bluuebunny/crossref_metadata_2025 huggingface dataset:
Production of SCP and cellulase by Aspergillus terreus from bagasse substrate
Authors: Garg S. K. , Neelakantan S.
Published: December 2004

The fermentation of 1.0% untreated bagasse under optimum cultural and nutritional conditions with Aspergillus terreus GN1 indicated that the maximum rate of protein and cellulase production could be obtained during three days of submerged fermentation. Even though 16.4% protein recovery, 0.55 units CMCase/mL, and 0.027 FPase units/mL were obtained on the seventh day, the rates of increase in protein recovery and cellulase production were slower than those obtained up to these days, which were 14.3% protein recovery, 0.45 units CMCase/mL, and 0.019 units FPase/mL. There was an initial lag in the utilization of cellulose up to two days due to the utilization of the water‐soluble carbohydrate present in untreated bagasse. Cellulose utilization and water‐soluble carbohydrate content during fermentation were correlated with protein recovery and enzyme production. The protein and cellulase production during three days fermentation with 1.0% untreated and treated bagasse were compared and the protein content of the total biomass was calculated and treated bagasse were compared and the protein content of the biomass was calculated into constituent protein contributed by the fungal mycelium and the under graded bagasse. The total biomass recovered with untreated and treated bagasse was 1020 and 820 mg/g bagasse substrate, respectively, and contained 14.3 and 20.6% crude protein, respectively. The contribution of fungal biomass and under graded bagasse was 309 and 711, and 373 and 447 mg/g untreated and treated bagasse substrates, respectively. In an 8‐L‐flask trial during three days of fermentation, the recovery of SCP and cellulase were 66 g and 32,400 units (Sigma) for treated bagasse and 82 g and 8200 units (Sigma) for untreated bagasse, respectively.
On the mechanism of immobilized glucose oxidase deactivation by hydrogen peroxide
Authors: Malikkides Christakis O. , Weiland Ralph H.
Published: December 2004

The result of experiments in a fixed‐bed reactor containing glucose oxidase immobilized on a nonporous support and conducted in the absence of diffusional limitations are reported. Kinetic parameters were established by separate batch experiments. The key observation was that, in every case, poisoning by product hydrogen peroxide resulted in a minimum in enzyme activity in the interior of the bed, well away from the ends. The deactivation data were interpreted by fitting the rate constant for poisoning, the only free parameter, to a previously reported theory. The theory postulates several deactivation mechanisms each of which leads to self‐consistent kinetics, but the only mechanism which fitted the data assumes that peroxide attack the enzyme when it is the from complexed with glucose. Theory and experiment agreed to within the accuracy (± 2%) of the activity measurements.
Removal rates of bacterial cells from glass surfaces by fluid shear
Authors: Powell Martin S. , Slater Nigel K. H.
Published: December 2004

A simple kinetic relationship is proposed to model the rate of removal of bacterial cells from solid surface by a shearing force. The theory is compared to experimentally obtained data for the removal of B. cereus cells from glass capillaries, the shear being imparted by a the flow of medium through the capillary. The critical shear stress required to sterilize the capillary wall is obtained experimentally for a number of industrial contaminant bacteria. The effect of settling time on critical shear stress is also investigated.
On the role of reversible denaturation (unfolding) in the irreversible thermal inactivation of enzymes
Authors: Zale Stephen E. , Klibanov Alexander M.
Published: December 2004

The contribution of the reversible thermal unfolding of an enzyme toward the overall irreversible thermoinactivation process has been examined both theoretically and experimentally. Using bovine pancreatic ribonuclease as a model, we have studied the effect of such variables as pH and salts both on the equilibrium constant of reversible denaturation and on the rate constant of the overall irreversible process. It has been demonstrated that at temperatures where a significant fraction of the enzyme molecules are in the native conformation, there is a correlation between the enzyme thermostabilities with respect to the reversible and irreversible inactivations: greater stability against the former is accompanied by greater stability against the latter. On the other hand, at very high temperatures (where essentially all of the enzyme molecules are unfolded), such a correlation does not exist. These findings are considered in terms of a kinetic model for irreversible enzyme thermoinactivation, and the implications of the derived relationship are discussed.
Ethanol from whey: Continuous fermentation with cell recycle
Authors: Janssens J. H. , Bernard A. , Bailey R. B.
Published: December 2004

The production of ethanol from cheese whey lactose has been demonstrated using a single‐stage continuous culture fermentation with 100% cell recycle. In a two‐step process, an aerobic fed batch operation was used initially to allow biomass buildup in the absence of inhibitory ethanol concentrations. In the anaerobic ethanol‐producing second step, a strain of Kluyveromyces fragilis selected on the basis of batch fermentation data had a maximum productivity of 7.1 g ethanol/L/h at a dilution rate of 0.15 h−1, while achieving the goal of zero residual sugar concentration. The fermentation productivity diminished when the feed sugar concentation exceeded 120 g/L despite the inclusion of a lipid mixture previous shown to enhance batch fermentation productivities.
Multistage continuous culture to examine secondary metabolite formation in plant cells: Phenolics from Nicotiana tabacum
Authors: Sahai O. P. , Shuler M. L.
Published: December 2004

The feasibility of operating a multistage continuous culture of plant cells was demonstrated for Nicotiana tabacum. Cells in the second stage of a two‐stage chemostat were morphologically distinct from cells in the first stage or cells in a single‐stage unit with a holding time equal to the combined holding times in the two‐stage system. Cells in the second stage produced much higher levels of phenolics per unit weight of cells than cells in either the first‐stage or single‐stage unit. The steady‐state was reproduced. When a glucose side stream was fed to the second stage, an increase in apparent cell division was observed with a simultaneous decrease in phenolics productivity. When the toxic precursor phenylalanine was pulsed into the reactor, the quantity of biomass decreased temporarily while phenolic productivity increased. These experiments demonstrate that multistage continuous culture may be useful in increasing secondary metabolite formation in cells and in exploring mechanisms controlling secondary metabolite formation.
Algal autoflocculation—verification and proposed mechanism
Authors: Sukenik A. , Shelef G.
Published: December 2004

Biomass autoflocculation in outdoor algal cultures was found to be associated with increases of culture pH levels, due to CO2 consumption by the algal photosynthetic activity. Under these alkaline conditions, some medium chemical ions precipitated together with the algal biomass. The chemical substances involved with the process and its dependence on pH value were studied by simulation of autoflocculation in laboratory experiments. Proper concentrations of calcium and orthophosphate ions in the medium are important for autoflocculation and, in order to attain it within the pH range 8.5–9.0, the culture should contain 0.1mM–0.2mM orthophosphate and 1.5mM–2.5mM calcium prior to raising the pH level. Calcium phosphate precipitates are considered as the flocculating agent which reacts with the negatively charged surface of the algae and promotes aggregation and flocculation.
Kinetics of the enzymatic hydrolysis of cellulose
Authors: Wald Stephen , Wilke Charles R. , Blanch Harvey W.
Published: December 2004

Enzymatic hydrolysis of cellulose for sugar production offers advantages of higher conversion, minimal by‐product formation, low energy requirements, and mild operating conditions over other chemical conversions. The development of a kinetic model, based on observable, macroscopic properties of the overall system, is helpful in design and economic evaluation of processes for sugar conversion and ethanol production. A kinetic model is presented, incorporating enzyme adsorption, product inhibition, and considers a multiple enzyme and substrate system. This model was capable of simulating saccharification of a lignocellulosic material, rice straw, at high substrate (up to 333 g/L) and enzyme concentrations (up to 9.2 FPU/mL) that are common to proposed process designs.
Ethanol production by Zymomonas mobilis in fed‐batch fermentations
Authors: Silman R. W.
Published: December 2004

The production of ethanol by Zymomonas mobilis NRRL B‐4286 was studied in fed‐batch cultures. Initial percent (w/v) glucose, rate of feed, and quantity of 50%; (w/v) glucose feed were varied. Glucose inhibition of growth rate occurred at concentrations greater than 8% (w/) Feed was begun after 4 h incubation. Feed volume was ca. 36%; of starting batch volume to get ca. 10%; (w/v) ethanol at harvest. The range of feed rates studied varied from 16%; batch volume/h (glucose concentration increased to an inhibitory level) to 4%; batch volume/h (glucose concentration dropped rapidly to zero and was limiting). Increasing feed volume to 46%; of starting volume at the best feed rate (ca. 10%; feed volume/h) increased final ethanol concentration to 11.3%; (w/v). However, the resultant increase in fermentation time from ca. 21 to 29 h decreased ethanol volumetric productivity from 5.2 to 4.6 g/L h.
Development of a continuous process for metal accumulation by Zoogloea ramigera
Authors: Norberg Anders , Rydin Stefan
Published: December 2004

Biomass, mainly consisting of an acidic polysaccharide produced by Zoogloea ramigera, has been used as an adsorbing agent in a continuous process for the recovery of metal. The adsorption of copper has been studied with respect to retention time, biomass concentration, and reaction pH, in order to determine the optimal conditions for copper recovery. The results indicate that the uptake of copper is rapid and efficient. About 0.17 g Cu is adsorbed per gram of biomass within 10 min. At high biomass concentrations, the total amount of copper removed from solution is high, but the specific amount of copper adsorbed to biomass is low. The biomass exhibits a higher adsorptive uptake at low concentrations.
A new modeling technique and computer simulation of bacterial growth
Authors: Papageorgakopoulou H. , Maier Walter J.
Published: December 2004

A mathematical model that describes substrate utilization and cell growth in terms of two potentially rate‐limiting enzyme systems has been developed. Consideration of substrate inhibition and enzyme repression have been incorporated. The model provides a rational approach for characterizing non‐steady‐state phenomena. The model has been used to analyze batch test data to illustrate the effects of inhibition, repression, and concurrent substrate utilization. Its utility lies in the fact that it provides a quantitative framework for describing changes in the activity levels of cells that result from changes in substrate concentration and/or substrate type. The lag phase resulting from exposure to a new substrate can be modeled.
The Production ofL‐serine with a methylotrophic microorganism using theL‐serine pathway and coupling with anL‐tryptophan‐producing process
Authors: Behrendt U. , Bang W. G. , Wagner F.
Published: December 2004

The cultural conditions for the production of enhanced formation of L‐serine (up to 7 g/L) are described with the methylotrophic bacteriumPseudomonas3 ab (DSM 672). The batch process is divided into three parts: (1) the biomass production phase, (2) substrate limitation period, and (3) L‐serine accumulation phase. The initial specific production rate ofqp= 0.1 g L‐serine/g dry wt/h is based on the inhibition of the L‐serine pathway. This is accomplished by high precursor concentrations (glycine) and a pH shift to pH 8.5. The enzymatic background is discussed. Furthermore, a coupling of the L‐serine process with a L‐tryptophan‐producing process is demonstrated.
Alcoholic fermentation of raw cassava starch by Rhizopus koji without cooking
Authors: Fujio Yusaku , Suyanadona Puangpen , Attasampunna Poonsook , Ueda Seinosuke
Published: December 2004

Using only wheat bran koji from the Rhizopus strain, raw cassava starch and cassava pellets converted reasonably well to alcohol (ethanol) without cooking at 35°C and pH 4.5–5.0. When the initial broth contained 30 g raw cassava starch, 10 g Rhizopus sp. koji, and 100 mL tap water, 12.1 g of alcohol was recovered by final distillation from fermented broth. In this case, 12.1 g alcohol corresponds to an 85.5% conversion rate based on the theoretical values of the starch content. When the initial broth contained 40 g cassava starch, 14.1 g of alcohol was recovered, where 14.1 g corresponds to a 74.5% conversion rate. The alcoholic fermentation process described in the present work is considered more effective and reasonable than the process using raw starch without cooking reported until now, since the new process makes it unnecessary to add yeast cells and glucoamylase preparation.
Alcoholic fermentation: Modelling based on sole substrate and product measurement
Authors: Bovee J. P. , Strehaiano P. , Goma G. , Sevely Y.
Published: December 2004

Optimal automatic bioreactor control requires a mathematical model adapted to the potency of reliable sensors. A new relationship describing the kinetic behavior of alcoholic fermentation is discussed. By analogy with chemical kinetics, the biological rate of substrate consumption is related to substrate and product concentration by the following equation:

Using the well known yield relation between product and substrate, it is possible to describe in both batch and continuous cultures the ethanol and sugar concentrations versus time. This pattern has been successfully tested on several fermentations performed by yeasts (S. cerevisiae, S. bayanus, and S. cerevisiae sake) and a bacterium (Z. mobilis). This simple relationship is proposed as a tool for process control alcoholic fermentation.
An adaptive control algorithm for fed‐batch culture
Authors: Stanišsis J. , Levišauskas D.
Published: December 2004

The implementation of adaptive control for a fed‐batch culture in order to maximize the output of product based on a self‐adjusting model is discussed in the present work. Optimization methods were applied to the generalized mathematical model of a fed‐batch fermentation process to determine control algorithms that could be used for on‐line process control. The efficiency of the proposed adaptive algorithms was investigated by simulating a model system. The model of amylotytic enzyme fermentation that was proposed by the authors was taken from a real process. Dynamic modelling has shown that the main problem of realization is connected with the on‐line identification of the adaptive model's parameters. To avoid this problem, we have introduced special limitations on the parameters' time variations that increased the convergence of the identification algorithm. The results of the investigation have shown the efficiency of the proposed adaptive algorithms, and the results of this work should be investigated for real process control.
The hydroxylation of biphenyl by Aspergillus toxicarius: Conditions for a bench scale fermentation process
Authors: Golbeck John H. , Cox John C.
Published: December 2004

Fungi of the Aspergillus sp. can hydroxyate biphenyl to 4,4′‐dihydroxybiphenyl, a chemical intermediate used in the plastics industry. The authors studied various batch culture conditions for the production of 4,4′‐dihydroxybiphenyl, by Aspergillus toxicarius, in 25‐mL shake flasks and 2‐L fermenter cultures. Conditions investigated included temperature, aeration, carbon and nitrogen sources, biomass content, and time of substrate addition. Under optimum conditions we observed a rate of 4,4′‐dihydroxybiphenyl production of 15–20 mg/day/g dry wt mycelia. Such a production rate is probably too low to support a commercial process and possible reasons for the low productivity are discussed.
Analysis of a continuous, aerobic, fixed‐film bioreactor. I. Steady‐state behavior
Authors: Park Young , Davis Mark E. , Wallis David A.
Published: December 2004

The analysis of a continuous, aerobic, fixed‐film bioreactor is performed by simulating the behavior of penicillin production in a three‐phase fluidized bed. Rigorous mathematical models are developed for a fluidized‐bed fermentor in which bioparticles are fluidized by the liquid medium and air. The steady‐state performance of the fluidized‐bed reactor is appraised in terms of penicillin productivity and outlet concentration by considering the two extremes in contacting patterns, complete back‐mix and plug flow, in the absence of a growing biofilm. The results show that the complete back‐mix contacting pattern is preferred over that of plug flow due to the nature of the penicillin kinetic relationships. It is also shown that for the dual‐nutrient (glucose and oxygen) penicillin reaction system the optimum biofilm thickness does not equal the penetration depth of a limiting nutrient, but depends upon the total reactor configuration.
Analysis of a continuous, aerobic, fixed‐film bioreactor. II. Dynamic behavior
Authors: Park Young , Davis Mark E. , Wallis David A.
Published: December 2004

The dynamic analysis of a continuous, aerobic, fixed‐film bioreactor has been performed. Rigorous mathematical models have been developed for a fluidized‐bed fermentor with biofilm growth. The transient performance of the reactor is appraised in terms of outlet penicillin concentration for constant, as well as variable carbon substrate feed rates. The effect of the reactor oxygen transfer capacity is elucidated for those cases employing substrate feeding strategies. The results show that penicillin production in a continuous, fixed‐film bioreactor reaches a maximum with processing time, but subsequently decreases as cell mass accumulates and substrate deficiencies occur. The maximum production level can be maintained for increased operating times if the substrate supply is continuously increased. The duration of this prolonged production is a direct function of the rate of increase and the operating time at which the increase is initiated. The oxygen transfer capacity of the reactor was found to be important to the effectiveness of a feeding strategy.
A modified matrix perfusion–microcarrier bead cell culture system. I. Adaptation of the matrix perfusion system for growth of human foreskin fibroblasts
Authors: Strand Janie M. , Quarles John M. , McConnell Stewart
Published: December 2004

Two strains of human foreskin fibroblast cells were incapable of sustained growth in a matrix perfusion culture system, possibly because of their inability to attach to the fiber surfaces. Addition of microcarrier beads to the extracapillary space allowed attaining high cell densities in excess of 107 cells per culture unit. Microcarrier beads were tested in hollow fiber culture devices containing membranes of 104 or 105 D nominal porosities. Best results were obtained when initial cell densities of at least (2–3) × 106 cells were used in units with 105 D pore size membranes and DEAE–Sephadex or polyacryl‐amide microcarrier beads in the extracapillary space. This extension of the matrix perfusion system should be useful for growing other anchorage dependent cells while retaining the advantages of perfusion culture.
Interaction of proteins with Triton X‐100‐substituted sepharose 4B
Authors: Nemat‐Gorgani Mohsen , Karimian Khashayar
Published: December 2004

Interaction of a number of arbitrarily chosen proteins with Triton X‐100‐substituted Sepharose 4B has been investigated. Of the proteins examined, bovine serum albumin, hemoglobin, glutamate dehydrogenase, and pepsin were found immobilized on the adsorbent. Binding of these proteins occurred irrespective of pH and NaCl concentration. Cytochrome c, used as a model protein, was totally immobilized only at low pH. Adsorption of glutamate dehydrogenase and pepsin took place with retention of their catalytic activities. Moreover, glutamate dehydrogenase used as a model allosteric enzyme, was found to retain its native properties upon binding to the adsorbent in the forms of suspension or column. Results are discussed in terms of specific interactions involving the hydrophobic region of Triton X‐100 and the apolar patches or crevices present on the surface of protein molecules. Possible potential of the matrix as a method for preparation of biologically active immobilized proteins and its application in continuous operations are also discussed.
Application of bioenergetics to modelling the microbial conversion of D‐xylose to 2,3‐butanediol
Authors: Jansen Norman B. , Flickinger Michael C. , Tsao George T.
Published: December 2004

During the oxygen limiting growth of Klebsiella oxytoca, the xylose metabolism may be considered as consisting of three components: conversion to 2,3‐butanediol by “fermentation,” oxidation to carbon dioxide by respiration, and assimilation to cell mass. The amount of energy required for the assimilation of cell mass is assumed to determine the extent to which the two energy producing reactions occur. The activity of each energy producing pathway is also determined by the availability of oxygen and by the energy yield of each pathway. These relationships can be quantified by equating the ATP required for growth and maintenance to the ATP produced by the energy producing reactions. The resulting equation for butanediol production appears similar to the Luedeking and Piret model where the parameters α and β are related to the maximum cell yield from ATP and the maintenance energy requirement. These parameters were estimated from 14 batch fermentations, and the resulting simulation was used to describe the effects of the oxygen transfer rate and the initial xylose concentration on the yields and rates of the 2,3‐butanediol fermentation.
Immobilized cyclomaltodextrin glucanotransferase of an alkalophilic Bacillus sp. No. 38‐2
Authors: Kato Takashi , Horikoshi Koki
Published: December 2004

Cyclomaltodextrin glucanotransferase [1,4‐α‐D‐glucan‐4‐α‐D‐(1,4‐α‐D‐glucano)–transferase (cyclizing), E.C.−2.4.1.19] of an alkalophilic Bacillus sp. No. 38‐2 (ATCC 21783), which contains three types of enzymes (acid, neutral, and alkaline enzymes), was immobilized on synthetic adsorption resin. No distinguishing changes in pH or thermal stabilities of enzyme were observed due to the immobilization. Since acid–enzyme activity had disappeared, the optimum pH of immobilized enzyme was 9.0. Optimum temperature for the enzyme activity changed from 50 to 55°C. The enzyme converted starch to cyclodextrins without significant loss of activity under the conditions of continuous reaction for about two weeks by using the column system (60°C at pH 8.0). About 63% of soluble starch solution [4% (w/v)] was changed to cyclodextrins, as tested so far.
Effect of melanin on enzymatic hydrolysis of cellulosic waste
Authors: Ray R. M. , Desai J. D.
Published: December 2004

Wood waste powder from Tectona grandis containing melanin was less susceptible to enzymatic hydrolysis than powder without melanin. About a 53% increase in saccharification was noted when melanin was removed. Melanin caused inhibition to all cellulolytic enzymes, but in different degrees. Endo‐β‐1,4‐glucanase and β‐glucosidase were markedly inhibited when melanin was preincubated with enzyme, while exo‐β‐1,4‐glucanase was severely inhibited when melanin was preincubated with substrate. The latter was found to be dependent on the contact time. The activities of endo‐β‐1,4‐glucanase and β‐glucosidase were noncompetitively inhibited by melanin.
Enzymic saccharification of sugar beet pulp
Authors: Moloney A. P. , O'Rorke A. , Considine P. J. , Coughlan M. P.
Published: December 2004

Culture filtrates of Talaromyces emersonii UCG 208 grown on beet pulp can convert the polysaccharide components of this agricultural waste to soluble sugars. The saccharification process is facilitated if the pulp is milled or incubated with alkali or peracetic acid before addition of enzyme. However, treatment of unmilled pulp with commercial pectinase prior to incubation with Talaromyces filtrate is also very effective; under suitable conditions, complete hydrolysis of total polysaccharides has been achieved.
Degradation of a washed carrot preparation by cellulases and pectinases
Authors: Sreenath H. K. , Frey M. D. , Radola B. J. , Scherz H.
Published: December 2004

A washed carrot substrate, prepared with high yields and easy handling properties, was found to be a suitable substrate for studying cellulolytic and pectinolytic degradation processes. A cellulase from Trichoderma reesei, and Rohament P, a macerating enzyme from Aspergillus alleaceǔs in endopolygalacturonase, degraded the washed carrot substrate to an extent of 60%. With the combined action of both enzymes, degradation was more than 80%. Simultaneous action of both enzymes was more efficient than their sequential use. The effect of temperature, pH, incubation time, enzyme concentration, and substrate concentration on the degradation by the single enzymes and their mixture were studied. Gas chromatographic sugar analysis revealed that Rohament P liberated glucose, arabinose, and galactose in the low‐molecular‐weight fraction obtained by ultrafiltration, in addition to high amounts of galacturonic acid. These carbohydrates were also found in the high‐molecular‐weight fraction (retentate) together with rhamnose and mannose. Cellulase BC released mainly glucose, although galacturonic acid, arabinose, xylose, and mannose were also detected both in the ultrafiltrate and retentate. Morphologically, during Rohament P degradation of the washed carrot substrate, damaged tissues and disintegrated cells were seen, whereas on cellulase BC action mainly disintegrated cell walls were observed.
Sterilization of oils: Data to support the use of a continuous point‐of‐use sterilizer
Authors: Bader F. G. , Boekeloo M. K. , Graham H. E. , Cagle J. W.
Published: December 2004

The continuous slow feed of animal and vegetable oils is frequently found to be an economically attractive method for maintaining antibiotic fermentations at a highly productive rate. The sterilization of oil feeds can present a major problem in the production plant. In this article, we present data and methodology on the kinetics of the thermal sterilization of No. 2 lard oil and soybean oil. It was also determined that dry heat sterilization condition could occur if dry spores were added to dry oil. This condition could only be partially alleviated by the addition of water to the oil. The theory and design of a small tubular coil continuous sterilizer for sterilizing oils at the point of use is also presented. This type of sterilizer is economical and versatile and simplifies control and instrument requirements. It provides a realistic alternative to the use of sterile feed tanks and sterile headers.
Immobilization of enzymes in porous supports: Effects of support–enzyme solution contacting
Authors: Dennis K. E. , Clark D. S. , Bailey J. E. , Cho Y. K. , Park Y. H.
Published: December 2004

Proteins have been immobilized in porous support particles held in a fixed‐bed reactor through which protein solution is continuously circulated. Changing the recirculation flow rate alters the observed immobilization kinetics and the maximum enzyme loading which can be achieved for glucose oxidase and glucoamylase on carbodiimide‐treated activated carbon and for glucoamylase immobilized on CNBr–Sepharose 4B. Direct microscopic examination of FITC‐labelled protein in sectioned Sepharose particles and indirect activity–loading studies with activated carbon–enzyme conjugates all indicate that immobilized enzyme is increasingly localized near the outer surface of the support particles at larger recirculation flow rates. Restricted diffusion of enzymes may be implicated in this phenomenon. These contacting effects may be significant considerations in the scaleup of processes for protein impregnation in porous supports, since apparent activity and stability of the final preparation depend on internal protein distribution.
Cholinesterase‐catalyzed resolution of D,L‐carnitine
Authors: Dropsy Eric P. , Klibanov Alexander M.
Published: December 2004

An enzymatic method for the preparative resolution of racemic carnitine (whose L‐isomer and its acyl‐derivatives have numerous therapeutical applications) has been developed. It is based on our finding that electriceel acetylcholinesterase hydrolyzes the D‐ but not the L‐isomer of acetylcarnitine. (Another cholinesterase tested, horse serum butyrylcholinesterase, is also stereospecific and hydrolyzes only the L‐isomer of butyrylcarnitine.) Acetylcholinesterase, covalently attached to alumina, was employed for the resolution of D,L‐carnitine; the latter was first chemically acetylated, then stereoselectively hydrolyzed with the immobilized enzyme, and finally the acetyl‐L‐carnitine and D‐carnitine produced were separated by ion‐exchange chromatography. Gram quantities of D,L‐carnitine were thereby resolved.
An operational strategy for unstable recombinant DNA cultures
Authors: Ryder D. F. , DiBiasio D.
Published: December 2004

A simple operational strategy is shown to offer a viable means of enhancing plasmid stability in chemostat systems where plasmid loss is a common problem. Feedback control can be used to stabilize coexistence states, which are naturally unstable in the system investigated, and thus gurantee retention of the plasmid‐carrying strain. The strategy exploits the normally undesirable characteristics of substrate inhibited growth kinetics, and is illustrated with specific reference to methanolutilizing organisms. Since the methodology may be easily implemented in practice, it offers an alternative to costly environmental methods such as antibiotic addition.
Influence of the presence of Zymomonas anaerobia on the conversion of cellobiose, glucose, and xylose to ethanol by Clostridium saccharolyticum
Authors: Asther M. , Khan A. W.
Published: December 2004

To convert sugar mixtures containing cellobiose, glucose, and xylose to ethanol in a single step, the possibility of using a coculture consisting of Clostridium saccharolyticum and Zymomonas anaerobia was studied. In monoculture, C. saccharolyticum utilized all three sugars; however, it preferentially utilized glucose and produced acetic acid in addition to ethanol. The formation of acetic acid from the metabolism of glucose inhibited the growth of C. saccharolyticum and, consequently, the utilization of cellobiose and xylose. In monoculture, Z. anaerobia utilized glucose at a rate of 50 g/L day, but it did not ferment cellobiose or xylose. In coculture, Z. anaerobia converted most of the glucose to ethanol during the lag phase of growth of C. saccharolyticum, which then converted cellobiose and xylose to ethanol. The use of this coculture increased both the rate and the efficiency of the conversion of these three sugars to ethanol, and produced relatively small amounts of acetic acid.
Effect of dilution on carboxymethylcellulase and xylanase assays
Authors: Cauchon Nicole , Leduy Anh
Published: December 2004

It has been demonstrated that the dilution of samples prior to the carboxymethylcellulase and xylanase assays causes serious discrepancies in the numerical values obtained for the enzyme activities. Even when the sample is assayed with the identical procedure, one could obtain different numerical values of the enzyme activity U depending on how much this sample has been diluted before the enzyme assay. Two crude commercial cellulase samples of Aspergillus niger and Trichoderma viride as well as the culture filtrate of our newly isolated acidophilic fungus have been used for the demonstration. An empirical method for reporting the cellulolytic activity by taking into account this dilution effect is proposed.
Continuous ethanol fermentation using immobilized yeast cells
Authors: Nagashima Minoru , Azuma Masaki , Noguchi Sadao , Inuzuka Keiichi , Samejima Hirotoshi
Published: December 2004

Growing cells of Saccharomyces cerevisiae immobilized in calcium alginate gel beads were employed in fluidizedbed reactors for continuous ethanol fermentation from cane molasses and other sugar sources. Some improvements were made in order to avoid microbial contamination and keep cell viability for stable long run operations. Notably, entrapment of sterol and unsaturated fatty acid into immobilized gel beads enhanced ethanol productivity more than 50 g ethanol/L gel h and prolonged life stability for more than one‐half year. Cell concentration in the carrier was estimated over 250 g dry cell/L gel. A pilot plant with a total column volume of 4 kL was constructed and has been operated since 1982. As a result, it was confirmed that 8–10%(v/v)ethanol‐containing broth was continuously produced from nonsterilized diluted cane molasses for over one‐half year. The productivity of ethanol was calculated as 0.6 kL ethanol/kL reactor volume day with a 95% conversion yield versus the maximum theoretical yield for the case of 8.5% (v/v) ethanol broth.
Economic evaluation of alternative ethanol fermentation processes
Authors: Maiorella B. L. , Blanch H. W. , Wilke C. R.
Published: December 2004

Eleven alternative fermentation schemes for ethanol production are compared. Conventional batch, continuous, cell recycle, and immobilized cell processes, as well as membrane, extraction, and vacuum processes which remove ethanol from the broth selectively as it is produced, are considered. The processes are compared on identical bases using a consistent model for the yeast metabolism. Both molasses and cellulose hydrolyzate are considered as feeds. Optimized ethanol plants, including feed preparation, fermentation, and product recovery sections are designed and total costs are projected.
Studies on cellulase production by a mutant—penicillium funiculosum uv‐49
Authors: Joglekar A. V. , Karanth N. G.
Published: December 2004

In search of hypercellulolytic microorganisms, ultraviolet irradiation carried out with Penicillium funiculosum has yielded a superior mutant. The investigations reported in this article are shake flask studies on some important nutritional requirements of the mutant, namely, nitrogen source, carbon source, and inducers. The mutant shows an ability to metabolize inorganic nitrogen sources like urea and sodium nitrate both for growth and enzyme production. A comparison of the long‐term saccharification ability and the utilization efficiency of the mutant enzyme with those reported in the literature is also carried out, showing the superior performance of the mutant enzyme.
Modification of wheat straw in a high‐shear mixer
Authors: Carr M. E. , Doane W. M.
Published: December 2004

Wheat straw (Ws)was treated in a pilot‐scale continuous mixer to disrupt the lignin–hemicellulose–cellulose (LHC) complex. An efficient and practical method was desired to remove lignin and hemicellulose (pentosans)rapidly and efficiently from the lignocellulose complex and to make the cellulose accessible to enzymatic hydrolysis. Milled WS in the presence of various chemicals in aqueous solutions was extruded from the mixer under several processing conditions. Chemicals used were sodium hydroxide (NaOH) sodium sulfide (Na2S), anthraquinone (AQ), anthrahydroquinone (AHQ), hexamethylenediamine (HMDA), hexamethylenetetramine (HMTA) hydrogen peroxide (H2O2), and ferrous ammonium sulfate (FAS), which were used alone and in selected combinations. Concomitantly, WS was treated in laboratory batches using similar reaction conditions, except for mixing and shearing. In extrusion treatments of WS at 20% concentration at 97°C for 5.5 min with NaOH (15.7%, dry WS basis), NaOH (15.7%) + AHQ (0.3%), and NaOH (12.7%) + Na2S (5.0%), 64–72% of the WS lignin and 36–43% of the pentosans were removed from aqueously washed extrudates (residues). This compares with 46–56% and 23–27%, respectively, for batch treatments. AHQ and Na2S enhanced delignification. Cellulase treatment of the residues, which contained about 99%of the WS cellulose, converted 90–92%of the cellulose to glucose compared with 61–69%for the batch pretreatments. Treatments of WS with amines and H2O2 (alone or combined with NaOH)were less effective for LHC disruption. In all instances the relatively high‐shear extrusion treatments were superior to the laboratory‐batch treatments.
Potential of mass algae production in Kuwait
Authors: Prokop Ales , Fekri Mansoor
Published: December 2004

The rationale for efficient light absorption by algae at a production unit is given and design details of an intensive thin‐layer technology outdoor (2.11 m2) unit are presented. Data on productivity under extreme conditions were collected. Maximum productivity data are close to those reported in the literature for similar geographic areas.
Ion exchange/complexation of the uranyl ion by Rhizopus biosorbent
Authors: Treen‐Sears Margaret E. , Volesky Bohumil , Neufeld Ronald J.
Published: December 2004

Nonliving biomass of nine Rhizopus species effectively sequestered the uranyl ion from solution, taking up 150–250 mg U/g dry cells at 300 ppm U equilibrium concentration in solution, and 100–160 mg U/g dry cells with 100 ppm U in solution. The affinity of this biosorbent for the uranyl ion was found to be affected by timing of harvesting and medium composition. Uptake of the uranyl ion by nonliving biomass of Rhizopus oligosporus was due to ion exchange or complexation, since binding was reversed by the addition of complexing ligands or the reduction of pH to a value less than 2. Uptake isotherms were interpreted in terms of a model of multiple equilibria. At pH ≤ 2, or in the presence of NO, Cl−, SO, or EDTA (ethylenediamine–tetra‐acetate), the quantity of UO that was bound was a constant fraction of that bound at pH 4 in the absence of ligands. This action indicated simple competition for uptake sites between H3O+ and UO for uptake sites, or for UO between the biomass and ligands in solution. If oxalate or thiocyanate was present, however, the complexed species were sequestered by the biomass. Biomass of Rhizopus arrhizus, which grew as pellets, was subsequently used in a packed sorption column where it exchanged hydrogen ions for uranyl ions (2 H+: 1 UO). Concentrated uranyl solutions were eluted in sulfuric or nitric acids, and the biomass was reused eight times with no apparent deterioration of the biosorbent.
Cellular reporoduction and extracellular polymer formation by Pseudomonas aeruginosa in continuous culture
Authors: Robinson Joseph A. , Trulear Michael G. , Characklis William G.
Published: December 2004

The kinetics of cellular reproduction and the rate and extent of synthesis of extracellular polymeric substances (EPS) were investigated for P. aeruginosa growing in glucose‐limited chemostats. μmax and Ks estimates of 0.4 h−1 and 2 mg glucose C/L, respectively, at 25°C were obtained for this bacterium. The extent of EPS formation was inversely related to the growth rate of P. aeruginosa. The rate of EPS formation had both growth‐ and non‐growth‐associated components. The growth‐associated polymer formation rate coefficient (k) was 0.3 mg polymer C/mg cellular C and the non‐growth‐associated polymer formation rate coefficient (k′) was 0.04 mg polymer C/mg cellular C/h. The values for k and k′ must be regarded as provisional since the product formation data were quite variable at low dilution rates. Estimates of the cellular (Yx/s) and polymer (Yp/s) yield coefficients were 0.3 mg cellular C/mg glucose C and 0.6 mg polymer C/mg glucose C, respectively. Most of the non‐growth‐associated consumption of glucose detected was due to exopolymer formation.
Estimation of yield, maintenance, and product formation kinetic parameters in anaerobic fermentations
Authors: Oner M. D. , Erickson L. E. , Yang S. S.
Published: December 2004

In many anaerobic fermentation processes, high energy bonds in adenosine triphosphate (ATP) are produced when available electrons are converted from organic substrate into extracellular organic products such as ethanol. The true growth yield and maintenance parameters are directly related to the product formation kinetic parameters for these anaerobic processes. Methods are presented which allow all of the experimental measurements to be used simultaneously to estimate these parameters. Results are presented for several different anaerobic fermentations.
Dried calcium alginate/magnetite spheres: A new support for chromatographic separations and enzyme immobilization
Authors: Burns Mark A. , Kvesitadze George I. , Graves David J.
Published: December 2004

Dried spheres made from an alginate solution containing magnetite particles have excellent potential as a support for enzyme immobilization and chromatographic applications. The beads were found to be much stronger than gels such as polyacrylamide and dextran, indicating that high flow rates and pressures could be used in column separations. The support withstood not only temperatures of up to 120°C, but also most pH values and common solvents. While some solutions, such as phosphate buffers, dissolved the spheres, stabilization with Tyzor TE® eliminated this problem. The physical properties of the beads include a glasslike density of 2.2 g/mL, excellent sphericity, low porosity, and a narrow size distribution. The magnetite present in the support allows the beads to be used for magnetic separations such as high gradient magnetic filtration. Their high degree of microroughness provides a large exposed surface area for enzyme and ligand binding. Mixed Actinomyces fradiae proteases and Aspergillus niger α‐amylase, two enzymes representative of classes which attack large substrates, were immobilized on the bead's surface with high activity and stability. A cyanuric dye which can be used in chromatographic applications (Cibacron Blue F3GA®) was also readily coupled to the surface of this support with good yield. The support should have a wide range of applications in bioseparation and immobilized biochemical technology.
Design of a system for the control of low dissolved oxygen concentrations: Critical oxygen concentrations for Azotobacter vinelandii and Escherichia coli
Authors: Chen J. , Tannahill A. L. , Shuler M. L.
Published: December 2004

The physiological activity of microorganisms in environments with low dissolved oxygen concentrations often differs from the metabolic activity of the same cells growing under fully aerobic or anaerobic conditions. This article describes a laboratory‐scale system for the control of dissolved oxygen at low levels while maintaining other parameters, such as agitator speed, gas flowrate, position of sparger outlet, and temperature at fixed values. Thus, it is possible to attribute in dilute nonviscous fermentations all physiologic changes solely to changes in dissolved oxygen. Experiments were conducted with Azotobacter vinelandii and Escherichia coli. Critical oxygen concentrations for growth (that value of oxygen allowing growth at 97% of μmax) were measured as 0.35 ± 0.03 mg/L for A. vinelandii and 0.12 ± 0.03 mg/L for E. coli. These values are significantly different from the commonly quoted values for critical oxygen concentrations based on respiration rates. Because of the superior dissolved oxygen control system and an improved experimental protocol preventing CO2 limitation, we believe that the values reported in this work more closely represent reality.
Measurements of lactate concentration using lactate oxidase and an electrochemical oxygen sensor
Authors: Makovos E. B. , Liu C. C.
Published: December 2004

Lactate oxidase was used in combination with an electrochemical dissolved oxygen sensor to measureL‐lactate concentration in the physiological saline solution. The rate of oxygen consumption was found to have an excellent linear relationship with the lactate concentration on a log‐log scale in the lactate concentration range of 0.3–25 mM. This detection does not require additional reagents and can be developed into a simple method ofL‐lactate determination. The effects of the temperature and pH of the solution on the reaction rate were investigated and discussed.
Analysis of a diffusion‐limited hollow fiber reactor for the measurement of effective substrate diffusivities
Authors: Davis Mark E. , Watson Layne T.
Published: December 2004

Mathematical analyses of a diffusion‐limited hollow fiber reactor for the measurement of effective substrate diffusivities are presented. An analytical solution to the mathematical model with a first order substrate consumption rate is used to show that the procedure of Webster and Shuler1 is incorrect. A rigorous analysis that requires numerical solution is also outlined for any form of the substrate consumption rate. These analyses allow for more accurate estimations of effective substrate diffusivities since they should be used in conjunction with integral reactor behavior.
Automatic supplementation of minerals in fed‐batch culture to high cell mass concentration
Authors: Suzuki Takahiro , Mori Hironori , Yamané Tsuneo , Shimizu Shoichi
Published: December 2004

Automatic constant‐value control of mineral ions was attempted in semibatch culture of high cell mass concentration (more than 150 g dry cell/L) with ethanol and ammonia feeds. Equations were derived from the mass balance principle to calculate the required concentration of each mineral ion in the mineral feed solution, taking into account both the decrease in the volume of the culture supernatant as a proportion of the whole culture broth and the increase in the volume of the whole culture broth during the cultivation. The mineral solution was supplied automatically, linked either with ethanol feed or ammonia water feed. The actual concentrations of mineral ions could be kept within small variations. To adjust the supplementation in accordance with the culture change from oxygen sufficiency (early growth phase) to oxygen deficiency (later growth phase), the concentration of each mineral ion was altered stepwise when the dissolved oxygen concentration fell to zero. The mineral supplementation gave better results coupled with ethanol feed than with ammonia feed. The mineral ions studied were K+, Mg2+, Na+, Fe2+, Zn2+, Ca2+, Co2+, Cu2+, Mn2+, NH+4, PO and SO.
Characteristics of carbohydrate degradation and the rate‐limiting step in anaerobic digestion
Authors: Noike Tatsuya , Endo Ginro , Chang Juu‐En , Yaguchi Jun‐Ichi , Matsumoto Jun‐Ichiro
Published: December 2004

The characteristics of the degradation of cellulose, soluble starch, and glucose in the acidogenic phase and the effects of the substrate loading rate and biological solids retention time on the methanogenic phase of anaerobic digestion were investigated. The results obtained from continuous experiments using laboratory‐scale anaerobic chemostat reactors elucidated the true rate‐limiting step of anaerobic digestion. The specific rate of substrate utilization decreased in the following order: glucose, soluble starch, acetic acid, and cellulose. The rate of the hydrolysis of cellulose was so low that this was shown to be the rate‐limiting step in overall anaerobic digestion. Among methanogenic bacteria Methanosarcina would provide a higher substrate utilization rate than Methanothrix, and the maximum allowable substrate loading rate in the methanogenic phase was 11.2 g acetic acid/L day.