bluuebunny/crossref_metadata_2025 huggingface dataset:
Adsorption and recovery of cellulases during hydrolysis of newspaper
Authors: Castanon Maris , Wilke Charles R.
Published: December 2004

The adsorption of cellulases from Trichoderma viride was studied during the hydrolysis of newspaper. By measuring individual enzyme activities it was found that in the early stage of hydrolysis enzyme components showing CxA; were adsorbed preferentially to those showing C1A; afterwards ths situation was inverted. Electrophoretic resolution of proteins in hydrolysates showed a continuous decrease of enzyme proteins in solution, and furthermore suggested that the enzymes once adsorbed remained immobilized on the substrate (even after extensive digestion). Experiments to recover the enzyme that had remained in solution after typical hydrolysis showed a potential saving of up to 40%.
Growth and composition of Escherichia coli subjected to square‐wave perturbations in nutrient supply: Effect of varying amplitudes
Authors: Pickett A. M. , Bazin M. J. , Topiwala H. H.
Published: December 2004

The effect of regular variations in the input limiting nutrient concentration at different cycle amplitudes on the growth and composition (elemental and macromolecular) of Escherichia coli ML30 in chemostat culture is described. The cycle time was maintained constant at 2.0 hr. The basal level of nutrient fed to cultures was also maintained constant but the concentration amplitude was varied over a range from 0.2 to 5.0 g/liter. A lag between the stimulus and organisms response was observed and found to be independent of cycle amplitude over most of the range examined. Increasing the cycle amplitude did not effect the cell yield from glucose or the elemental composition of the organisms. However, large variations in the macromolecular composition of the cells (on a dry weight basis) were found; at 4.0 g/liter amplitude the cells contained some 82% protein. The relevance of this type of reactor operation in large‐scale fermentations is discussed.
Microcalorimetry of microorganism metabolism of monosaccharides and simple aromatic compounds
Authors: Lovrien Rex , Jorgenson Gregg , Ma Maggie K. , Sund Wesley E.
Published: December 2004

Heat conduction solution enable rapid determination of the heats of aerobic and anaerobic metabolism of substrate by microorganisms. Aliquots of 1.0 ml cell suspension, 5 × 109 cell/ml, were mixed with a few dozen nmol substrate contained in 0.5 ml, under a controlled atmosphere of air, O2, or N2. At these substrate concentration, with adapted microorganisms, metabolism and its heat generation are usually complete within 300 to 600 sec. The raw data yield ΔHapp values. The ΔHapp were determined in the range 0.001 to 0.010% substrate, and extrapolated (limit substrate concentration →0), to yield Δ0H̄, the limiting differential molar heat of metabolism. The Δ0H̄ values express the heat generated when there is rapid metabolism but little new growth, minimal contribution by H+ transfer from metabolites, and maintenance of aerobicity or anaerobicity as specified. Escherichiacoli B/5 was used for aerobic and anaerobic combustion of eight sugars. Pseudomonas multivorans, and an Acinetobacter, strain B‐1, were used for aerobic metabolism of benzene, toluene, naphthalene, and a methylnaphthalene. The larger heats of combustion of the hydrocarbons enable the use of aqueous solutions of hydrocarbons well below their solubility limits. The quotient Δ0H̄/n (n = atoms carbon/molecule substrate) varies from (‐)36 to (‐)67 kcal/mol carbon for the sugars. The most reduced sugar yields the largest exothermic heats. The quotient varies from (‐)27 to (‐)81 kcal/mol carbon for the aromatic hydrocarbons. Comparison of the calorimetric heats of metabolism of those from total aerobic combustion in aquo (where available) give measure of the efficiencies with which the heat contents of the aqueous substrate are used by the bacteria.
Bacillus sphaericus for the control of mosquitoes
Authors: Singer S.
Published: December 2004

From 1972 to 1977 a large laboratory effort was devoted to determining data on efficacy, safety, environmental impact (on nontarget organisms), and some preliminary field work using several isolates of Bacillus sphaericus. The B. sphaericus strains were found to be specific in their mosquito larvicidal activity, not causing mammalian toxicity nor apparent perturbation of the environment. During this period several fermentation and industrialization problems were investigated so that by 1978, using new strains and cultures, it was possible to have prepared kilogram amounts of an active dry stable powder, of strain 1593, for field evaluation. These field evolution. These field evaluations are presently still in progress. Control has been seen particularly against Culex, Anopheles, and Psorophora species, with some what less control aganst Aedes species. Unlike the agriculturally oriented Bacillus thuringiensis candidates, B. sphaericus bacterial cell, which is digested in the larval midgut (within a peritrophic membrane), releasing a toxin as early as 15 min after ingestion. Subsequent death of the larva ensues. Recent evidence suggests that applied B. sphaericus powder will survive in aquatic situations (ditches, ponds, and tree holes) for at least nine month. Comparisons of the B. sphaeicus strains with recently isolated strains of B. thuringiensis (var. israelensis), the latter being particularly active against Aedes species, indicates that they may be useful complements of each other in overall mosquito control strategies. The recent isolation of several new strains of B. thuringiensis, from WHO‐CCBC accessions from Roumania, indicate that although the B. thuringiensis isolate is a rare event when compared to the occurrence of B. sphaericus isolates (they usually occur together in accessions from which B. thuringiensis is isolated), several new useful strains of B. thuringiensis should be anticipated. The longevity of the B. thuringiensis strains in the wild has not yet been investigated.
Application of temperature‐sensitive mutants for single‐cell protein production
Authors: Miyasaka Yuichiro , Rha Chokyun , Sinskey Anthony J.
Published: December 2004

Cell‐division‐cycle, temperature‐sensitive mutants of Saccharomyces cerevisiae were investigated as a means of altering the morphological characteristics and subsequent physical properties of single‐cell protein (SCP). Strain 4471, harboring mutation cdc 4, formed a visible complex mass at the nonpermissive temperature, after being grown at 30°C and then transferred to 37°C for 8 hr. Microscopic observation showed that the mother cell was unable to complete the budding process at the nonpermissive temperature, which caused the cells to enlarge. Viscosity measurements were used to establish and characterize optimum morphological changes in the yeast. The Maximum increase in viscosity occurred when cells were incubated at 30°C and then shifted to 37°C for 8 hr. Strain 4471 exhibited yield stress, whereas A364A did not. Maximum change in yield stress occurred when cells were shifted from 30 to 37°C for 8 hr. No significant loss of protein or RNA occurred in strain 4471, as compared to strain A364A, when incubated at the nonpermissive temperature.
Model of steady‐state‐biofilm kinetics
Authors: Rittmann Bruce E. , McCarty Perry L.
Published: December 2004

A steady‐state biofilm is defined as one that has neither net growth nor decay over time. The model, developed for steady‐state‐biofilm kinetics with a single substrate, couples the flux of substrate into a biofilm to the mass (or thickness) of biofilm that would exist at steady‐state for a given bulk substrate concentration. Based on kinetic and energetic constraints, this model predicts for a single substrate that a steady‐state bulk concentration, Smin, exists below which a steady‐state biofilm cannot exist. Thus, in the absence of adsorption of bacteria from the bulk water and for substrate concentration below Smin, substrate flux and biofilm thickness are zero. Equations are provided for calculating the steady‐state substrate flux and biofilm thickness for S greater than Smin. An example is provided to demonstrate the use of the steadystate model.
Application of macroscopic principles to microbial metabolism
Authors: Roels J. A.
Published: December 2004

General 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

A 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

The 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

The 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

Detritiation 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

Protein 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

Saccharomyces 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

The 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

The 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

Culture 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

The 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

The 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

Further 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

The 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

The 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

The 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

The 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

Pulsing 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

A 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.
A kinetic expression for hydrolysis of soluble starch by glucoamylase
Authors: Kusunoki Koichiro , Kawakami Koei , Shiraishi Fumihide , Kato Keiichi , Kai Mayumi
Published: December 2004

As the hydrolysis of starch by glucoamylase proceeds with stepwise removal of glucose units from the nonreducing ends of the starch chain, the number of available substrate molecules is essentially unchanged in the course of the degradation. In view of this aspect, a simple practical kinetic expression, which consists of a modified Michaelis–Menten form with product inhibition, is presented for the hydrolysis of soluble starch. It is assumed that the values of kinetic parameters Vm and Km vary linearly from the values for starch toward those for maltose. The applicability of this kinetic expression is verified through the simulation with the experimental results for the hydrolysis of two soluble starches with different average molecular weights of 3 × 104 and 3 × 106.
Enhancement of starch conversion efficiency with free and immobilized pullulanase and α‐1,4‐glucosidase
Authors: Ram Kumar A. , Venkatasubramanian K.
Published: December 2004

Glucoamylase and pullulanase were immobilized on reconstituted bovine‐hide collagen membranes using the covalent azide linkage method. A pretanning step was incorporated into the immobilization procedure to enable the support matrix to resist proteolytic activity while accommodating an operating temperature of 50°C. The immobilized glucoamylase and pullulanase activities were 0.91 and 0.022 mg dextrose equivalent (DE) min−1 cm−2 of membrane, respectively. Immobilized glucoamylase had a half‐life of 50 days while the immobilized pullulanase had a half‐life of 7 days. This is a considerably improved stability over that reported by other researchers. The enzymes were studied in their free and immobilized forms on a variety of starch substrates including waxy maize, a material which contains 80% α‐1–6‐glucosidic linkages. Substrate concentrations ranged from 1% to a typical commercial concentration of 30%. Conversion efficiencies of 90–92% DE were obtained with free and immobilized glucoamylase preparations. Conversion enhancements of 4–5 mg of DE above this level were obtained by the use of pullulanase in its free or immobilized forms. Close examination of free pullulanase stability as a function of pH indicated improved thermal stability at higher pH values. At 50°C and pH 5.0, the free enzyme was inactivated after 24 h. At pH 7.0, the enzyme still possessed one‐half its activity after 72 h. Studies were conducted in both batch and continuous total recycle reactors. All experiments were conducted at 50°C. Experiments conducted with coimmobilized enzymes proved quite promising. Levels of conversion equivalent to those obtained with the individually immobilized enzymes were realized.
The mechanism of uranium biosorption by Rhizopus arrhizus
Authors: Tsezos M. , Volesky B.
Published: December 2004

Biosorption of elements is a little understood phenomenon exhibited by some types of even nonliving microbial biomass. A common fungus Rhizopus arrhizus has been reported to take up uranium from aqueous solutions to the extent of 180 mg U6+/g. The mechanism of uranium sequestering by this type of biomass was studied by using experimental techniques such as electron microscopy, x‐ray energy dispersion analysis, IR spectroscopy, and supporting evidence was obtained for a biosorption mechanism consisting of at least three processes. Uranium coordination and adsorption in the cell‐wall chitin structure occur simultaneously and rapidly whereas precipitation of uranylhydroxide within the chitin microcrystalline cell‐wall structure takes place at a lower rate. Interference of Fe2+ and Zn2+ coions with uranium biosorption is indicated.
Oxygen mass transfer into aerated CMC solutions in a bubble column
Authors: Deckwer W.‐D. , Nguyen‐Tien K. , Schumpe A. , Serpemen Y.
Published: December 2004

Differing findings on the volumetric mass transfer coefficients kLa in CMC solutions in bubble column bioreactors have been reported in the literature. Therefore, oxygen mass transfer was studied again in CMC solutions in a 14‐cm‐i.d. × 270‐cm‐height bubble column using different spargers. The kLa values were determined along with the dispersion coefficients by fitting the prediction of the axial dispersed plug model with the experimental oxygen concentration profiles in the liquid phase. Surprisingly, the obtained liquid phase dispersion coefficients for CMC solution are higher than one would expect from correlations. The kLa data depend largely on the flow regime. In general, they are lower than those reported in the literature. The data for developing slug and established slug flow are dependent on the gas velocity and the effective viscosity of the solution and can br correlated by a simple correlation. This correlation describes kLa values measured on fermentation broth of Penicillium chrysogenum with striking agreement.
Recycle in fermentation processes
Authors: Hamer G.
Published: December 2004

Until recently, the recycle of the solid (microbial), liquid, or gaseous phases in microbiological processes has only been practiced rarely, with the notable exception of activated sludge processes for wastewater treatment, where recycling of a large fraction of the microbial phase is essential for process stability and performance. During the last decade, the economic impact of a number of politically motivated changes with respect to energy and feedstock costs and availability, and legislation directed towards markedly higher levels of environmental protection have encouraged the evaluation and subsequent development of recycle technology in the fermentation industry. Many of the developments have occurred in isolation and some have failed to result in either an improvement in process economics or any reduction in the quantity of pollutants discharged. This article seeks to review the present diversity of approaches to recycle technology in fermentation processes in order to provide a sensible basis for future developments.
Hydrodynamic stress capacity of microorganisms
Authors: Bronnenmeier R. , Märkl H.
Published: December 2004

A new experimental method has been developed for estimating the hydrodynamic stress capacity of microorganisms. In a test apparatus, stable continuous cultures of three types of green algae and two cyanobacteria were exposed to well‐defined hydrodynamic loads in a free jet. During and after the stress experiments the cultures showed a different response due to the damage in the jet. The results of these free‐jet experiments with short stress exposure were compared to those of stirring experiments in which hydrodynamic load was continuously generated by a stirrer. In both kinds of experiments distinct critical stress values could be determined below which no essential damage of the microorganisms cultures occurred. A correlation between the critical stress values in free‐jet and stirring experiments was found. It can be deduced that the free‐jet data, expressed as critical volumetric dissipated energy, are suitable for the calculation of hydrodynamic stress to which microorganisms might be exposed in biotechnical plants without suffering damage.
Carbon limitation of biomass production in high‐rate oxidation ponds
Authors: Azov Y. , Shelef G. , Moraine R.
Published: December 2004

Theoretical considerations confirmed by outdoor experiments indicated carbon limitation of biomass production in high‐rate oxidation ponds at certain seasonal and operational conditions. Apparently, free carbon dioxide concentration in the pond is the major determinant of carbonlimiting algal photosynthesis. High concentrations of free CO2 are provided through bacterial respiration which is the main contributor to algal photosynthesis. At high photosynthetic activities and low organic loadings, free CO2 concentrations are low; its flux into algal cells determines photosynthesis and biomass production rate in the pond.
Film diffusional influences on the kinetic parameters in packed‐bed immobilized enzyme reactors
Authors: Patwardhan V. S. , Karanth N. G.
Published: December 2004

A number of studies on packed‐bed immobilized enzyme reactors have shown the significant influence of the external film mass transfer resistance on the apparent kinetic parameters. Some of the earlier mathematical models using approximation techniques have attempted to explain the linearity of the S0x vs ln (1 − x) plots observed experimentally for systems obeying Michaelis–Menten kinetics. However, there has been no critical examination of the bounds of validity of the approximations used. Further, the situations where the above linearity is not valid have been examined neither conceptually nor quantitatively. The work presented here overcomes these drawbacks of the earlier analyses by approaching the problem from a different angle. Methods of evaluation of the intrinsic kinetic parameters under different experimental situations have been outlined and illustrated with several examples.
Accumulation of heavy metals in unicellular algae
Authors: Khummongkol D. , Canterford G. S. , Fryer C.
Published: December 2004

A model for metal uptake by microorganisms based on surface adsorption has been developed, and then applied to the uptake of cadmium by Chlorella vulgaris. A linear equilibrium relationship between metal in the solution and that adsorbed on the cell surface is assumed and confirmed at low cadmium concentrations by short‐term uptake experiments. When it incorporates a description of cell growth, the model predicts an initial rapid uptake and a subsequent slow uptake. Such behavior has often been observed in experiments with growing microorganisms. This indicates that the slow uptake, sometimes thought to be active or metabolic, could be due to the simultaneous effects of growth and surface adsorption. The model shows that initial metal uptake is fast and approaches equilibrium within a few seconds. This prediction is in agreement with experimental results in a batch system: Equilibrium is reached before the first samples are taken (at 10 min) and there is then no measurable change until growth provides a significant increase in cell surface (after several hours). Thus the equilibrium constant can be calculated from experimental results of uptake at 10 min. The equilibrium is found to be affected by phosphate concentration; the amount of cadmium adsorbed on the cell decreases as the concentration of phosphate is increased. Long‐term uptake experiments in growing cultures show a greater metal accumulation than predicted by the adsorption model, suggesting the involvement in the slow long‐term uptake of some mechanism other than adsorption. This is confirmed by experiments in which uptake in cultures exposed to cadmium throughout the growth period is compared with short‐term uptake in similar cultures grown in the absence of cadmium. The modeling approach to metal adsorption provides a basis for further development. A model combining description of adsorption and of intracellular accumulation is necessary to provide a more complete description. Such a model, with precise definitions of system parameters and means of evaluating these parameters from experimental results, will be a powerful tool in investigation of metal uptake by microorganisms.
Diffusion and the limiting substrate in two‐substrate immobilized enzyme systems
Authors: Leypoldt John K. , Gough David A.
Published: December 2004

The effects of mass transport resistances on two‐substrate immobilized enzyme systems are investigated theoretically. It is shown that the effects of mass transport resistances on the overall reaction rate are related mainly to the transport of the limiting substrate. In the absence of external mass transport resistances, the limiting substrate can be identified by knowing only the ratio of the bulk substrate concentrations, the permeability of the support to the two substrates, and the stoichiometry of the reaction. However, a combination of internal and external mass transport resistances may result in the other substrate becoming limiting. These effects are most significant when the mass transport resistances are high. Applications in the design of enzyme electrodes and chemical reactors are discussed.
Preparation and properties of fibrinolytic enzymes produced by Cochliobolus lunatus
Authors: Abdel‐Fattah Ahmed F. , Ismail Abdel Mohsen S.
Published: December 2004

Some properties of the crude lyophilized fibrinolytic enzyme produced by Cochliobolus lunatus in surface culture were studied. Enzyme concentrations over the range from 0.16 to 10.16 mg/mL showed that concentration above a certain level ceased to be the limiting factor controlling enzyme action. At pH 6.8 and a temperature of 40°C, the fibrinolytic enzyme showed maximal activity at a human fibrin concentration of 2 mg/mL. The optimum pH values for enzyme activity were 6.98 and 7.0, using Sørensen and Mcllvaine buffers, respectively. Fibrinolytic enzymes were isolated from a static culture of Cochliobolus lunatus; isolation was carried out with various agents. Ammonium sulphate yielded the highest recovered fibrinolytic activity. The fraction salted out by precipitation at 25% ammonium sulphate saturation possessed the highest recovered fibrinolytic activity compared to the ammonium sulphate, ethanol, and acetone fractions.
Effect of dissolved oxygen on nitrogen fixation by A. vinelandii. I. Free cell cultures
Authors: DiLuccio Robert C. , Kirwan Donald J.
Published: December 2004

As part of an investigation into the use of biological nitrogen fixation for fertilizer ammonia production, continuous culture studies of respiration and nitrogen fixation in the aerobic bacteria Azotobacter vinelandii under oxygen‐limited conditions were conducted. Respiration and growth rates followed Monod forms with respect to dissolved oxygen concentration. However, specific nitrogen fixation rate and nitrogenase activity exhibited maximum values at dissolved oxygen concentrations of ca. 0.02 mM (10% of air saturation). These results suggest careful control of oxygen in the environment is necessary to optimize fixed nitrogen production by this organism.
Environmental parameters influencing phenolics production by batch cultures of Nicotiana tabacum
Authors: Sahai O. P. , Shuler M. L.
Published: December 2004

The influence of temperature, illumination, hormonal levels (2,4‐D and kinetin), carbon to nitrogen ratios, antibiotics, and precursor feeding on phenolics production by Nicotiana tabacum (tobacco) was studied. This plant cell system was chosen as a model system to learn more about secondary product formation in plant cell tissue cultures. This is the first study to manipulate all of these environmental parameters with a single plant cell system. The most striking results were with 2,4‐D manipulation. The removal of 2,4‐D resulted in significant phenolics production during the stationary phase, while normal levels strongly suppressed phenolics production during the stationary phase. The addition of phenylalanine stimulated phenolics production per gram of cells but strongly inhibited growth.
Practical reactor systems for yeast cell immobilization using biomass support particles
Authors: Black G. M. , Webb C. , Matthews T. M. , Atkinson B.
Published: December 2004

The technique of cell immobilization using porous support particles (biomass support particles) has been successfully applied to yeast cells. Two reactor configurations exploiting the use of these particles have been developed and assessed for use in aseptic yeast fermentations. A liquid‐fluidized bed fermenter has been devised for use with particles denser than the fermentation liquor whilst a gas‐stirred circulating bed fermenter proved suitable for particles of essentially neutral buoyancy. Both systems have been operated successfully for extended periods of continuous operation. The utilization of biomass support particle technology in such reactors provides a practical and robust system for immobilized cell reactors. This technology offers significant opportunities for further development.