theory for chromatography, immobilized enzyme kinetics, and affinity chromatography
Authors: Taylor James B. , Swaisgood Harold E.
Published: December 2004

A unified treatment of systems containing immobilized biochemical and chromatographic systems was developed from basic thermodynamic considerations of partitioning in biphasic systems. Division of the overall partitions coefficient into electrostatic and nonelectrostatic interactions provided an effective stratagem for analysis of these systems. The properties of both strong and weak ionogenic matrices were explored. It was Found that the matrix charge concentration and the bulk solutions pH and ionic strength completely determine the electrostatic partition coefficient. Hence, the relationships developed allow prediction of partition coefficients from readily obtainable experimental parameters. It was also shown that even at low concentrations, the presence of immobilized protein can alter the properties of the matrix phase. However, a weak ionogenic matrix has an unusual property which allows for a biological switching device. Ina characteristics pH range, such matrices will maintain a constant micro environmental pH while the partitioning of a substrate ion is greatly variable. Finally, the theoretical treatment suggests simple procedures for determination of binding constants from affinity or adsorption chromatography.
Combined product and substrate inhibition equation for cellobiase
Authors: Hong Juan , Ladisch Michael R. , Gong Chen‐shung , Wankat Phillip C. , Tsao George T.
Published: December 2004

Cellobiase (CE 3.2.1.21) is a β‐glucosidase which hydrolyzes cellobiose to glucose and is known to be subject to both product and substrate inhibition. This work report a model which combines both product and substrate inhibition effects for cellobiase isolated from a commercial preparation of Trichoderma viride from Miles Laboratories (Elkhart, IN). An integrated rate equation is presented which predicts the trends of time courses for hydrolyses of cellobiose a t concentrations ranging from 14.6–1416mM cellobiose. The constants used in the model (determined from initial rate data) are compared to those reported for cellobiase obtained from other sources of T. Viride. Most notable in this comparison is the apparently higher activity and reduced inhibition of this enzyme compared to other sources of cellobiase.
Continuous culture in combined backmix–plug‐flow–tubular‐loop fermentor configurations
Authors: Toda K. , Dunn I. J.
Published: December 2004

Several 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

Various 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

A 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

The 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

The 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

A 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

Soluble 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

An 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

Whole 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

Growth 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

The 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

Proline 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

The 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

The 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

A 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

Addition 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

Enzymatic 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

The 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

The 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

This 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

A 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

In 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

The 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.
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

The 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

An 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

The 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

Dihydrofolate 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

Aerobic 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

Steam‐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.