bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of parameters in population models for Schizosaccharomyces pombe from chemostat data
Authors: Kothari Indravadan R. , Martin Gregory C. , Reilly Peter J. , Martin Peter J. , Eakman James M. 
Published: December 2004

AbstractThe integro‐differential growth model of Eakman, Fredriekson, and Tsuehiya has been employed to fit cell size distribution data for Schizosaccharomyces pombe grown in a chemostat under severe product inhibition by ethanol. The distributions were obtained with a Coulter aperture and an electronic system patterned after that of Harvey and Marr. Four parameters—mean cell division size, cell division size standard deviation, daughter cell size standard deviation, and a growth rate coefficient—were calculated for models where the cell growth rate was inversely proportional to size, constant, and proportional to size. A fourth model, one where sigmoidal growth behavior was simulated by two linear growth segments, was also investigated. Linear and sigmoidal models fit the distribution data best. While the mean cell division size remained relatively constant at all growth rates, standard deviation of division size distribution increased with increasing holding times. Standard deviation of the daughter size distribution remained small at all dilution rates. Unlike previous findings with other organisms, the average cell size of Schizosaccharomyces pobme increased at low growth rates.
The kinetic and mass transfer behavior of immobilized invertase on ion‐exchange resin beads
Authors: Kobayashi Takeshi , Moo‐Young M. 
Published: December 2004

AbstractImmobilized invertase was prepared by binding native invertase to a polyamine type ion‐exchange resin. Kinetic behavior of the immobilized invertase on these small pellets was investigated in a packed‐bed reactor. For low flow rates, an effect of interparticle diffusion on the Machaelis constant was observed and a correlation was proposed to evaluate the effect. At high flow rates, Michaelis and inhibition constants were determined and compared with those for native invertase. With large pellets, intraparticle diffusion was found to be important and at high substrate concentrations, the effectiveness factor exceeded unity. Good agreement was found between the theoretical analyses and the experimental data.
The influence of environmental conditions on the macromolecular composition of Candida utilis
Authors: Alroy Y. , Tannenbaum S. R. 
Published: December 2004

AbstractGlucose‐limited chemostat cultures of Candida utilis were cultivated at various pH levels (3.0–7.5), temperatures (15–37.5°C), dilution rates (0.06–0.42 hr−1), and with different nitrogen sources (NH and NO). The ratio of total nucleic acid to protein increased with increase in dilution rate at constant temperature and decreased with increase in temperature at constant dilution rate. The pattern of these variations is consistent with the hypothesis that the nucleic acid to protein ratio is a function of the ratio of the actual dilution rate to the critical dilution rate corresponding to each one of the cultivation temperatures. This ratio is called “reduced dilution rate.” A basis is proposed on which various microorganisms may be compared with respect to the ratios of cell protein to nucleic acid, RNA, ribosomal RNA, and polysomes.
Large scale isolation of choline acetyltransferase from ox brains
Authors: Street G. , Dunnill P. , Lilly M. D. , Glover Vivette A. S. 
Published: December 2004

AbstractA process for the large‐scale isolation of choline acetyltransferase from ox brain has been developed, by scaling‐up an existing laboratory method. 20% of the enzyme was obtained from 17 kg of brain tissue with a 50‐fold purification.
New methods for binding enzyme molecules into a water‐insoluble matrix: Properties after insolubilization
Authors: Broun G. , Thomas D. , Gellf G. , Domurado D. , Berjonneau A. M. , Guillon C. 
Published: December 2004

AbstractNew methods of crosslinking enzyme molecules inside a matrix with or without an inactive protein are described. Enzyme activity yields range between 30 and 80% of the activity of the untreated preparations. Even fragile enzyme systems, for instance those using mobile cofactors, can be efficiently immobilized. Increased resistance towards heat denaturation and proteolysis results.
Dynamic analysis of a microbial process: A systems engineering approach
Authors: Young Thomas B. , Bungay Henry R. 
Published: December 2004

AbstractA general mathematical model of the chemostat system is developed in order to define an experimental program of dynamic testing. A glucose‐limited culture ofSaccharomyces cerevisiae was grown in a chemostat using chemically defined medium. The chemostat was perturbed from an initial steady state by changes in input glucose concentration, dilution rate, pH, and temperature. Dynamic responses of cell mass, glucose, cell number, RNA, and protein concentrations were measured. A number of simulation techniques were used in developing a dynamic mathematical model and in comparing the developed model with experimental data as well as the Monod model. The resulting model was found to be quantitatively accurate and superior to the Monod model. The developed model was interpreted in the light of cell physiology. Adjustment of intracellular RNA fraction was found to be rate limiting in acceleration of cell specific growth rate.
The “azotopure” process for treating nitrogen‐deficient aqueous wastes
Authors: Finn Robert K. , Tannahill Alex L. 
Published: December 2004

AbstractMany chemical and food processing wastes are deficient in nitrogen, and must therefore be supplemented with domestic sewage or ammonia to dispose of them by conventional biological treatment. A more economical treatment, especially of strong wastes, is possible by maintaining a semipure culture of nitrogen‐fixing bacteria in a stirred aerated tank. When operated as a chemostat with 4 to 6 hr detention time, removal of 85% of the COD is possible in a single step without the need for clarifiers or digesters. A clarified effluent could also be produced by flotation or sedimentation of the flocculated bacteria. In that case there would be 99% removal of COD and a reduction in the amount of sludge by two‐thirds over the conventional activated sludge process.
ATP regeneration using immobilized carbamyl phosphokinase
Authors: Marshall David L. 
Published: December 2004

AbstractA simple and efficient system for continuous ATP regeneration is described. The procedure is based on the enzyme‐catalyzed reaction between carbamyl phosphate and ADP. The carbamyl phosphate was generated in situ by reaction between potassium cyanate and potassium phosphate. The enzyme, carbamyl phosphokinase, was isolated from extracts of Streptococcus faccalis and partially purified. Immobilization of the enzyme was achieved using glutaraldehyde‐treated alkylamine glass giving 200–250 units of activity per gram of glass. A column of carbamyl phosphokinase on glass was used to form ATP continuously from ADP, phosphate, and cyanate and lost approximately 16% of the initial activity after 14 days operation at room temperature.
Studies on immobilized papain
Authors: Weetall H. H. , Mason R. D. 
Published: December 2004

AbstractPapain was covalently coupled to ZrO2−coated porous glass by several different methods. These derivatives were characterized and their operational half‐lives determined using casein substrate. Papain covalently coupled to the porous glass, previously converted to a carboxylic acid derivative, through amide linkage gave a 35 day operational half‐life.
Preparation and properties of an immobilized Barley β‐amylase
Authors: Vretblad Per , Axen Rolf 
Published: December 2004

AbstractBarely β‐amylase (α‐1,4‐glucan maltohydrolase, EC 3.2.1.2) has been immobilized by covalent fixation to amino derivatives of epichlorohydrin crosslinked Sepharose mediated by cyclohexyl isocyanide and acetaldehyde. The enzyme conjugates contain up to 35% of the total activity of the β‐amylase added to the coupling mixture. The profiles of activity versus pH and ionic strength are essentially the same for free and immobilized β‐amylase, whereas the resistance to inactivation during storage and use is considerably enhanced by immobilization. Columns with immobilized β‐amylase have been used for continuous degradation of starch. At 45°C, half of the initial activity remains after seven weeks, and the corresponding figure at 23°C is 85 percent.
Mixed culture biooxidation of phenol. II. Steady state experiments in continuous culture
Authors: Pawlowsky U. , Howell J. A. 
Published: December 2004

AbstractExperiments are reported in which a mixed population of organisms was continuous cultured on phenol in a 1‐ to 2‐liter well‐mixed vessel. Steady state phenol concentrations were measured for a range of inlet concentrations from 100 to 800 mg/liter at various dilution rates. These results were compared with those predicted from a model which incorporates the effect of wall growth. It was found that the effect of growth on the walls of the vessel was considerable and increased by a factor of up to 3 × the dilution rate at which 90% conversion of phenol could be obtained.
Insolubilized amylases
Authors: Walton Henry M. , Eastman James E. 
Published: December 2004

AbstractCarrier‐bound immobilized α‐amylases and glucoamylase have been obtained by photopolymerizing aqueous solutions containing acrylamide, a crosslinking monomer, an enzyme‐reactive monomer, an oxygen scavenger, and amylase, and allowing the amylase to react with the entrapping enzyme‐reactive gel matrix evolved. Partial starch hydrolyzates (28 DE corn starch syrup) have been continuously converted to 90–94% dextrose syrups in columns packed with immobilized amylases. The enzymatic heat stability of immobilized glucoamylase gels is discussed.
Citrate production from hydrocarbons by use of a nonsterile, semicontinuous cell recycle system
Authors: Gledhill W. E. , Hill I. D. , Hodson P. H. 
Published: December 2004

AbstractIn order to minimize product toxicity, decrease fermentation cost, prolong the effective production phase, and shorten the lag phase before production in the citrate‐hydrocarbon fermentation by Candida lipolytica ATCC 8661, the use of a nonsterile semicontinuous cell recycle system was investigated. Model experiments demonstrated that portions of the fermentor broth could periodically be removed and centrifuged under nonaseptic conditions with the cells being added to fresh medium and returned to the fermentor. Citrate production continued, however with repeated semicontinuous cell recycle, acid production gradually decreased. It was postulated that this decrease could be attributed largely to physiological trauma and that a truly continuous cell recycle system would minimize these effects and permit maintenance of higher citrate production rates.
Estimation of the disruption in freeze‐pressed Accharomyces cerevisiae by an electronic particle counter
Authors: Magnusson Karl‐Eric , Edebo Lars 
Published: December 2004

AbstractAn electronic particle counter has been used to estimate the disintegration by freeze‐pressing baker's yeast. A counter threshold level which just yielded the maximum count for intact cells was selected. The conductivity of the suspending medium was chosen such that maximum counts were obtained. Under these conditions, the electronic counts agreed well with the visual counts. At a certain threshold level the maximum count was obtained at a lower resistivity (higher conductivity) in the suspending solution with the freeze‐pressed suspension than with untreated cells, indicating that damage to the permeability barrier may occur without disruntion of the cell envelope.Fresh baker's yeast cells do not behave as nonconducting particles. This has to be taken into account when volume determinations with electronic particle counters are performed.
Continuous Cellulase Production
Authors: Mitra Gautam , Wilke Charles R. 
Published: December 2004

AbstractTrichoderma viride QM 9414 growth characteristics on glucose were investigated in single stage continuous stirred tank reactor operation and growth parameters μmax, Ks, QO2 identified. Multistage stirred tank fermentors in series with the first stage utilizing glucose and the subsequent stages utilizing cellulose yielded results in general agreement with theoretical predictions. Significant increase in enzyme productivity over single stage fermentation was obtained in multistage operation.
The design of stirred reactors with hollow fiber catalysts for Michaelis‐Menten kinetics
Authors: Georgakis C. , Chan P. C‐H. , Aris R. 
Published: December 2004

AbstractA method of calculating the conversion in Rony's hollow fiber reactor is outlined. It, is assumed that, the kinetics are of Michaelis‐Menten type and that diffusion within the hollow fiber, as well as through its wall, should be taken into account. The normalization of the Thiele modulus suffices to unify the treatment of internal diffusion and the pseudosteady state hypothesis is found to be valid under almost all conditions.
An evaluation of suspension culture systems for the growth of murine lymphoblastoid lines expressing TL and Thy‐1 alloantigens
Authors: Zwerner Robert K. , Runyan Charles , Cox R. Michael , Lynn Daniel , Acton Ronald T. 
Published: December 2004

AbstractAs a prelude to our studies on TL and Thy‐1 differentiation alloantigens, three murine lymphobhastoid cell lines were examined for expression of these components. Optimal conditions for their mass culture were also determined. Several suspension culture systems were evaluated: (a) 50 ml through 500 ml Wheaton and Bellco spinner flasks as well as 1, 4, and 8 liter Wheaton flasks modified for semicontinuous culture conditions, (b) 3 liter Chemapec Vibrofermentor, and (c) 14 liter New Brunswick fermentor. Utilizing these types of vessels the optimal culture conditions were evaluated as to the effect of: (1) pH, (2) initial concentration of cell inoculum, (3) types of media, and (4) methods of gassing and gas mixtures on the rate of growth and alloantigen expression. This study demonstrated that cells could be cultured on a semicontinuous basis up to densities of 2–4 × 106 cells/ml if a vessel of appropriate dimensions was utilized, the appropriate medium selected, and the pH controlled by CO2 and air overlay. Once these parameters were established the growth of a given cell line was highly reproducible: Under optimal culture conditions the expression of Thy‐1 was maximum while the cells were in the exponential stage of growth and reduced during the lag and stationary phases of growth. The expression of TL did not vary as significantly during the various stages of growth. One cell line grown in medium supplemented with 10% horse serum expressed lass Thy‐1 than those grown in medium containing 10% fetal calf serum. The factors affecting cell growth and alloantigen expression have been considered in the design of a large‐scale suspension culture facility for culturing 1000 liters of cells per week.
Maintenance of perpetual synchrony in HeLa suspension cultures: Question of unbalanced growth
Authors: Thilly W. G. , Arkin D. I. , Nowak T. S. , Wogan G. N. 
Published: December 2004

AbstractUnbalanced growth has been studied in HeLa cell cultures maintained in perpetual division synchrony by periodic inhibition of DNA synthesis. Observation of eight independent cellular parameters indicates that once synchrony has been established the degree of unbalanced growth in later cycles is not as great as is observed with the conventional “double‐block” technique. This significant diminution of unbalanced growth appears to be related to the significantly shorter periods of inhibition of DNA synthesis used in the resynchronization process.
Autoclavable low cost serum‐free cell culture media. The growth of L Cells and BHK cells on peptones
Authors: Keay Leonard 
Published: December 2004

AbstractThe growth of L‐929 cells on a series of peptones, and protein hydrolysates was examined, and it was found that when MEM was supplemented with any of a series of peptones, cell growth was about as good as when serum was used as a supplement. Protein hydrolysates did not support cell growth very well and at higher concentrations actually reduced cell growth. L‐929 and L‐60TM cells were grown both as monolayers or stationary suspensions and in agitated systems in MEM supplemented with 0.5—1% bactopeptone. The addition of macromolecular compounds, insulin or oleic acid had no effect on cell growth. BHK cells were also grown on media supplemented with bactopeptone but richer media (MEM‐alpha, F‐12, or RMPI1640) gave higher cell yields. The cells did not form the monolayers observed with fetal calf serum, but a partial suspension system. Addition of a detergent Darvan #2 gave a totally suspension culture in both stationary and agitated systems.The production of Sindbis virus in BHK cells grown in serum‐free media was examined and the yield of virus was found to be about the same as that produced in serum‐supplemented systems. It is estimated that the cost of cell production media could be reduced by about 90% by the replacement of serum supplement by peptones.
Microbial systems for study of the biotransformations of drugs
Authors: Smith Robert V. , Rosazza John P. 
Published: December 2004

AbstractThe metabolic fate of drugs and other xenobiotics in mammalian organisms represents an area of intense contemporary interest. Traditionally, it is a difficult area of research becausethe biological systems which are used to study biotransformations are capable of yielding only minute quantities of metabolites. Recent developments in comparative biochemistry have made itpossible to link diverse metabolic systems through similarities in the pathways by which they alter foreign organic compounds. The potential thus exists for utilizing microbial metabolic systems to study and possibly predict the metabolic fate of a drug or other foreign compound in mammals. The ease with which microbial systems may be used to obtain large amounts of metabolites is an obvious Advantage.We havhe attemped to review the ways in which mammalian and microbialorganisms metabolize a variety of organic compounds. Attention has been focused on the similarities and differences in the mechanisms by which these living systems metabolize xenobiotics. Particular emphasis has been given to four types of reactions which are important in drug biotransformations: aromatic hydroxylationl; N‐ and O‐dealkylations; and sulfur oxygenations.
A hydrodynamic mechanism for the disintegration of Saccharomyces cerevisiae in an industrial homogenizer
Authors: Doulah M. S. , Hammond T. H. , Brookman J. S. G. 
Published: December 2004

AbstractAmongst the commercial type of homogenizers the Manton‐GaulinAPV homogenizer (APV Company Ltd., Crawley, Surrey, England) which is generally being used for other purposes than cell disintegration processes, has recently been proved to be effective for the breakage of yeast cells. To understand fully the disintegration process occurring in such machines it becomes necessary to describe their functions through mathematical expressionsbased on a realistic hydrodynamic model.A mathematical expression describing the protein release at an applied pressure has been derived from an energy balance in the homogenizer combined with the size distribution function of yeast cell population. This expression has been confirmed experimentally under conditions where it shows that turbulence is the controlling factor in the system. Furthermore it indicates the area where more investigations are needed to improve the efficiency of the process of disintegration.
Kinetics of solka floc cellulose hydrolysis by trichoderma viride cellulase
Authors: Howell J. A. , Stuck J. D. 
Published: December 2004

AbstractA product inhibition model is developed to describe the hydrolysis of cellulose by the Trichoderma viride enzyme system. It is assumed that noncompetitive inhibition by cellobiose dominates the reaction kinetics. Experiments show that this is indeed a reasonable assumption for initial cellulose concentrations of up to 15 g/liter and at hydrolysis extents up to 65′. Kinetic parameters were determined for the noncompetitive inhibitionmodel in batch experiments with durations of up to 1.5 hr. These parameterswere then used in predicting reaction progress for up to 10 hr. Cellobiose was added to the reaction mixture at the onset of some runs and againreliable predictions were obtained for up to 8 hr of hydrolysis. Finally reaction was carried out in a membrane reactor whereby the product cellobiose was being continuously removed and again reasonable predictability was obtained with a higher net reaction rate.
Electrostatic and hydrophobic effects in affinity chromatography
Authors: Morrow R. M. , Carbonell R. G. , McCoy B. J. 
Published: December 2004

AbstractA semi–quantitative theory is developed to explain the nonspecific binding of proteins to substituted affinity chromatography supports due to electrostatic and hydrophobic interactions. The equilibrium constant for the absorption of an enzyme to a solid support, and the rate of desorption of the enzyme are studied as functions of ionic strength. Experimental measurements were taken of the adsorption equilibrium constant and rate of desorption of E. coli β–galactosidase on Sepharose 4B substituted with 3, 3,‐diaminodipropylamine in batch systems. It was found that the enzyme adsorption exhibits a hysteresis effect as the ionic strength is increased and then decreased. Furthermore, the adsorption of theenzyme becomes more reversible at the lower ionic strengths, while at the higher ionic strengths it is essentially irreversible. Using the measured equilibrium constants, and knowing the region of ionic strength where the adsorption becomes reversible, we were able to predict the desorption of enzyme in a continuous stirred tank as a function of time when a decreasing linear gradient of ionic strength was introduced into a slurry. It was found that the presence of another protein, hemoglobin, does not affect these results, and therefore can be separated from the enzyme.
Kinetics of biosynthesis of polyene macrolide antibiotics in batch cultures: Cell maturation time
Authors: Martin Juan F. , McDaniel Lloyd E. 
Published: December 2004

AbstractThe changes in several parameters of the candicidin fermentation (total, mycelium‐associated, and extracellular product formation; growth rate; DNA content; glucose utilization; dissolved oxygen in the broth; and oxygen uptake rate) during the trophophase‐idiophase transition are compared with previously reported data for the polyene macrolides, candidin and candihexin. The maturation time, tm, and the productformation rate constant, kp, have been calculated for each of the three polyene macrolides using a simple mathematical model. Slow‐feeding of glucose, which resulted in candidin and candihexin overproduction has been shown to increase the polyene formation rate constant and toretard trophophase to idiophase transition (longer maturation time). The opposite effect is achieved by repeated feeding of soybean meal. The values of the maturation times and polyene formation rates obtained were used to predict the production of polyene macrolide antibiotics in batch cultures.