bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of macroscopic principles to microbial metabolism
Authors: Roels J. A. 
Published: December 2004

AbstractGeneral expressions for mass, elemental, energy, and entropy balances are derived and applied to microbial growth and product formation. The state of the art of the application of elemental balances to aerobic and heterotrophic growth is reviewed and extended somewhat to include the majority of the cases commonly encountered in biotechnology. The degree of reduction concept is extended to include nitrogen sources other than ammonia. The relationship between a number of accepted measures for the comparison of substrate yields is investigated. The theory is illustrated using a generalized correlation for oxygen yield data. The stoichiometry of anaerobic product formation is briefly treated, a limit to the maximum carbon conservation in product is derived, using the concept of elemental balance. In the treatment of growth energetics the correct statement of the second law of thermodynamics for growing organisms is emphasized. For aerobic heterotrophic growth the concept of thermodynamic efficiency is used to formulate a limit the substrate yield can never surpass. It is combined with a limit due to the fact that the maximum carbon conservation in biomass can obviously never surpass unity. It is shown that growth on substrates of a low degree of reduction is energy limited, for substrates of a high degree of reduction carbon limitation takes over. Based on a literature review concerning yield data some semiempirical notions useful for a preliminary evolution of aerobic heterotrophic growth are developed. The thermodynamic efficiency definition is completed by two other efficiency measures, which allow derivation of simple equations for oxygen consumption and heat production. The range of validity of the constancy of the rate of heat production to the rate of oxygen consumption is analyzed using these efficiency measures. The energetic of anaerobic growth are treated—it is shown that an approximate analysis in terms of an enthalpy balance is not valid for this case, the evaluation of the efficiency of growth has to be based on Gibbs free energy changes. A preliminary analysis shows the existence of regularities concerning the free energy conservation on anaerobic growth. The treatment is extended to include the effect of growth rate by the introduction of a linear relationship for substrate consumption. Aerobic and anaerobic growth are discussed using this relationship. A correlation useful in judging the potentialities for improvement in anaerobic product formation processes is derived. Finally the relevance of macroscopic principles to the modeling of bioengineering systems is discussed.
Dialysis continuous process for ammonium lactate fermentation: Simulated and experimental dialysate‐feed, immobilized‐cell systems
Authors: Stieber R. W. , Gerhardt Philipp 
Published: December 2004

AbstractA generalized mathematical model, previously developed and experimentally validated, was modified and used to computer‐simulate two dialysate‐feed systems for operating a dialysis continuous process for the ammonium lactate fermentation. The simulations predicted that the feeding of substrate into the dialysate circuit and thence into the fermentor circuit via dialysis should greatly improve the production of cell mass and metabolite product. Experiments were conducted to test the system in which the fermentor is operated without an effluent, thus immobilizing the cells. Dried cheese whey ultrafiltrate was rehydrated to contain a normal concentration of lactose (62 mg/ml), supplemented with yeast with an adapted culture of Lactobacillus bulgaricus. The system was operated without interruption for 26 days. Results during steady‐state conditions showed that the system is a new and useful way to immobilize living cells for the purpose of producing a metabolite at a high rate for a prolonged time. The substrate consumed by the cells is converted to product via maintenance metabolism only and is sterilized by dialysis.
Optimization of operating temperature for continuous glucose isomerase reactor system
Authors: Park Sun Ho , Lee Sun Bok , Ryu Dewey D. Y. 
Published: December 2004

AbstractThe Optimal temperature control policy for an immobilized glucose isomerase reactor system was studied. This optimization study takes into consideration the enzyme deactivation during the continuous reactor operation. The Kinetic parameters including reduced Michaelis–Menten constant (K̄m), reduced maximum reaction rate (V̄m), equilibrium constant (Ke), and enzyme deactivation constant (kd) and their functional relationships to temperature were determined experimentally. The optimization problem was formulated in terms of maximization of fructose productivity as the objective function. The optimization problem was solved by making use of a maximum principle and the control vector iteration method. Approximately optimal temperature control policy was employed as compared with the reactor operation at an optimum constant temperature.
Effects of the surfactant tween 80 on enzymatic hydrolysis of newspaper
Authors: Castanon Marisi , Wilke Charle R. 
Published: December 2004

AbstractThe effects of Tween 80 on the enzymatic hydrolysis of newspaper were tested. By monitoring sugar production it was found that the surfactant (0.1%) increased the rate and extent of cellulose saccharification. Consequently, the rate of enzyme usage in the hydrolysis reactor was improved by 33%. In addition, in the presence of surfactant the recovery of enzymes was higher. Analysis of the enzyme solution showed that with Tween 80 present larger fractions of enzyme remained in solution throughout hydrolysis. Thus, it appears that the surfactant hindered the immobilization of the enzymes on the substrates by reducing the strength of adsorption.
Application of immobilized hydrogenase for the detritiation of water
Authors: Klibanov Alexander M. , Huber Jonathan 
Published: December 2004

AbstractDetritiation of contaminated water is an essential part of nuclear power production. Most promising methods used for this process are based on catalyzed hydrogen isotope exchange reactions. It is proposed herein to replace the platinum catalysts which are currently used in industry with immobilized hydrogenase. Whole bacterial cells of Alcaligenes eutrophus immobilized in calcium alginate or κ‐carrageenan gels were found to be efficient catalysts of the reaction of hydrogen–tritium (H–T) exchange in both a batch tank reactor and in a column. The dependence of the reaction rate on the amount of immobilized cells in the system, and on the concentration of the cells in the matrix, indicate that enzymatic H–T exchange is not controlled by diffusion. Immobilized A. eutrophus cells are enzymatically active over a wide range of pH, with a broad maximum from pH 6.0 to 8.0, and are quite resistant to inhibitors of hydrogenases such as O2 and CO. Upon increasing the temperature from 4 to 37°C, the rate of hydrogenase‐catalyzed H–T exchange increases by a factor of 5. From the standpoint of catalytic efficiency, 1 g of PtO2 is approximately equivalent to 10 g of cells (wet weight). In contrast of platinum‐based catalysts, bacterial hydrogenases (1) are potentially inexpensive; (2) can be readily available in bulk quantities; (3) are maximally active in liquid water.
Effect of cultural factors on cellulase activity and protein production by Aspergillus terreus
Authors: Garg S. K. , Neelakantan S. 
Published: December 2004

AbstractProtein production by Aspergillus terreus GN1 grown on 1.0% alkali‐treated bagasse was studied under various cultural conditions. The maximum biomass protein content of 20.1% and protein recovery of 11.2% was obtained with an initial pH of 4.0, with 1/5 (v/v) inoculum in continuously shaken cultures grown for seven days. Protein content of the alkali‐treated bagasse was 3.0%. Highest crude protein percent also corresponded with highest carboxymethyl cellulase and filter paper enzyme activities.
The production of ethanol by immobilized yeast cells
Authors: Williams David , Munnecke Douglas M. 
Published: December 2004

AbstractSaccharomyces cerevisiae cells were immobilized in calcium alginate beads for use in the continuous production of ethanol. Yeasts were grown in medium supplemented with ethanol to selectively screen for a culture which showed the greatest tolerance to ethanol inhibition. Yeast beads were produced from a yeast slurry containing 1.5% alginate (w/v) which was added as drops to 0.05M CaCl2 solution. To determine their optimum fermentation parameters, ethanol production using glucose as a substrate was monitored in batch systems at varying physiological conditions (temperature, pH, ethanol concentration), cell densities, and gel concentration. The data obtained were compared to optimum free cell ethanol fermentation parameters. The immobilized yeast cells examined in a packed‐bed reactor system operated under optimized parameters derived from batch‐immobilized yeast cell experiments. Ethanol production rates, as well as residual sugar concentration were monitored at different feedstock flow rates.
Enhanced production of cellulase, hemicellulase, and β‐glucosidase by Trichoderma reesei (Rut C‐30)
Authors: Tangnu S. Kishen , Blanch Harvey W. , Wilke Charles R. 
Published: December 2004

AbstractThe Production of cellulases and Hemicellulases was studied with Trichoderma reesei Rut C‐30, This organism produced, together with high cellulase activities, considerable amounts of xylanases and β‐glucosidase. Three cellulose concentration (1, 2.5, and 5.0%) were examined to determined the maximum levels of cellulase activity obtainable in submerged culture. Temperature and pH profiling was used to increase cell mass to maximum levels within two days and thereby enhancing fermentor productivity at higher substrate levels. The effect of temperature, pH, Tween‐80 concentration, carbon sources, and substrate concentration on the ration of mycelial growth and extracellulose enzyme production are described.
Effect of intraparticle diffusion resistance on apparent stability of immobilized enzymes
Authors: Ooshima Hiroshi , Harano Yoshio 
Published: December 2004

AbstractThe effect of the intraparticle diffusion resistance on the apparent stability of the immobilized enzyme suffering from the first‐order deactivation has been studied quantitatively. A general expression for the relationship between the decreasing observed enzymatic reaction rate and the intrinsic enzyme deactivation rate has been introduced. The method to estimate the intrinsic deactivation rate constant also has been proposed. Using the invertases immobilized on a anion‐exchange resin, the theory proposed in this work has been verified experimentally.
Enzymatic hydrolysis of cellulose: Evaluation of cellulase culture filtrates under use conditions
Authors: Mandels Mary , Medeiros John E. , Andreotti Raymond E. , Bissett Frank H. 
Published: December 2004

AbstractCulture filtrates from three mutant strains of Trichoderma reesei grown on lactose and on cellulose were compared under use conditions on four cellulose substrates. Cellulose culture filtrates contained five to six times as much cellulase as lactose culture filtrates. Unconcentrated cellulose culture filtrates produced up to 10% sugar solutions from 15% cellulose in 24 h. Specific activity in enzyme assays and efficiency in saccharification tests were low for enzymes from all the mutants. Over a wide range the percent saccharification of a substrate in a given times was directly proportional to the logarithm of the ratio of initial concentrations of enzyme and substrate. As a result of this, dilute enzyme is more efficient than concentrated enzyme, but if high sugar concentrations are desired, very large quantities of enzyme are required. Since the slopes of these plots varied, the relative activity of cellulase on different substrates may be affected by enzyme concentration.
Estimation of heats of combustion of biomass from elemental analysis using available electron concepts
Authors: Patel Snehal A. , Erickson L. E. 
Published: December 2004

AbstractThe method of Thornton and Dulong's formula for estimating heats of combustion are compared in this work. Heats of combustion predicted by Thornton's method for renewable resources such as wood, straw, and municipal solid wastes are considerably closer to experimentally measured values compared to values predicted by Dulong's formula. Thornton's method states that the heat of combustion is directly proportional to the quantity of oxygen consumed in the combustion process. A method which utilizes the weight fraction carbon on a dry basis and the reluctance degree to predict the heat of combustion of renewable resources is presented.
Flow characteristics of a pilot‐scale airlift fermentor
Authors: Mercer Donald G. 
Published: December 2004

AbstractThe effects of aeration on the flow characteristics of water in a glass pilot‐scale airlift fermentor have been examined. The 55‐L capacity fermentor consisted of a 15.2‐cm‐i.d. riser column with a 5.1‐cm‐i.d. downcomer tube. It was found that the average bubble size diminished with increased aeration. Typically, average bubble sizes ranged from 4.32 mm at a superficial gas velocity of 0.64 cm/s to 1.92 mm at 10.3 cm/s. A gas holdup of 0.19 was attained with superficial gas velocities (vs) on the order of 10 cm/s, indicating the highly gassed nature of the fluid in the riser section of the fermentor. Circulation velocities of markers placed in the fermentor decreased with increasing aeration rates due to increased turbulence and axial liquid back mixing within the riser section. Actual volumetric liquid circulation rates remained relatively constant (0.36–0.49 L/s) for values of (vs) up to 10 cm/s. Based on theoretical calculations, the ascending velocity of bubbles in a swarm reached 54 cm/s in the range of (vs) values studied.
Further purification and characterization of a thermophilic rennet
Authors: Laxer Shoshana , Pnsky Alex , Bartoov Benjamin 
Published: December 2004

AbstractFurther work on a thermophilic rennet synthesized by a thermophilic actinomycete is reported. It was produced by growth in fermentor of 50‐or‐200‐L volume and was purified by membrane filtration of a cell‐free supernatant and then molecular filtration and ion exchange chromatography. Its stability under various conditions was determined: The enzyme is a true rennet requiring calcium ions for activity. Experiment shows that it resembles neither pepsin, trypsin, nor chymotrypsin. It is freeze‐labile with a molecular weight of 9700 from amino acid composition. When skim milk powder was added to the growth medium, a rennet with different properties was obtained.
Performance of fluidized‐bed reactors utilizing magnetic fields
Authors: Sada Eizo , Katoh Shigeo , Shiozawa Masami , Fukui Tsunehiko 
Published: December 2004

AbstractThe performance of fluidized‐bed reactors utilizing a magnetic field was determined by the use of magnetite‐containing beads of immobilized unease. The reactors showed similar or higher conversions in comparison with fixed‐bed reactors, although some aggregation of the beads in the magnetic field was observed. No effusion of the beads occurred up to a flow rate of 24 cm/min.
Alcohol precipitation of proteins: The relationship of denaturation and precipitation for catalase
Authors: Schubert Paul F. , Finn Robert K. 
Published: December 2004

AbstractThe precipitation of crude beef liver catalase at 4°C by the lower alcohols could be correlated in a manner analogous to that used for salting out precipitations with ammonium sulfate. At high alcohol concentrations, however, the analogy breaks down since denaturation effects must betaken into account Depending upon the concentration of the alcohol and temperature, the denaturation transition may be either thermally induced or solvent induced. When the precipitated enzyme was redissolved in buffer, not all forms could refold spontaneously to a catalytically active conformation. The data on the precipitation yields of catalase correlated well with denaturation diagrams previously developed. Thus, a quantitative basis could be established to relate the sensitive performance of the technique to the experimental conditions. A further correlation between the amino‐acid composition of the enzyme and the optimal concentration of alcohol required for precipitation may provide a guide for the extension of this work to other systems.
A study of producing ethanol from cellulose using Clostridium thermocellum
Authors: Zertuche Leticia , Zall Robert R. 
Published: December 2004

AbstractThe feasibility of producing ethanol in a continuous system from cellulose using Clostridirrrn thermocellum was investigated. This anaerobic and therniophilic bacterium was able to degrade cellulose directly into ethanol with acetic acid, hydrogen. and carbon dioxide as by‐products of this fermentation. The fermentation was first carried out in a batch mode to study the effects of buffers, temperature, and agitation on microbial growth and ethanol production. From the compounds used to control pH. sodium bicarbonate had the most preferred effects on generation time and ethanol production. As expected, there was a positive relationship between temperature and growth rate. On the other hand, agitation did not benefit from ethanol production or microbial growth. The possibility of noncompetitive inhibition within such a system was deduced from the calculation of the kinetic constants Km and Vmax. Continuous fermentations were carried out at 60°C and pH 7.0 using 1.5 and 3% pure cellulose as a limiting substrate. The maximum ethanol concentration reached during the 1.5% cellulose fermentation was 0.3%. and 0.9% during the 3% cellulose fermentation. The yield of ethanol was about 0.3 grams per gram of consumed cellulose. The overall yield in both schemes was around 0.45 and 0.75 grams per gram of cellulose degraded. It was concluded that cellulose could be degraded continuously in a system with C. thermocellum for production of ethanol. While the continuous system like the batch method is feasible, it may not be promising as yet because of the slow generation time of this microorganism.
Effect of nutritional factors on cellulase enzyme and microbial protein production by Aspergillus terreus and its evaluation
Authors: Garg S. K. , Neelakantan S. 
Published: December 2004

AbstractThe biomass yield, cellulolytic activity, and protein recovery using Aspergillus terreus GN1 with alkali‐treated sugarcane bagasse was studied using different levels (250–600 mg of N/L of broth) of organic and inorganic nitrogen sources. e.g., cattle urine, urea, cornsteep liquor, ammonium sulfate, ammonium nitrate, ammonium iron sulfate, ammonium chloride, and sodium nitrate. Among different levels of alkali‐treated bagasse substrate concentrations (0.5–4.0% w/v) tested, 1.0% substrate yielded the highest crude protein content, protein recovery, and cellulolytic activity. The biomass recovery with 1.0% substrate ranged from 290–380 mg/500 mg bagasse substrate in a 50‐mL broth with a nitrogen level of 250–600 mg of N/L in all the sources except ammonium iron sulfate, which yielded 402–439 mg/500 mg bagasse substrate. However, crude protein content of biomass obtained with an ammonium iron sulfate nitrogen source was the lowest. Cornsteep liquor nitrogen source at the rate of 600 mg of N/L yielded the maximum crude protein of 32.9%, protein recovery of 22.2 g/100 g of bagasse, and carboxymethyl cellulase and filter paper enzyme activities of 1.1 and 0.09 units/mL, among the organic and inorganic nitrogen sources studied. In general, the organic nitrogen sources and inorganic nonammonium nitrogen sources were utilized preferentially for protein production over the inorganic ammonium nitrogen sources. The fermentation time required under optimum cultural and nutritional conditions for A. terreus GN1 was also evaluated. The crude protein content of the biomass increased gradually up to the seventh day of fermentation, but the protein recovery rate was high up to two or three days. It was observed that the cellulose utilization rate increased after an initial lag of one day up to the third day and gradually increased further, which corresponded positively with protein content, biomass protein recovery, and cellulase enzyme activity. On the seventh day of fermentation, the crude protein content, biomass protein recovery, water‐soluble carbohydrate, bagasse cellulose utilization, CMCase, and FPase activities were 32.8%, 20.1 g/100 g of bagasse, 6.2%, 82.7%, 1.0. and 0.08 U/mL, respectively. The final biomass recovered contained 32.8% crude protein content and had an in vitro rumen digestibility (IVRD) coefficient of 68.8%. The biomass contained almost all the essential and nonessential amino acids and was comparable with FAO reference protein. It is concluded that a fermentation time of 72 h gave a faster rate of protein production of 16.9 g/100 g of bagasse with 69.8% bagasse cellulose utilization with 76.0% IVRD. and contained almost all the essential and nonessential amino acids.
Measurements and models of synchronous growth of fission yeast induced by temperature oscillations
Authors: Agar David W. , Bailey James E. 
Published: December 2004

AbstractPulsing of temperature in a fermentor at intervals coincident with cell generation time was used to induce synchrony in a population of the fission yeast Schizosaccharomyces pombe. Measurements of culture protein, RNA, and DNA during synchronous growth confirm continuous synthesis of protein and RNA and discontinuos synthesis of DNA as previously reported. Flow microfluorometry of populations at different times during the synchrony cycle was used to monitor the changes in single‐cell protein. RNA, and DNA frequency functions. These measurements illustrate very clearly the degree of synchrony and patterns of macromolecular synthesis and also confirm previous estimates of the cellular protein contents characteristic of dividing cells. Additional insights into single‐cell kinetics and division controls are provided by two‐parameter flow microfluorometry measurements and by mathematical modeling of population dynamics. Such data are necessary foundations for robust population balance models of microbial processes.
Characterization and evaluation of Aspergillus oryzae lactase coupled to a regenerable support
Authors: Friend B. A. , Shahani K. M. 
Published: December 2004

AbstractA derivative of crosslinked Sepharose, p‐(N‐acetyl‐L‐tyrosine azo) benzamidoethyl‐CL‐Sepharose 4B, was synthesized and used for the selective immobilization of thermostable lactase from Aspergillus oryzae.Preparations of soluble and immobilized lactase were evaluated under initial velocity conditions in a batch process. Immobilization had no significant effect on the pH optimum at 50°C or kinetic parameters at pH 4.5 or pH 6.5 and 50°C. At pH 4.5, the soluble enzyme possessed maximum activity at 60°C and the immobilized at 55°C; at pH 6.5 both showed maximum activity at 55°C. The activation energy, entropy, and enthalpy decreased significantly with immobilization at pH 4.5 but not at pH 6.5. When the immobilized enzyme was placed in a packed‐bed reactor, the effect of temperature on activity was altered as reflected by a marked decrease in the thermodynamic parameters of activation at both pH levels. Upon immobilization there was also a dramatic increase in the apparent thermal stability of the lactase, and the mean half‐life at 50°C was increased from 7.2 to 13 days at pH 4.5 and from 3.8 to 16 days at pH 6.5.