bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics and control of continuous microbial propagators to subject substrate inhibition
Authors: Edwards Victor H. , Ko Raphael C. , Balogh Stephan A. 
Published: December 2004

AbstractInhibitory substrate levels are common in industrial fermentations and in biological waste‐water treatment of many industrial wastes. Continuous microbial cultures are unstable to certain disturbances, such as shock loading by inhibitory substrates. Two feedback proportional control strategies are analyzed and compared for a simple model culture assumed represent able by the culture concentrations of biomass and a single rate‐limiting and growth‐limiting nutrient (substrate). One control strategy, the well known turbidostat, consists of adjusting culture holding time (e.g., by flow rate adjustment) in response to deviations in turbidity or some other measure of culture biomass concentration. The other control strategy is to adjust holding time in response to deviations in limiting nutrient concentrations in the culture. This second control strategy, termed the nutristat, can be superior to the turbidostat in many applications. The sign and magnitude of the dimensionless group {(X/YD)[dμ/dS]s}, is shown to be an important determinant, in the behavior of the open loop and the two closed loop processes. This characteristic group is positive when the specific growth rate is increased by increases in the nutrient concentration, zero when the growth rate is unaffected by the nutrient concentration, and negative in the presence of nutrient or substrate inhibition.The effects of process modifications and of modeling assumptions on the control of the process are discussed and more sophisticated control schemes are also proposed.
Utilization of organic nitrogen compounds by Hydrogenomonas eutropha
Authors: Wixom Robert L. , Sheng Yung‐Boo , Becker Richard S. 
Published: December 2004

AbstractThe chemolithotroph, Hydrogenomonas eutropha, was tested for its ability to utilize a variety of single nitrogen sources during growth in an atmosphere of H2O2CO2 The present data show that H. eutropha can utilize the nitrogen from many, but not all, amino acids, several sulfur‐containing amino acids, glucosamine, and two aliphatic amides. The nitrogen concentration that supported maximum growth for NH4Cl, L‐glutamate, L‐glutamine, urea, and glycine was in the 0.010–0.019M range. H. eutropha failed to remove the nitrogen from primary and secondary amines, eycloleucine, tert‐DL‐leucine, DL‐p‐fluorophenylalanine, DL‐5‐methyltryptophan, creatine, and creatine. This microorganism was able to partially degrade at least six substituted indoles and/or tryptophan catabolites and six substituted imidazoles and/or histidine catabolites. All of a series of 17 dipeptides were able to serve as a nitrogen source for growth in the absence of NH4Cl. Extracts of H. eutropha were able to catalyze the hydrolysis of 16 α‐dipeptides, 2 tripetides, a tetrapeptide, a polypeptide, a β‐aspartyl peptide, 2 γ‐glutamyl peptides, a N‐acetyl amino acid, and 4 amino acid amides. These results emphasize the effectiveness of H. eutropha in utilizing a wide diversity of organic nitrogenous compounds containing amino and amide groups, heterocyclic rings, and peptide bonds.
Kinetics of the xanthan fermentation
Authors: Moraine R. A. , Rogovin P. 
Published: December 2004

AbstractXanthan gum, a heteropolysaccharide with unusual and useful properties, is now produced commercially by fermentation with Xanthomonas compestris NRRL B–1459 in a medium containing glucose, minerals, and a complex nitrogen source—distillers' dried solubles (DDS). Understanding the kinetics of the fermentation should contribute to process improvements and increase the market potential for the gum. Earlier studies showed that although DDS determined initial growth rate, growth was stopped by some mechanism other than substrate exhaustion, probably an effect related to product formation.Product formation did not require active growth, but its rate increased with cell concentration. Specific product formation rate declined at high viscosities. Varying glucose concentration from 0.5 to 5.0% and dissolved O2 tension between 20 and 90% air saturated had no effect on the rates, but pH had to be maintained near 7 and temperature near 28°C to permit continued product formation. Xanthan yield could be explained by the energy required for growth and polymerization, that energy coming from dissimilation of the part of the carbohydrate substrate not converted to polymer.
A mathematical model of the nutrient dynamics of phytoplankton in a nitrate‐limited environment
Authors: Grenney William J. , Bella David A. , Curl Herbert C. 
Published: December 2004

AbstractInsofar as saturation kinetics are applicable to the growth of phytoplankton in laboratory experiments and to growth in nature, the computer modeling of intracellular nutrient partitioning in populations of cells can lead to better understanding of the dynamics of natural populations.A three‐compartment mathematical model was developed to represent a phytoplankton population having the capability to store nitrogen in a nitrate‐limited environment. Parameters were estimated by fitting the model to data from two chemostat experiments reported by Caperon (1968). The model was used to simulate growth dynamics observed in chemostat and batch experiments. The model demonstrated the changes which may occur in the nitrogenous constituents of a phytoplankton population with time and environmental conditions. The model also demonstrates three phenomena which have been observed in field and laboratory experiments but which are not represented by the customary Monod model: (1) uptake rates may significantly exceed not growth rates, (2) high growth rates may be encountered at very low environmental nitrate concentrations, and (3) the ratio of internal nitrogen to population size may change significantly during a study period. It is suggested that the amount of nitorgen in storage may be used as an indicator of the physiological state of a monospecific population.Parameters for the one‐compartment Monod model were estimated by customary methods form data generated by the three‐compartment model. It was shown that difficulties encountered in estimating the yield coefficient and the decay coefficient may be attributed to the intracellular storage phenomenon. It was also demonstrated that the one‐compartment Monod model was inadequate to accurately represent population growth in chemostat experiments when intracellular storage is a significant factor.
Cell growth and extracellular enzyme synthesis in fermentations
Authors: Van Dedem G. , Moo‐Young M. 
Published: December 2004

AbstractThe synthesis of extracellular enzymes by microorganisms frequently occurs under genetic control. A simple two‐parameter model is developed describing the degree of repression or induction in fermentation media.The case of substrate utilization by an extracellular enzyme was analyzed for a vegetable oil‐lipase‐yeast system. It is shown that fatty acids released by the lipase may accumulate in the early stage of growth and exert an influence on the limiting after which relatively little repression or induction takes place.Expressions are also derived for growth and extracellular enzyme synthesis in single‐and multistage continuous cultures. When the cells grow on a directly available soluble substrate, the specific enzyme synthesis is maximal at low dilution rates in the case of repression and at high dilution rates in the case of induction. If the substrate is not directly available, a single continuous stirred tank reactor stage may not be sufficient for efficient substrate utilization; for fermentation processes where an insoluble has to be broken down before the cells can assimilate it, a plug flow type fermentor rather than a mixed chemostat may prove more satisfactory.
Mass transfer and biochemical reaction with semipermeable microcapsules
Authors: Mogensen A. O. , Vieth W. R. 
Published: December 2004

AbstractEnzymes can be encapsulated within a semipermeable membrane which allows reactants to enter and the products to diffuse out. The mass transport from the external fluid to the membrane and the combined mass transport and biochemical reaction from the membrane inwards can be modeled with recognized formulations; measurements of the overall reaction rate lead then to estimates of the permeability of the membrane itself.With capsules enclosing catalase, the permeability of collodion membranes to H2O2 is found to be large (<2 × 10−2cm/sec) in comparison to rates in the other two diffusion zones. For this first‐order reaction system, an analytical solution to the transient case of the well‐stirred finite bath is found using the Laplace transform. With capsules enclosing urease, the nonlinear Michaelis‐Menten kinetics apply to the enzymatic step. The steady‐state operation of a column packed with urease microcapsules is analyzed with the aid of numerical computation and the membrane permeability for urea is found to be 10−3cm/sec.
An apparatus to measure the rate of oxygen evolution while maintaining pO2 constant during photosynthetic growth in closed culture vessels capable of operation at increased hydrostatic pressures
Authors: Pope D. H. , Berger L. R. 
Published: December 2004

AbstractA double polarographic device is described which permits regulation of dissolved oxygen concentration at any preset pO2 in suspensions or cultures of photosynthetic algae. It also simultaneously permits measurements of the rate of oxygen evolution during photosynthesis. The apparatus is designed to operate in closed vessels in the absence of a gas phase, and may be used at increased pressures tested up to 500 atmospheres. Regulation of oxygen levels was maintained constant at various preset concentrations equivalent to atmospheric pO2 values ranging between 0.02 and 0.21 at 25°C.
Immunochemical characterization of commercial protease products
Authors: Hodson P. H. , Scharpf L. G. 
Published: December 2004

AbstractTotal protease activity at pH 7 and 10.3 of 23 commercial grade enzymes was determined. The type and amount of enzymatic activity varied widely among the products. The wide variation in pH 7.0/pH 10.3 proteolytic activity ratios among products indicated that the products studied contained differing levels of alkaline and neutral proteases.Antisera were prepared against the purified enzyme in detergent grade Enzyme AP, neutral protease from B. megaterium, detergent grade ALK Enzyme, and Thermolysin. The commercial (unpurified) products were classified as neutral subtilopeptidase A and subtilopeptidase B from three Bacillus species using these antisera.It was concluded that standard immunochemical techniques provide rapid and sensitive methods for the preliminary identification of sources and types of proteases present in commercial enzyme products.
Phospholipase‐C from Bacillus cereus: Production, purification, and properties
Authors: Shiloach J. , Bauer S. , Vlodavsky I. , Selinger Z. 
Published: December 2004

AbstractA substrain of Bacillus cereus 569/H produced under controlled fermentation conditions in a pilot plant fermentor phospholipase‐C. A partially purified preparation showed good storage stability as a lyophylized powder and in frozen solutions. The preparation contained very small amounts of phosphomonoesterase and proteolytic activities and essentially no ribonuclease activity. The level of hemolytic activity of the preparation was much lower than that of a commercial preparation of phospholipase‐C from Clostridium. Treatment of sarcoplasmic reticulum membrane with phospholipase‐C from B. cereus and from Clostridium showed that the B. cereus enzyme caused hydrolysis of 96% of the membrane phospholipids whereas the enzyme from Clostridium could hydrolyze only 80% of the phospholipids.
Evaluation of ultrafiltration membranes with biological macromolecules
Authors: Hancher C. W. , Ryon A. D. 
Published: December 2004

AbstractEighteen ultrafiltration membranes ranging in molecular weight cutoff ratings from 500 to 300,000 were tested with water, 0.5M NaCl solution, and, in some cases, with macromolecules and urea in a 3‐in. stirred filter cell. Approximately half of the membranes showed a significant decrease in filtration rate during the first 24‐hr period. The steady‐state rates were less than the manufacturers' rating for about two thirds of the membranes, the discrepancy being greater for the membranes with high molecular weight cutoffs.The filtration rates were linearly dependent on applied pressure over the range at least as great as 15 to 55 psig. The rate decreased as the concentration of macromolecules such as transfer ribonucleic acid (tRNA) increased; the rate for a concentration of 3 mg tRNA/per ml was one‐fourth of that observed when no tRNA was present. Some increase in rate (∼33 to 50%) was obtained by increasing the stirring speed from 100 rpm to 1000 rpm.The membranes were effective for desalting and concentration of macromolecules but not for separation of large molecules from each other, such as tRNA from bovine serum albumin. Easily denatured molecules such as catalase were not deactivated by filtration at 4°C.
Oxygen absorption in stirred tanks: A correlation for ionic strength effects
Authors: Robinson Campbell W. , Wilke Charles R. 
Published: December 2004

AbstractA new correlation is given for the prediction of the volumetric coefficient for mass transfer (KLa) in stirred tanks from dispersed gas bubbles to basal salt solutions of ionic strengths representative of fermentation media. The correlation includes the effects of both the operating parameters (agitation power per unit volume and gas superficial velocity) and the physicochemical properties of the system: interfacial tension, viscosity, density, diffusion, coefficient and, in particular, ionic strength. The effect of the latter was found to be most significant in the Newtonian systems of water‐like viscosity investigated; no previous correlations have included the effect of ionic strength. KLa values were determined by using a dissolved oxygen probe to monitor the steady‐state oxygen tension in continuous flow experiments, and/or the rate of change of oxygen tension in unsteady‐state semibatch experiments. In the latter cases, results were computed by a nonlinear, least squares computer program which fitted the experimental data to a model of probe transient response characteristics. The general applicability of the model and the computational procedure was verified by comparing the results to those obtained with the same electrolyte solution in the steady‐state mode. The experiments were run over a wide range of agitation power inputs, including those typical of both soluble‐ and insoluble‐substrate fermentations. The correlation appears to be valid for both oxygen mass transfer with and without homogeneous chemical reaction in the liquid phase; in the former case, for example, sulfite oxidation, knowledge of the chemical reaction enhancement factor is required. In addition to predicting oxygen transfer capabilities, the correlation may be used for other sparingly soluble gases of interest in fermentation systems, such as methane, hydrogen, and carbon dioxide.
Production of microbial protein from waste cellulose by Thermomonospora fusca, a thermophilic actinomycete
Authors: Crawford Don L. , McCoy Elizabeth , Harkin John M. , Jones Paula 
Published: December 2004

AbstractThe growth characteristics of Thermomonospora fusca, a cellulolytic thermophilic actinomycete, are described in terms of growth on pulping fines, a cellulosic waste of the paper industry. A fermentation was developed which substantially degrades this waste, with the residual product of growth containing about 30% microbial protein. This protein, as shown by a preliminary feeding study with baby chicks and by amino acid analyses, appears to be of good nutritional quality and contains no strongly toxic materials. The extracellular cellulolytic enzymes present in the spent broth are discussed in relation to their potential recovery as a by‐product of the fermentation, as is also the possible use of the fermentation as a waste disposal system.
Mixing by impeller agitation in continuous flow systems containing polysaccharide solutions
Authors: Johnson D. N. , Hubbard D. W. 
Published: December 2004

AbstractSystem response data for step changes in input tracer concentration have been obtained for two different impeller agitated continuous flow mixing systems containing aqueous polysaccharide solutions. The vessel volumes were 1.6 and 10.9 liters. Polysaccharide concentration, dilution rate, and impeller speed were varied according to a plan devised using dimensional analysis and assuming that bulk motion is the predominant mass transport mechanism in the system. The data show that this is not true and that serious errors may occur if scale‐up calculations are based on assuming that bulk motion predominates. Under the operating conditions used, perfect mixing was not observed.
Application of an insolubilized hepatic microsomal drug oxidase to the continous production of N‐oxides
Authors: Sofer Samir S. , Ziegler Daniel M. , Popovich Robert P. 
Published: December 2004

AbstractThe optimum operating temperature and pH have been determined for a catalyst prepared by the insolubilization of a hepatic microsomal mixed‐function oxidase on glass beads. Temperature is a more significant variable than pH in determining potential catalyst yield (total product/unit catalyst). An operating range of about 25–28°C is optimal with respect to catalyst life at pH 7.6. Like the purified soluble oxidase, the glass bead‐mounted enzyme catalyzes the NADPH‐ and oxygen‐dependent oxidation of a variety of amines, hydrazines, and thioureylenes. The catalyst has been used in a simple slurry reactor to prepare mg quantities of N‐oxide metabolites of prochlorperazine, guanethidine, and ethylmorphine.
High‐yield growth of E. coli at different temperatures in a bench scale fermentor
Authors: Shiloach J. , Bauer S. 
Published: December 2004

AbstractE. coli wax grown exponentially at different temperatures in a bench scale fermentor. pH was maintained at 6.8 by ammonia which served also as the nitrogen source. Glucose was introduced semi‐continuously at a predetermined rate which ensured a glucose concentration of 25–50 g/liter during growth. The culture was sparged with pure oxygen.Yield constants for glucose, nitrogen, phosphorus, and oxygen were determined at the different temperatures of propagation.When all growth conditions, except temperature, were kept constant, the maximal possible yield of exponentially grown cell mass was found to be directly proportional to the doubling time. Concentrations of up to 55 g dry cells/liter culture were achieved.
Kinetics of substrate inhibition of exponential yeast growth
Authors: Jackson Jay V. , Edwards Victor H. 
Published: December 2004

AbstractThis work concerns mathematical modeling of the rate of microbial growth on inhibitory levels of nutrients as affected by pH, concentration of the nutrients, temperature, cultivation method, and method of data analysis. Candida utilis (ATCC 9226) was grown with sodium acetate as growth‐limiting carbon and energy source in mineral salts medium in shake flask and continuous cultures to study inhibition by excess acetate. Differential shake flask cultures were grown at low yeast concentrations at temperatures (T) of 25 and 30°C, pH's between 5.5 and 7.0, and acetate concentrations (S) between 0.25 and 3.0% (w/v). Growth data were exponential with correlation coefficients greater than 0.995 in 49 of 56 experiments; the lowest correlation coefficient was 0.986. Specific growth rates (μ) determined by graphical methods showed only fair correlation with those determined by regression analysis. Both sets of specific growth rate data were grouped at constant T and pH and fitted to the three parameter equation,

The improvement in use of the fitted equation instead of the mean value was significant with greater than 70% confidence in all (14 groups) and 90% confidence in only half of the data groups; the correlation does not improve with the increasing acetate inhibition at lower pH. Both defects in the model and insufficient data at each pH are responsible. A modified six parameters with hydrogen ion concentration(H+) as follows:

Specific growth rates calculated with the six parameter equation matched observed values in all groups of isothermal data better than the means with greater than 99% confidence. The six parameter model adequately represents effects of acetate and hydrogen ion concentrations under constant or slowly changing environmental conditions and balanced growth; although better models probably exist. Thus steady‐stste and transient continuous culture experiments agreed with many published growth yields, but specific growth rates could only be predicted qualitatively from the model fit to the shake flask data. The data and present models could be incorporated into published models for transient growth at low nutrient concentrations to correlate and perhaps predict microbial growth kinetics over a much wider range of growth conditions than now possible.
Continuous lactic acid fermentation of whey to produce a ruminant feed supplement high in crude protein
Authors: Keller A. Kent , Gerhardt Philipp 
Published: December 2004

AbstractA mathematical model was developed to simulate, on a digital computer, the continuous fermentation of whey lactose to lactic acid with neutralization by ammonia. The simulation predicted the retention times for experimental test and the use of two stages for greatest efficiency. In the experimental tests, Lactobacillus bulgaricus was inoculated into whey in a 14‐liter continuous fermentor at 44°C and with automatic pH control. A series of steady‐state conditions was managed nonaseptically for 42 days without evident contamination and with an actual increase in the efficiency of conversion. Lactic acid was produced predominately' throughout the period, with less than 0.2% of other compounds. The product contained approximately 8 times as much crude protein (N × 6.25) as the original whey. In a single‐stage fermentation at pH 5.5, a retention time of 15 hr resulted in a residual lactose concentration of 0.7%; and little improvement was realized by increasing the retention time. Increasing the pH to 5.8 resulted in a significant improvement, but further increasing the pH to 6.0 resulted in only a small additional gain. By the employment of two fermentors in series at pH 5.5 with a total retention time of 31 hr, the residual lactose was reduced to less than 0.1%. Lactic acid was produced as a function mainly of maintenance rather than growth metabolism.
A multigroup model for predator‐prey interactions
Authors: Villarreal Ernesto , Canale Raymond P. , Akcasu Ziya 
Published: December 2004

AbstractThe predator‐prey interactions between the protozoan Tetrahymena pyriformis and the bacterium Aerobacter aerogenes have been studied experimentally and mathematically. A mathematical model for the ciliates defines the mass distribution of cells within the population. The resulting model equations are solved by the use of multigroup theory. Experimental data from batch and continuous flow reactors are compared with the results of the numerical integration.
Adsorption of amyloglucosidase on inorganic carriers
Authors: Solomon B. , Levin Y. 
Published: December 2004

AbstractA simple method for immobilizing amyloglucosidase by adsorption on inorganic carriers is described. Amyloglucosidase was adsorbed on acid‐activated molecular sieve and on alumina. The immobilized enzyme preparations exhibited 50–100% of the initial activity and possessed high temperature stability. A prolonged working life span was achieved, which could possibly satisfy requirements for industrial application.