bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design and synthesis of nonpeptide peptidomimetic inhibitors of renin
Authors: Smith Amos B. , Akaishi Ryouichi , Jones David R. , Keenam Terence P. , Guzman Mark C. , Holcomb Ryan C. , Sprengeler Paul A. , Wood John L. , Hirschmann Ralph , Holloway M. Katharine 
Published: December 2004

AbstractThe desire to replace the amide backbone of renin inhibitors with a new scaffold led us to explore vinylogous amides (enaminones). An initial attempt proved unsuccessful, a result explained after the fact via docking experiments. Based on this lesson, we designed a different vinylogous amide scaffold which incorportated one or more pyrrolinone rings into the backbone. Three of the four compounds gave IC50s in the 0.6 to 18 μM range. These compounds did not inhibit HIV‐1 protease. Taken together, the results reported herein provide insights into the role of hydrogen bonding and steric interactions for binding to renin. © 1994 John Wiley & Sons, Inc.
Submerged culture of hamster kidney cells in a stainless steel vessel
Authors: Telling R. C. , Elsworth R. 
Published: December 2004

AbstractThis paper describes the design and operation of an industrial type culture system for the submerged growth of BHK 21 cells at a volume of 30 l. Using a modified Eagle's medium and with the culture controlled at pH 7.4 ± 0.05 and at a temperature of 35 ± 0.25°C., the cells grew from 0.5 × 106 to about 2.5 × 106 viable cells/ml. in 50 hr. at stirrer speeds of 330 and 460 rpm. The significance of certain aspects of design and operation of a culture system of this type is discussed.
Optimal control of an enzyme reaction subject to enzyme deactivation. I. Batch process
Authors: Ho Lewis Y. , Humphrey Arthur E. 
Published: December 2004

AbstractThis paper is concerned with the study of an enzymatic system in a repeated batch process where the enzyme is subject to deactivation. The particular system studied was the enzymatic hydrolysis of Penicillin G to 6‐aminopenicillanic acid. Utilizing standard optimization techniques, pH and temperature control policies were determined that would maximize the product yield.
A method for large reduction of the nucleic acid content of yeast
Authors: Canepa A. , Pieber M. , Romero C. , Toha J. C. 
Published: December 2004

AbstractA method for large reduction of nucleic acid content of Saccharomyces cercvisae is described. This method is based on yeast suspension in phosphate solution (50mM), heat shock following the Maul et al. (Nature 228, 181 (1970)) procedure, and dialysis or washing with phosphate solution of alkaline pH. When the extraction process is carried out at pH 12, sodium phosphate can be replaced by sodium chloride with the same results. Under these conditions the protein mg/nucleic acid mg ratio attains values of 50–60, (10 times the initial ratio). At this alkaline pH, washing can be done with distilled water with equally good results.
Kinetic behavior of mixed populations of activated sludge
Authors: Chiu S. Y. , Fan L. T. , Kao I. C. , Erickson L. E. 
Published: December 2004

AbstractThe kinetic behavior of heterogeneous microbial populations of sewage origin was studied in a single‐stage isothermal continuous flow completely mixed aeration tank. A series of experiments were carried out at various dilution rates using glucose as the growth limiting substrate. The steady‐state behavior of the system was observed at each dilution rate and the results were found to fit fairly well with the steady‐state equation bayed on the Monod model with an endogenous respiration term included, i.e., μ = μmS/(Ks + S) − Kd. The growth kinetics of cells harvested at steady state for each dilution rate were studied using batch experiments. The multiple response data of the system as functions of time were used to estimate the parameter values in the above kinetic model. It was found that values of the growth parameters changed significantly and systematically with cell population. For example, values of μm were high at high dilution rates and low at low dilution rates. It was also found that only those batch growth parameters from cells obtained at fairly high dilution rates are comparable with those estimated by the results of steady‐state operations. The results of this investigation suggest that (1) different cell populations pre dominated at different steady‐state dilution rates, with high dilution rates resulting in predominantly fast‐growing organisms and low dilution rates resulting in predominantly slow‐growing cells, and (2) risk exists in any randomly picked batch experiment to predict the steady‐state behavior of the system when heterogeneous microbial populations must be used.
Biotechnology report: Solid state fermentations
Authors: Hesseltine C. W. 
Published: December 2004

AbstractA unique method is described by which large yields of secondary metabolites arc produced on solid substrates. The process involves the use of moist substrates which are continuously agitated in appropriate fermentation equipment. The amount of agitation, aeration, and moisture can be varied. Extremely high yields of secondary metabolites such as ochratoxin and aflatoxin were obtained using Aspergillus and Penicillium species. The process prevents sporulation of the fungus and because of the nature of the solid substrate makes recovery of the product easier than in conventional liquid media. The substrates include rice, corn, wheat, and other cereals.
Release of protein from Bakers' yeast (Saccharomyces cerevisiae) by disruption in an industrial agitator mill
Authors: Currie J. A. , Dunnill P. , Lilly M. D. 
Published: December 2004

AbstractRelease of protein from a suspension of bakers' yeast (Saccharomyces cerevisiae) by disruption in an industrial agitator mill has been studied. Protein release on disruption in the mill is a first‐order rate process. The rate constant is dependent on at least six parameters. Increased disruption efficiency was obtained at higher agitator speeds, greater loading of bead attritive elements and lower rates of upward recycle of yeast suspension through the mill. An increase in temperature from 5 to 42°C was accompanied by a reduction in disruption efficiency of approximately 20%. With optimal values of the parameters examined the throughput of the mill is 5.32 kg/hr of soluble protein for 90% disruption.
The effect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concentrate
Authors: Torma A. E. , Walden C. C. , Duncan D. W. , Branion R. M. R. 
Published: December 2004

AbstractThe effects of carbon dioxide‐enriched air on the rate of zinc extraction during the microbiological leaching of a, high‐grade zinc sulfide concentrate by Thiobacillns ferrooxidans have been studied. Under normal air‐aeration conditions, the leach rate is limited initially by the availability of solid substrate surface area per unit volume of leach liquor, then by availability of carbon dioxide. If carbon dioxide‐enriched air is supplied, along with excess substrate, the zinc extraction rate increases as the carbon dioxide content increases until some other, as yet unknown, factor becomes limiting.
Model for the growth of aerobic microorganisms under oxygen limiting conditions
Authors: Ryder D. N. , Sinclair C. G. 
Published: December 2004

AbstractA simple dynamic model is proposed which will allow fermenters to be run at throughputs which fully utilize the mass transfer capabilities of the fermenters while not decreasing the yield from the substrate. The model is compared with one previously proposed, which was originally formulated for double substrate limitation when both substrates were supplied in the feed. Computer solutions of the model are given which show the effects of the parameters used. Experimental results from growing Candida utilis on a high concentration of glucose were found to be similar to those predicted by the model.
Continuous production of L‐aspartic acid by immobilized aspartase
Authors: Tosa Tetsuya , Sato Tadashi , Mori Takao , Matuo Yuhsi , Chibata Ichiro 
Published: December 2004

AbstractVarious methods were tried for the immobilization of aspartase, and the preparation having the highest activity was obtained when partially purified aspartase from Escherichia coli was entrapped into polyacrylamide gel Iattice. Enzymatic properties of the immobilized aspartase were investigated and compared with those of the native aspartase. With regard to optimum pH, temperature, concentration of Mn++, kinetic constants and heat stability, no marked difference was observed between the native and immobilized aspartases.By employing an enzyme column packed with the immobilized aspartase, conditions for continuous production of L‐aspartic acid from ammonium fumarate were investigated. When a solution of 1M ammonium fumarate (pH 8.5, containing 1mM MnCl2) was passed through the aspartase column at the flow rate of SV = 0.08 at 37°C, the highest rate of reaction was attained. From the column effluents, L‐aspartic acid was obtained in a good yield.
Some methods for processing of single‐cell protein
Authors: Hedenskog Gudmund , Mogren Hårkan 
Published: December 2004

AbstractMethods for the production of protein concentrates, with a low content of nucleic acid, in kilogram quantities from yeast have been studied with the aid of equipment designed for operation on pilot‐plant scale. The influence of drum drying and mechanical disintegration on the nutritive value of the yeast was also investigated. Drum drying and mechanical disintegration improved the nutritive value of the yeast but high extractability of protein and nucleic acid was only obtained after mechanical disintegration.Protein concentrates without and with cell walls were produced from mechanically disintegrated yeast. The different fractions which were obtained when separating cell walls and precipitating protein by heating at alkaline pH, were analyzed. After protein precipitation, about 90% of the RNA could be precipitated from the supernatant by addition of acid, giving a product containing 50% RNA of the dry weight. The protein precipitate obtained after cell wall separation had an RNA content of less than 2% and contained 70–l75% of the amino acids in the starting yeast material. Protein concentrates containing cell walls were produced by precipitating protein by heating at alkaline pH directly after mechanical disintegration. The content of RNA was about 2% and the yield of amino acids was 70–80%. It was found that the nutritive value of the protein concentrate was higher than that of the starting yeast material. To produce such a protein concentrate on a large scale, the process described can probably be employed.
Immobilized glucoamylase on porous glass
Authors: Marsh David R. , Lee Yoon Y. , Tsao George T. 
Published: December 2004

AbstractA study was made to determine the controlling mass transfer resistance in the overall reaction rate for conversion of maltose to glucose, catalyzed by glucoamylase immobilized onto porous glass. For normal operation of a packed column and air‐stirred batch reactor, the rate controlling step was found to be the internal resistance of simultaneous pore diffusion and chemical reaction. Experimental effectiveness factors were determined and are compared with those derived from a theoretical diffusion model based on Michaelis‐Menten kinetics. Also given are temperature and pH relationships for the free and immobilized glucoamylase.
Penicillin amidase production by bacillus megaterium
Authors: Acevedo F. , Cooney C. L. 
Published: December 2004

AbstractPenicillin amidase, an enzyme which hydrolyzes benzylpenicillin to 6‐aminopenicillanic acid and phenylacetic acid, is produced by Bacillus megaterium ATCC 14945 as an extracellular enzyme. We used this system as a model to examine the effects of nitrogen, sulfur, and phosphorous limitation on enzyme production in continuous culture. For these studies, we developed a minimal medium for B. megaterium which contained histidine as the sole nitrogen source. Batch experiments showed that this enzyme is produced as a growth‐associated metabolite. Enzyme production was shown to be a function of the growth‐limiting conditions and the concentration of the inducer, phenylacetic acid. Sulfur limitation in continuous culture yielded enzyme activities approximately three to five times those observed in nitrogen‐ and phosphorous‐limited chemostats. These results are discussed in terms of the environment's influence on enzyme production in continuous culture.
Hydrocarbon fermentations: Oxidation mechanism and nonionic‐surfactant effects in a culture of Candida lipolytica
Authors: Whitworth D. A. , Moo‐Young M. , Viswanatha T. 
Published: December 2004

AbstractOxidation rates of several alkane substrates by C. lipolytica ATCC 8661 grown on n‐dodecane were determined using a Warburg Respirometer. Substrates were emulsified using Span 20, Span 80, Tween 20, Tween 80, and Triton X‐100 surfactants and the effects of these surfactants on oxidation and growth were determined. The oxidation rates of a number of intermediates, including lauric acid and lauryl alcohol, were also assessed. Responses of dodecane‐grown C. lipolytica to select substrates were compared to the corresponding behavior with glucose‐grown yeast and with baker's yeast. The role of surfactants in hydrocarbon fermentations is discussed in the light of the present and previously published data.
Cofactor recycling in an enzyme reactor. A comparison Using free and immobilized dehydrogenases with free and immobilized NAD
Authors: Wykes J. R. , Dunnill P. , Lilly M. D. 
Published: December 2004

AbstractThe requirements for enzymic cofactor recycling have been investigated in a system employing alcohol and lactate dehydrogenases. The interactions of various combinations of free dehydrogenases or dehydrogenases immobilized either to the same or separate supports, with free NAD, a soluble highmolecular weight derivative of NAD or an insoluble derivative of NAD have been examined.
Enzymes immobilized on alumina and stainless steel supports
Authors: Charles M. , Coughlin R. W. , Paruchuri E. K. , Allen B. R. , Hasselberger F. X. 
Published: December 2004

AbstractEnzymes can be sorbed on inorganic carriers followed by crosslinking with glutaraldehyde. In some cases superior results are obtained when the support is precoated with a porous layer of titanium oxide. Immobilized lactase prepared in this way retains essentially all its activity when stored under water at 23°C for long periods of time and loses activity only slowly while treating cheese whey at 55°C over the course of several weeks contact time. Furthermore, catalyst activity is unaffected by frequent sanitization. Optimum pH for these immobilized‐lactase catalysts (enzyme produced from A. niger) is about 3.0 and optimum temperature is about 60°C. Amyloglucosidase catalase, L‐asparaginase, and trypsin have also been immobilized by these techniques.
Enzyme immobilization on macroreticular polystyrene
Authors: Baum George 
Published: December 2004

AbstractMacroreticular polystyrene beads may be converted into suitable supports for covalent binding of enzymes. In many respects the supports are physically similar to controlled pore glass (CPG). Our results for immobilized glucoamylase were very similar to published results using CPG as a carrier. The characteristics of immobilized papain were less satisfactory. The product exhibited a Z‐shaped activity‐time profile suggestive of the involvement of multiple mechanisms.
Production of a plasmin inhibitory substance by Scopolia japonica suspension cultures
Authors: Misawa Masanaru , Tanaka Hozumi , Chiyo Osamu , Mukai Noboru 
Published: December 2004

AbstractA potent inhibitory agent against human plasmin, fibrinolytic proteinase, has been found in the extracts of callus tissue of Scopolia japonica. Effects of cultural conditions on cell growth and production of the plasmin inhibitory substance by this cell line in suspension cultures were examined in MurashigeSkoog's medium. More than l.5 mg of the inhibitor, as t‐amino cyclohexane carboxylic acid, a synthetic plasmin inhibitor, were observed to accumulate per ml of medium containing 0.83 g of NH4NO3 and 7.6 g of KNO3 per liter as well as suitable levels of growth hormones.Addiction of antibiotics and deformers were examined in preliminary tests for large scale cultivation. Semicontinuous culture on a small scale in a glass cylinder, was also tested and growth rate of 1.29 g/liter/day (by dry wt) was obtained. Plasmin inhibitory activities in the extracts of the results intact plant and in cultured cells of S. japonica were compared and the results indicated that cell suspension culture was superior to extraction the natural plant for inhibitor production.
Effects of internal diffusion on the lineweaver‐Burk plots for immobilized enzymes
Authors: Gondo Shinichiro , Isayama Shogo , Kusunoki Koichiro 
Published: December 2004

AbstractThe effect of internal diffusion on the slope and the intercept of the LineweaverBurk plots for the immobilized enzyme was considered theoretically and it was found that the slope and the intercept are influenced not only by the dimensionless term M but also by the range of the dimensionless bulk substrate concentration ζb. The dependencies of the slope and the intercept on M and on the rate of ζb are shown graphically. Accurate estimations of M and the maximum velocity of the immobilized enzyme give the true, not apparent, Michaelis constant. It is shown that the linear correlations in the Lineweaver‐Burk plots do not always coincide with the correlations for the estimation of M and the maximum velocity. It also is shown that large values of M may induce a serious error in the estimation of M with large values of ζb and in an estimation of the maximum velocity with small values of ζb.
Transient kinetics of yeast growth in batch and continous culture with an inhibitory carbon and energy source
Authors: Ko R. Y. C. , Edwards V. H. 
Published: December 2004

AbstractGrowth and acetate metabolism by Candida utilis (ATCC 9226) is reported for both acetate‐ and zinc‐limited cultures in defined media. Acetate concentrations were varied from suboptimal to inhibitory levels in both types of media in differential shake flask culture and in batch and continuous cultures in stirred fermentors. Transient responses of steady‐state cultures to small or large additions of concentrated sodium acetate, or to shifts in dilution rate or inlet acetate concentration are compared with one another and with simple mathematical models of growth and acetate metabolism. Exponential growth was observed during unrestricted growth (differential shake flask and batch cultures) with both types of media. Addition of acetate during unrestricted growth always caused lags and for larger pulses, lower specific growth rates were observed after exponential growth resumed. Inhibition by high acetate concentrations was much greater in acetate–limited than in zinc–limited cultures. During restricted growth (steady‐state, continuous cultures), high acetate concentrations again consistently caused growth lags but stimulated, inhibited, or temporarily stopped acetage uptake. Qualitative agreement between the predictions of a simple mathematical model of acetate inhibition fitted to differential shake flask data and the observed transient data was surprisingly good.
Protease covalently coupled to porous glass: Preparation and characterization
Authors: Mason R. D. , Detar C. C. , Weetall H. H. 
Published: December 2004

AbstractA microbial protease was immobilized by covalent attachment, to porous glass. This material was characterized for pH optimum, thermal stability, and operational half–life using casein as substrate.The immobilized enzyme was used for preparation of soya hydrolysates, low in free amino acids with high solubility.
Hydrolysis of particulate tributyrin in a fluidized lipase reactor
Authors: Lieberman R. B. , Ollis D. F. 
Published: December 2004

AbstractPancreatic lipase has been immobilized onto stainless steel beads by adsorption followed by crosslinking, and onto polyacrylamide by covalent bonding. The activities of the two types of immobilized enzyme toward the particulate substrate, tributyrin emulsion droplets, were determined experimentally, and rate constants based on Michaelis‐Menten kinetics were calculated. The activity of the stainless steel–lipase was determined for various flow conditions and for various support sizes by the use of a differential fluidized bed recycle reactor. The rate constants calculated indicate that the experimental reaction rate is free from mass transfer influences, since the observed Michaelis constant does not vary with the fluidization velocity or with the support particle size. In addition, the Michaelis constant of the stainless steel–lipase was found to be equal to that of the free enzyme, suggesting that adsorption and subsequent crosslinking does not alter the enzyme–substrate affinity. The emulsion substrate mass transfer rates, calculated from the filtration theory, indicate that each substrate particle which contacts the immobilized enzyme is hydrolyzed to a significant extent. Theexperimentally determined kinetic rate constants may be used directly to predict the size of integral fluidized bed reactors.
Analysis of double‐substrate limited growth
Authors: Bader F. G. 
Published: December 2004

AbstractMathematical models which relate the growth rate of a microorganism to a single limiting substrate concentration have long been established. In recent years, it has become apparent that, under certain conditions, the growth rate of an organism may be simultaneously limited by two or more substrates. Mathematical models of double‐substrate limitation fall into two categories: interactive and no interactive models. A discussion of both types of models is presented in both conceptual and mathematical terms. An analogous case of an enzyme which requires two different substrates to produce a single product is presented. This enzyme analog indicates that both types of double‐substrate limitation models appear to be feasible under certain conditions. Based upon stoichiometry and specific growth rate‐substrate concentration contour plots, a method for determining the operational conditions which will lead to double‐substrate limitation is presented.
Preparation of immobilized soybean β‐amylase on porous cellulose beads and continuous maltose production
Authors: Maeda Hidekatsu , Tsao George T. , Chen Li Fu 
Published: December 2004

AbstractImmobilized soybean β‐amylase was prepared by using porous cellulose beads. The expressed activity of the β‐amylase–cellulose beads conjugated below 35 mesh was 59–69% of the initial activity and the protein content was 10–13%. General properties of the conjugate were almost identical with those of the native enzyme except for the Km value. The Km value of the conjugate was 40mM and the Km value of the native enzyme was 0.6mM. This large difference was probably caused by pore structure, i.e., a pore diffusion problem. The film diffusion problem occurred at the flow rate below a linear velocity of 3 cm/min. Maximum maltose contents of the hydrolyzates prepared by the conjugate and the native enzyme were 69 and 71%, respectively. After a continuous column operation at 50°C for 17 days, the activity of the column was 60% of the activity. The half‐life of the column at 40°C was 40 days.