bluuebunny/crossref_metadata_2025 huggingface dataset:
Aerobic and anaerobic microbial treatment alternatives for shellfish processing wastewaters in continuous culture
Authors: Pohland Frederick G. , Hudson James W.
Published: December 2004

Shellfish processing wastewaters were characterized and subjected to laboratory‐scale treatability investigations using continuous flow chemostats operated under both aerobic and anaerobic conditions with and without biological solids recycle. System operation and evaluation employed hydraulic retention time as the controlled variable with substrate removal and biomass production as dependent variables. Additional variables specific to anaerobic operation included total and methane gas production rate and volatile acids generation. Application of a kinetic model incorporating the Monod substrate concentration– growth rate function allowed estimation of kinetic coefficients μmax, kd, Y, and Ks.

Aerobic treatment of the wastewaters could be adequately described by the kinetic model presented. However, total efficiencies were notably affected by the inherent morphological differences induced by changing hydraulic flows as reflected by poor solids separation at lower and higher retention times. Anaerobic treatment, although not amenable to kinetic description by the model and data presented, exhibited a limited potential for wastewater stabilization in that soluble substrate removals and methane production occurred at all retention times. Difficulties in successfully describing the system kinetically stemmed from an inability to quantify influent solids liquifaction rates. Moreover, evidence of some substrate associated inhibition of methanogenesis was apparent. Solids recycle tended to reduce the inhibitory influences and to increase treatment efficiencies in both the aerobic and anaerobic processes.
The use of α‐galactosidase and invertase in hollow fiber reactors
Authors: Korus Roger A. , Olson Alfred C.
Published: December 2004

Invertase and α‐galactosidase have been immobilized in hollow fiber cartridges with no detectable enzyme leakage and used for the hydrolysis of sucrose and raffinose, respectively. For both hollow fiber immobilizes enzymes nearly complete substrate conversion is possible. Enzyme stabilities in polysulfone hollow fibers which have been preconditioned with bovine albumin approach the stabilities of the free enzymes.
Chemically activated collagen for amyloglucosidase attachment. Use in a helicoidal reactor
Authors: Brillouet Jean‐Marc , Coulet Pierre R. , Gautheron Daniele C.
Published: December 2004

Amyloglucosidase was covalently bound to collagen sheets by a previously described method. The time of acidic methylation (first step of the collagen activation process) was important to obtain a good enzymatic surfacic activity. Homogeneity of the coupling procedure on the surface of collagen films was shown. Some properties of free enzyme were not affected after grafting: optimum pH and temperature, activation energy, and Km for maltose. Heat stability of the bound enzyme was slightly better; Km for soluble starch increased fivefold. In contrast, the maximal velocity in the presence of soluble starch remained four times that of maltose hydrolysis.

Amyloglucosidase collagen membranes were used in a helicoidal reactor to produce glucose from maltose or soluble starch solutions. Tracer studies have shown that the helicoidal reactor behaved as a CSTR. The influence of maltose concentration and flow rate on conversion was studied and confirmed the absence of diffusional limitations for maltose. Recycling of concentrated solutions of maltose and soluble starch indicated strong diffusional restrictions for soluble starch. The catalytic support kept all its activity for 18 days continuous operation at 40°C and 80% after 17 months storage at 4°C.
Characteristics of yeast invertase immobilized on porous cellulose beads
Authors: Dickensheets Paul A. , Chen Li Fu , Tsao George T.
Published: December 2004

Invertase from Candida utilis was immobilized on porous cellulose beads by an ionic‐quanidino bond. The immobilized invertase showed optimum activity between pH 4.0 and 5.4, while the free enzyme had a sharp optimum at pH 4.1. Both temperature profiles were fairly similar up to 55°C. However, above this temperature the immobilized enzyme was more stable than the free enzyme. From the temperature data, the activation energies were found to be 7,322 and 4,052 cal/g mol for the free and the immobilized enzyme, respectively.

Candida invertase shows characteristics of substrate inhibition. Both the Km and Ki for the free and the immobilized enzymes were determined. The apparent Ki for the immobilized invertase was much higher than the Ki of the free enzyme, suggesting a diffusion effect. Immobilized invertase molecules deep in the pores only see sucrose concentrations much less than the bulk concentrations. Immobilization, thus, offers certain processing advantages in this regard.
Fermentation of glucose by Acetobacter melanogenus
Authors: Stroshane R. M. , Perlman D.
Published: December 2004

Growing cultures of Acetobacter melanogenus ATCC 9937 converted D‐glucose to 2,5‐diketo‐D‐gluconic acid with D‐gluconic acid and 5‐keto‐D‐glucose acid as intermediates. The 2,5‐diketo‐D‐gluconic acid was isolated from the fermented medium by treatment with an anion exchange resin.
Kinetcs and decay of fumarase activity of immobilized Brevibacterium ammoniagenes cells for continuous production of L‐malic acid
Authors: Yamamoto Kozo , Tosa Tetsuya , Yamashita Kiyokazu , Chibata Ichiro
Published: December 2004

The kinetics of the reversible fumarase reaction of immobilized Brevibacterium ammoniagenes cells and the decay behavior of enzyme activity were investigated in a plug flow system. The time course of the reaction in the immobilized cell column was well explained by the time‐conversion equation including the apparent kinetic constants of the immobilized cell enzyme. The decay rate of fumarase activity was faster in the upper sections of the column (inlet side of the substrate solution) compared with the lower sections when 1M sodium fumarate (pH 7.0) was continuously passed through the column at 37°C. It was shown that the decay rate of the fumarase activity in the immobilized cell column depends on the flow rate of the substrate solution. The effect of flow rate on the decay rate of enzyme activity was considered to be related to the rate of contamination of enzyme with poisonous substances derived from the substrate solution or to the rate of leakage of enzyme stabilizers and/or enzyme itself from the immobilized cells.
Comparison of the economics of acid and enzymatic hydrolysis of newsprint
Authors: Grethlein Hans E.
Published: December 2004

In order to compare the process economics of making glucose from cellulose, a plant design is presented using acid hydrolysis which can be compared with a published design using enzyme hydrolysis. A common design basis is used; namely, an input capacity of 885 ton/day newsprint with a common technique of cost estimation. The cost of making glucose is in the range of 1.75 to 2.45 cents/lb, depending on the slurry concentration fed to the reactor for the acid hydrolysis. This cost range is less than the published estimate of 5.2 cents/lb for enzymatic hydrolysis.
An enzyme electrode for measurement of penicillin in fermentation broth: A step toward the application of enzyme electrodes in fermentation control
Authors: Nilsson Hans , Mosbach Klaus , Enfors Sven‐Olof , Molin Nils
Published: December 2004

A penicillin sensitive enzyme electrode has been used to analyze the concentration of benzylpenicillin in fermentation broth. The electrode response time was in the region of 2 min and the response to penicillin concentration was linear within the range of 1 to 10mM. The buffering capacity of the medium influenced the sensitivity of the electrode. At low buffer capacity the sensitivity of the enzyme electrode to penicillin was very high, but then the sensitivity to small changes in buffer capacity was relatively large. At high buffer capacity the sensitivity to penicillin was reduced and the electrode became less dependent on changes to buffer capacity. Constant calibration curves were repeatedly obtained with the electrode when used for 2 hr daily in a fermentation medium over a six day period. Three methods devised to calibrate the electrode for use in fermentation media were investigated. Methods one and two, based on the relationship between electrode sensitivity and buffer capacity in phosphate buffer and in sterile media, gave rather high penicillin concentration values. The third method based on an internal standard was the most satisfactory.
Large scale preparation of purified exocellular DD‐carboxypeptidase–transpeptidase of Streptomyces strain R61
Authors: Fossati P. , Saint‐Ghislain M. , Sicard P. J. , Frère M. , Dusart J. , Klein D. , Ghuysen J. M.
Published: December 2004

The exocellular DD‐carboxypeptidase–transpeptidase that Streptomyces R61 excretes during growth has been produced in large fermentation units of 15 m3 total capacity. The yield from 15,000 liter culture filtrate was 1.080 g purified enzyme (92% purity) with a total recovery of 29% and at least a 2000‐fold increased specific activity.
Optimum operating mode for a class of fermentation
Authors: Ohno Hiromu , Nakanishi Eiji , Takamatsu Takeichiro
Published: December 2004

This paper is concerned with optimization of the operating mode of a fermentor. Combining the various modes of operation—batch, semibatch, and continuous—the operating pattern which maximizes the desired metabolic product in a single fermentor is determined by using Kelley's transformation method with Pontryagin's maximum principle. Kelley's transformation method is a device which avoids the singular situation which occurs when the usual procedure of selecting the optimal control function by the maximum principle breaks down. This is the case in the problem considered in this paper. For lysine fermentation, the best operating mode depends on the fermentor capacity and operating time. The results of this study are summarized thus: (i) when the operating time is “long enough,” optimal conditions require that continuous operation follows either semibatch and/or batch operation, and (ii) when the fermentor capacity becomes “large enough,” semibatch operation becomes important.
The rotorfermentor. I. Description of the apparatus, power requirements, and mass transfer characteristics
Authors: Margaritis Argyrios , Wilke Charles R.
Published: December 2004

A novel fermentation device, the rotorfermentor, is described and some experimental results are presented on power requirements and oxygen mass transfer characteristics of the rotorfermentor. This fermentation device is designed to achieve high cell concentrations in batch and continuous cultures. Basically, the rotorfermentor consists of a rotating microporous membrane which is enclosed within a stationary fermentor vessel. The metabolic products in the broth are continuously removed by filtration through the rotating microporous membrane while the growing cells can be retained inside the fermentor. This dual function of cell growth and concentration with the simultaneous removal of metabolic products is the essential characteristic of the rotorfermentor.
Effect of immobilized enzyme deactivation in fixed‐ and fluid‐bed reactors
Authors: Sadana Ajit
Published: December 2004

A two‐parameter theoretical model is developed to evaluate the effect of immobilized enzyme deactivation on substrate conversion in fixed‐ and fluid‐bed reactors under diffusion‐free conditions. The method describes a simple reaction in which three different immobilized enzyme deactivation forms are considered, and an expression is developed to evaluate the effect of immobilized enzyme deactivation on yield in a consecutive reaction. Comparison of reactor performances for the two reactor types reduces to a comparison of the appropriate dimensionless parameters. The practical implications of the development are illustrated through an example.
Error in oxygen measurements in open systems owing to oxygen consumption in unstirred layer
Authors: Lundsgaard J. S. , Grønlund J. , Degn H.
Published: December 2004

When a steady‐state oxygen concentration is measured with a membrane‐covered probe in an open system, the oxygen consumption in the unstirred layer gives rise to an error of measurement whose seriousness depends on the kinetics of the oxygen‐consuming process. First‐order oxygen consumption in the sample causes a proportional reduction in the signal so that the calibration in curve remains linear. A zeroth‐order process causes the calibration curve to be offset from the origin, but it remains linear. Oxygen consumption according to the Michaelis–Menten equation causes the calibration curve to become nonlinear with the maximum deviation at the lower end of the scale. The error determines a lower limit for usefulness of membrane‐covered probes. Steady‐state kinetics at oxygen concentrations in the order of KM cannot be determined with a membrane‐covered probe for enzyes with KM for oxygen lower than 0.01μM. In a dense culture of respiring microorganisms, no oxygen will reach the probe when the bulk concentration of oxygen is in the order of KM.
Bacterial growth on organic polymers
Authors: Maxham John V. , Maier Walter J.
Published: December 2004

Mathematical models are developed describing unsteady‐state bacterial growth on organic polymers that are hydrolyzed by extracellular enzymes secreted by the bacteria to yield low‐molecular‐weight oligomers that may be directly transported across bacterial cytoplasmic membranes and hence metabolized. Two different modes of extracellular enzyme action on the organic polymer are considered. In one case, the enzyme is exoacting yielding a transportable oligomer with each polymer bond hydrolyzed. In the other case, the enzyme is endoacting yielding a series of oligomers upon random cleavage of the polymer bonds with oligomers up to a certain chain length assumed to be transportable. These models are exploited to show under what circumstances the rate of hydrolysis by the extracellular enzyme to yield transportable oligomers influences the bacterial growth rate. It is shown that an initial lag period, an accentuated declining growth phase, and a low overall rate of bacterial growth will be some of the manifestations when the rate of hydrolysis has a strong influence.
Continuous fermentation to produce fungal protein. Effect of growth rate on the biomass yield and chemical composition of Fusarium moniliforme
Authors: Macris B. J. , Kokke R.
Published: December 2004

Fusarium moniliforme was grown on a carob aqueous extract in a chemostat for fungal protein production. The substrate was adjusted to provide 0.5% carob sugars supplemented with inorganic salts. The dilution rate varied from 0.086 to 0.227 hr−1 under constant conditions of temperature (30°C), pH (4.5), and oxygen saturation (60–80%). A yield of 0.709 g dry mycelium/g consumed carob sugar and a productivity value of 0.687 g dry mycelium/liter hr−1 were obtained at μ = 0.205 hr−1. The maintenance coefficient was 0.077 g carob sugar/g dry mycelium hr−1. While the carbohydrate and purine content of dry mycelium increased at μ values from 0.114 to 0.205 hr−1 both true (Lowry) and crude (N × 6.25) protein contents decreased at the same μ range. Maximum values of 36.3% true and 47.9% crude protein of dry mycelium were obtained at μ = 0.114 hr−1, whereas a minimum purine content of 99.8 μmol/g corresponding to 6.42% nucleic acids was recorded at μ = 0.086 hr−1. It was concluded that a continuous fermentation of carob aqueous extract using F. moniliforme should be operated at growth rates of approximately 0.205 hr−1 in order to maximize protein production.
Kinetics of collagen‐bound sorbitol dehydrogenase in the rotating membrane reactor: Opposite variations of affinity constants under diffusional limitations
Authors: Paul François , Coulet Pierre R. , Gautheron Danièle C. , Engasser Jean‐Marc
Published: December 2004

Sorbitol dehydrogenase was bound to the surface of acyl‐azide‐activated collagen membranes and its kinetics was investigated as a model of two‐substrate or cofactor‐requiring enzyme reactions. The study was performed with the “rotating membrane reactor” especially designed to obtain a precise variation of the external mass‐transfer coefficient, and thus the direct visualization of diffusional effects on the bound enzyme behavior. Diffusional limitations for NADH were found to decrease the apparent affinity for NADH, but to increase the apparent affinity for fructose. Such opposite effects of diffusional limitations on apparent affinities are generally applicable to reactions involving two substrates or a substrate and a cofactor of widely different affinities.
Technical aspects of separation using aqueous two‐phase systems in enzyme isolation processes
Authors: Kroner K. H. , Hustedt H. , Granda S. , Kula M.‐R.
Published: December 2004

Technical aspects of the separation of aqueous two‐phase systems in a commercial separator were studied in detail. For the Gyrotester B, the smallest available separator, a flow rate of 200 ml/min and a length of the regulating screw in the outlet port of 13.5 mm were found as optimal operation parameters for the separation of a poly(ethylene glycol) (PEG)/dextran two‐phase system. In the presence of cells and cell debris the characteristics of the carrier two‐phase systems are changed, most notably the phase ratio. Nevertheless good separation and high throughput can be maintained up to 30% wet cell material in the complete system. Using this method the enzyme pullulanase was extracted from 6.65 kg Klebsiella pneumoniae in 88% yield in a single step in less than 2 hr. A yield of 90% was predicted for this step based upon laboratory data, indicating that the performance of the extraction and separation can be calculated with the necessary accuracy and the further scale‐up of the process should be accomplished quite easily. The hydrophilic polymers Constituting the phase system will often stabilize the enzymes, So that the separation can be carried out at room temperature without extensive cooling. The method of enzyme solubilization or cell disruption is not decisive for the successful extraction of the enzymes, the only limitation being the necessity to find a suitable two‐phase system where the desired product and the cells or cell debris will partition in opposite phases. This is shown for α‐glucosidase from Saccharomyces carlsbergensis and three aminoacyl‐tRNA‐synthetases from Escherichia coli. The results obtained demonstrate that aqueous two‐phase systems can be separated in commercially available separators with high capacity and efficiency. It can be expected that the advanced separation technology available from chemical engineering studies can also be used for the development of large‐scale isolation processes for enzymes involving liquid–liquid partitions.
Immobilized glucose oxidase–catalase and their deactivation in a differential‐bed loop reactor
Authors: Prenosil J. E.
Published: December 2004

Glucose oxidase containing catalase was immobilized with a copolymer of phenylenediamine and glutaraldehyde on pumice and titania carrier to study the enzymatic oxidation of glucose in a differential‐bed loop reactor. The reaction rate was found to be first order with respect to the concentration of limiting oxygen substrate, suggesting a strong external mass‐transfer resistance for all the flow rates used. The partial pressure of oxygen was varied from 21.3 up to 202.6 kPa. The use of a differential‐bed loop reactor for the determination of the active enzyme concentration in the catalyst with negligible internal pore diffusion resistance is shown. Catalyst deactivation was studied, especially with respect to the presence of catalase. It is believed that the hydrogen peroxide formed in the oxidation reaction deactivates catalase first; if an excess of catalase is present, the deactivation of glucose oxidase remains small. The mathematical model subsequently developed adequately describes the experimental results.
Computer control of bakers' yeast production
Authors: Wang Henry Y. , Cooney Charles L. , Wang Daniel I. C.
Published: December 2004

The Biotechnology and Bioengineering study presented here was undertaken to demonstrate the usefulness of computer control for the production of yeast from molasses. A flexible control system was developed by using an on‐line computer for the monitoring of cell mass and employing anticipatory control to maintain the maximum productivity. Process disturbances were minimized by employing a multivariable feedback control system to prevent ethanol formation. The control strategy acted to keep overall conversion yield at its maximum level, about 0.5 g cell/ g sugar, while maintaining high volumetric productivity between 3 and 5 g/liter‐hr. Results are presented to show the effectiveness of simultaneous anticipatory and feedback contol in overcoming problems of oxygen starvation, molasses quality, and variable inoculum size.
Process analysis and optimal design of a fermentation process based upon elemental balance equations: Generalized semitheoretical equations for estimating rates of oxygen demand and heat evolution
Authors: Ho Lewis
Published: December 2004

Based upon elemental balance equations, generalized semitheoretical equations are developed for estimating the rates of oxygen demand and heat evolution of a fermentation process. The results estimated by these equations are in good agreement with data obtained from yeast–hydrocarbon and yeast–carbohydrate fermentation processes for citric acid production. Furthermore, a direct relationship between rates of oxygen demand and heat evolution is derived with a correlation constant of 0.18 kcal/mM O2.The relationship has been verified by data of citric acid fermentation processes and also confirmed by published data. These derived equations would be useful for process design and optimization.
Activated‐sludge process dynamics with continuous total organic carbon and oxygen uptake measurements
Authors: Mona R. , Dunn I. J. , Bourne J. R.
Published: December 2004

The dynamic responses of a bench‐scale activated‐sludge process to step changes and square‐wave inputs in the feed flow and concentration were measured. Instrumentation permitted the continuous measurement of the oxygen uptake rate and dissolved organic carbon responses. Notable were the sensitivity of the oxygen uptake rate to process changes and the reliability of the dynamic oxygen electrode method. The responses were found to be greatly influenced by the organic loading, FS0/XV, which was incorporated into a load‐dependent kinetics model. Simulations showd good agreement with experiment in the case of the square‐wave disturbances. Because of the changing and complex nature of the activated sludge it was necessary to reestimate the parameter set for each run.
Studies on quantitative physiology of Trichoderma reesei with two‐stage continuous culture for cellulose production
Authors: Ryu Dewey , Andereotti R. , Mandels M. , Gallo B. , Reese E. T.
Published: December 2004

By employing a two‐stage continuous‐culture system, some of the more important physiological parameters involved in cellulose biosynthesis have been evaluated with an ultimate objective of designing an optimally controlled cellulose process. The two‐stage continuous‐culture system was run for a period of 1350 hr with Trichoderma reesei strain MCG‐77. The temperature and pH were controlled at 32°C and pH 4.5 for the first stage (growth) and 28°C and pH 3.5 for the second stage (enzyme production). Lactose was the only carbon source for the both stages. The ratio of specific uptake rate of carbon to that of nitrogen, Q(C)/Q(N), that supported good cell growth ranged from 11 to 15, and the ratio for maximum specific enzyme productivity ranged from 5 to 13. The maintenance coefficients determined for oxygen, MO, and for carbon source, MC, are 0.85 mmol O2/g biomass/hr and 0.14 mmol hexose/g biomass/hr, respectively. The yield constants determined are: YX/O = 32.3 g biomass/mol O2, YX/C = 1.1 g biomass/g C or YX/C = 0.44 g biomass/g hexose, YX/N = 12.5 g biomass/g nitrogen for the cell growth stage, and YX/N = 16.6 g biomass/g nitrogen for the enzyme production stage. Enzyme was produced only in the second stage. Volumetric and specific enzyme productivities obtained were 90 IU/liter/hr and 8 IU/g biomass/hr, respectively. The maximum specific enzyme productivity observed was 14.8 IU/g biomass/hr. The optimal dilution rate in the second stage that corresponded to the maximum enzyme productivity was 0.026 ∼ 0.028 hr−1, and the specific growth rate in the second stage that supported maximum specific enzyme productivity was equal to or slightly less than zero.
Alternate method of calculating the free‐energy change accompanying the growth of Saccharomyces cervisiae (Hansen) on three substrates
Authors: Battley E. H.
Published: December 2004

A methods is described for determining the free energy of formation of the cells of Saccharomyces cerevisiae (Hansen) that are formed as the result of anaerobic growth on glucose, and aerobic growth on glucose and enthanol. The method is based on the direct relationship that exists between the enthalpy changes and the free‐energy changes that accompany the oxidation of 1g cellular material formed during these growth reactions and the degree of reduction of the same material. When the results of these calculations are used together with the free energies of formation of the reactions and of other products of a given growth reaction, it becomes possible to calculate the free‐ energy change accompanying this reaction. These free‐energy changes are in excellent agreement with those calculated by another methods based on the hypothesis that free‐energy change accompanying the conversion of the substrate plus other reactions into cellular material plus other products is equal to Zero.
Continuous deacetylation of cephalosporins
Authors: Konecny Jan , Sieber M.
Published: December 2004

Continuous deacetylation of cephalosporin C, 7‐aminocephalosporanic acid, and of 2‐methoxyethyl acetate in packed beds of an immobilized esterase is described by simple empirical equations relating conversion to space velocity and temperature. The choice of process conditions is discussed in relation to the effects of temperature on column efficiency, column life, growth of microbial contaminants, and the rates of thermal decomposition of the substrates. At the preferred temperature of 10°C columns were operated continuously for one month with only small losses in efficiency.
Interspecific interactions in a methane‐utilizing mixed culture
Authors: Lamb S. C. , Garver J. C.
Published: December 2004

A two‐member methane‐utilizing mixed culture of bacteria, formed by combining two pure cultures isolated from a naturally occurring methane‐utilizing mixed culture, was studied in continuous culture. From the nutritional requirements and substrate ranges of the pure cultures, a mechanism for the interspecific interactions occurring in the mixed culture was proposed. Product formation kinetics were determined in continuous culture for each product involved in the proposed mechanism. From this proposed mechanism a mathematical model was derived based on simple material balance equations around a single‐stage chemostat. The steady‐state predictions of this model were compared to experimental results obtained from continuous‐culture experiments with the two‐member methane‐utilizing mixed culture. Interspecific interactions occurring in two‐member methanol‐utilizing and three‐member methane‐utilizing mixed cultures have also been discussed.
Kinetic study of a hollow‐fiber enzyme reactor
Authors: Kitano Hiromi , Yoshijima Shigemi , Ise Norio
Published: December 2004

Enzymes, such as urease and uricase, were entrapped in three kinds of hollow fibers. The apparent Michaelis–Menten constants Km(app) obtained for these enzyme reactors were always larger than Km of free enzyme because of the permeation resistance of substrate across the hollow‐fiber membrane. Km(app) increased with increasing degree of permeation resistance across the membrane by the increase in enzyme concentration. The half‐life of the entrapped urease in the continuous reaction system was 60–80% of that of free enzyme. Activation energies of hollow‐fiber enzyme reactors were always smaller than that of the free enzyme, because the activation energy of permeation was smaller than that of the enzyme reaction.
Regulatory aspects of bakers' yeast metabolism in aerobic fed‐batch cultures
Authors: Woehrer W. , Roehr M.
Published: December 2004

A highly instrumented computer‐coupled bioreactor is used to investigate metabolic changes of Saccharomyces cerevisiae in aerobic fed‐batch systems which are generally applied in bankers' yeast manufacture. The four types of metabolism (oxidation of glucose, aerobic fermentation, oxidation of glucose and ethanol, and oxidation of ethanol) appearing in such systems are characterized by four significant fermentation parameters: Respiratory quotient (RQ), glucose uptake rate (Qg), ethanol turnover rate (QEtOH), and growth yield on glucose (Yg). Below the critical glucose concentration glucose and ethanol are utilized simultaneously. The shift from aerobic fermentation to nondiauxic growth on glucose and ethanol is not only dependent on glucose concentration. but also on the precultivation on cells. The uptake of ethanol is controlled by the glucose supply except in the case when ethanol is limiting; the oxygen uptake rate (Qo2), however, is unaffected by the ratio of Qg and QEtOH. Critical glucose concentration is not a constant value for a particular strain, but varies corresponding to the nutritional state of the cells.
Stability of immobilized α‐chymotrypsin
Authors: Kawamura Yasuko , Nakanishi Kazuhiro , Matsuno Ryuichi , Kamikubo Tadashi
Published: December 2004

The thermal of free and immobilized α‐chymotrypsin was investigated experimentally and theoretically. The inactivation process of free α‐chymotrypsin was analyzed with a kinetic model which included a first‐ order reaction process and autolysis. The effects of ionic strength, Ca2+ concentration, and temperature are discussed here in terms of the estimated kinetic parameters included in this model. The inactivation process of α‐chymotrypsin immobilized onto various supports by several methods was investigated. The Contribution of thermal denaturation and autolysis to the inactivation depended upon the method of immobilization. To interpret quantitatively the non‐first‐order thermal denaturation process of the immobilized enzyme, a model in which the heterogeneity of the immobilized enzyme was taken into account is proposed.
Maximum production in a bakers' yeast fed‐batch culture by a tubing method
Authors: Dairaku Kazuo , Yamasaki Yoshihiko , Kuki Kazuo , Shioya Suteaki , Takamatsu Takeichiro
Published: December 2004

A feedback control system of the glucose feed rate in a bakers' yeast fed‐batch culture was developed by keeping the ethanol concentration constant. A PID controller and on–off controller were applied and discussed with the aid of the porous Teflon tubing method. Experimental results showed the effectiveness of the control system for avoiding the glucose effect and glucose starvation. It was shown that the feedback control system developed hare could achieve a maximum specific growth rate of 0.3 h−1 or a maximum cell yield of 0.5 g cell/g glucose in the fedhyphen;batch culture.
Immobilization of amyloglucosidase on alkylamine derivatives of metal‐link‐activated inorganic supports
Authors: Cabral J. M. S. , Novais J. M. , Cardoso J. P.
Published: December 2004

A new process to couple amyloglucosidase (AG) to inorganic supports is described. The technique consists in activating the support with a transition metal salt according to the metal‐link method and subsequent amination and linkage of the alkylamine derivative using glutaraldehyde. The various parameters susceptible of influencing the properties of the immobilized enzyme (IME) preparation are investigated. The best result are obtained when 100 mg of 1000‐Å controlled porous glass (CPG) are treated with 45 mg of TiCl4 and the activated carrier aminated using a 10‐g/L solution of hexamethylenediamine (HMDA) in carbon tetrachloride (10 Ml/100 mg). Preparation obtained according to the process here described show operational stabilities much superior to those of AG immobilized on the same support by the traditional metal‐link method or its variations. The mechanism involved in the preparation of the amino derivative of CPG is proposed.
Pollution control of swine manure and straw by conversion to Chaetomium cellulolyticum SCP feed
Authors: Moo‐Young M. , Chahal D. S. , Stickney B.
Published: December 2004

Swine manure has a very high pollution potential and obnoxious odor. Large farms particularly are confronted with a manure disposal problem since environmentally acceptable solutions are now required by government regulations. Swine manure was found to be a good source of supplementary nutrients to ferment wheat straw into single‐cell protein (SCP) with Chaetomium cellulolyticum when 0.13g (NH4)2SO4/g solid was used as an additional source of N. In batch fermentations, inhibitory effects, possibly due to soluble released from the straw during alkali or acid pretreatment, were overcome by starting the fermentation at about pH 7.0 and then reducing it to 5.0 during growth. An overall protein productivity of up to 66 mg/L h was obtained from a slurry mixture of 1% w/v solids of manure and straw. This compares favorably with 99 mg/L h when manure was fermented with glucose instead of straw as the main carbon source. A high protein productivity of 200 mg/L h was obtained from a slurry mixture containing anaerobically prefermented swine manure liquor and 1.5% w/v solids from straw. The final products of the manure and straw fermentations contained 25–30% DW crude protein and 6–20% DW cellulose and the materials were free of the original obnoxious odor and undesirable microbial contamination.
Application of porous teflon tubing method to automatic fed‐batch culture of microorganisms II. Automatic constant‐value control of fed substrate (ethanol) concentration in semibatch culture of yeast
Authors: Yamané Tsuneo , Matsuda Morio , Sada Eizo
Published: December 2004

An automatic feedback control system incorporating a porous Teflon tubing sensor was developed and a strain of yeast was cultivated semibatchwise in mineral salt medium by feeding pure ethanol as the sole carbon source. In the control system, The ethanol concentration was continuously measured by the porous Teflon tubing sensor combined with a flame ionization detector, and its output signals were furnished to an automatic feed controller which controlled an ethanol feed pump so that deviations from the set level of ethanol concentration might be corrected. The controller was constructed on the basis of proportional‐differential negative feedback control of which the proportional sensitivity and differentiation constants were estimated from the dynamic mass balance of ethanol. Precise measurement of temperature and compensation of the detector output signals for temperature fluctuations of culture broth were necessary to achieve good control. Cultivation experiments were carried out with three levels of concentrations: 102, 103, and 104 ppm. The relative deviations of the concentrations were less than ±0.5% for the 103‐ and 104‐ ppm levels but a little offset arose for the 102‐ppm levels. The growth of cells was at first exponential and then almost linear when the dissolved oxygen concentration dropped considerably.
Optimal design of airlift fermenters
Authors: Moresi Mauro
Published: December 2004

In this article a modeling of a draft‐tube airlift fermentor (ALF) based on perfect backmixing of liquid and plugflow for gas bubbles has been carried out to optimize the design and operation of fermentation units at different working capacities. With reference to a whey fermentation by yeasts the economic optimization has led to a slim ALF with an aspect ration of about 15. As far as power expended per unit of oxygen transfer is concerned, the responses of the model are highly influenced by kLa However, a safer use of the model has been suggested in order to assess the feasibility of the fermentation process under study.
A new sensor, the “filtration probe,” for quantitative characterization of the penicillin fermentation. I. Mycelial morphology and culture activity
Authors: Nestaas Eirik , Wang Daniel I. C.
Published: December 2004

In this article the filtration resistance of fungal (Penicillium) mycelia is shown to be quantitatively related to the morphology of the cells. On this basis, it was possible to determine the intracellular volume by simple filtration measurements. Since the dry weight of the cells can also be measured, a morphological variable‐the “hyphae density” (dry weight hyphae/volume hyphae)‐can be quantified. This variable typically is measured to have values in the range of 0.35–0.20 g/cm3; the lower values represent the final stages of the fermentation. It can be shown that this loss of cell material during fermentation is limited to cytoplasmic components, and that most (70%) of the components which disappear are proteins. Concurrent with and linearly related to this loss of proteins, the culture activity in terms of both cell maintenance energy (respiration activity) and penicillin synthesis also decreased. The hyphae density measured by filtration is therefore a direct measure of the metabolic potential of the organism.
A new sensor, the “filtration probe,” for quantitative characterization of the penicillin fermentation. II. The monitor of mycelial growth
Authors: Nestaas Erik , Wang Daniel I. C. , Suzuki Hiroaki , Evans Lawrence B.
Published: December 2004

Biomass concentration during penicillin production can be estimated rapidly and with reasonable accuracy using the “filtration probe.” The basis for the measurement is the volume of the filter cake which, in contrast to the conventional “packed‐cell volume” measured by centrifugation, is only moderately affected by the morphology of the mycelia. The influence of the mycelial morphology on the specific filter cake volume [ υ (cm3 cake/g dry cells)] can additionally, to a large extent, be predicted from the (specific) filtration resistance of the broth. During the rapid (exponential) growth period, the specific cake volume is, however, more variable and typically exhibits a transient maximum value. The presence of such a maximum can be explained by a simple model for exponential growth of single mycelial particles. this model is based upon conventional kinetics for hyphae elongation and branching and applies well to experimental data (filtration behavior as well as microscopic studies) provided hyphae fragmentation is negligible (i.e., at high growth rates, μ ≅ μmax).
A CSTR‐hollow‐fiber system for continuous hydrolysis of proteins. Factors affecting long‐term stability of the reactor
Authors: Deeslie W. David , Cheryan Munir
Published: December 2004

Factors affecting the long‐term operational stability of a CSTR‐hollow‐fiber reactor for continuous hydrolysis of proteins were studied. The activity declined in a stepwise manner during a run. Declining from 92% conversion to 60% conversion in about ten hours at a space time of four minutes. Initial decay appears to be due to leakage of small active fragments of the enzyme mixture (Pronase) through the membrane, and later decay due to thermal degradation and loss of activators such as calcium through the membrane. The rate of buildup of unconverted substrate in the reaction vessel was controlled by operational variables, but did not appear to affect the reactor output or the operation of the reactor. The decay of the reactor could be partially compensated for by appropriate manipulation of the space‐time variables.
Acid‐bacterial and ferric sulfate leaching of pyrite single crystals
Authors: Keller Ludwig , Murr L. E.
Published: December 2004

Pyrite single‐crystal cubes were cut, polished. and x‐rayed to produce orientations of (100), (110), (111), and (112). These crystallographically developed surfaces then were prepared to expose an area of 1 cm2, and the remainder of the crystal was coated with an acid‐resistant silicone cement. Crystals with representative orientations then were leached in ferric sulfate solutions adjusted to a pH of 2.3 with H2SO4 containing up to 6 × 103 ppm of Fe3+ at 30 and 55°C. Leaching was also conducted in acid‐bacterial lixiviants containing Thiobacillus ferrooxidans at 30°C and a thermophilic microorganism at 55°C. Surface corrosion and pitting associated with pyrite leaching were examined by scanning electron microscopy. Pyrite leaching in ferric sulfate solutions was observed to be different when compared to acid‐bacterial leaching. Ferric sulfate leaching required nearly 2 × 103 ppm of Fe3+ at 30°C while acid‐bacterial leaching at 30°C occurred without additions of Fe3+, and values of Fe3+ never exceeded 102 ppm. Because of precipitate formation, an accurate assessment of the role of crystallographic orientation on the leaching of pyrite is difficult.
Immobilization of glucose oxidase on sepharose by UV‐initiated graft copolymerization
Authors: D'angiuro L. , Cremonesi P.
Published: December 2004

The performance of a new method of enzyme immobilization based on photochemically initiated direct graft copolymerization was recently investigated. The immobilization reaction can be carried out in a simple way and by carefully selecting the reaction conditions, the enzyme‐graft copolymer can be obtained as the main reaction product. Coupling efficiency of glucose oxidase has been found to depend only on the amount of photocatalyst (FeCl3) fixed on Sepharose used as polysaccharide support. Small quantities of glycidymethacrylate (GMA) (0.25 g/g dry Sepharose) are sufficient but necessary to achieve the best enzyme coupling efficiency (20–40%). Enzyme immobilization occurs very rapidly and the entire reaction occurs within 60 min. Reaction patterns and physicochemical characteristics of the obtained enzyme‐graft copolymers exclude the glucose oxidase entrapment: therefore a covalent attachment mechanism may be proposed. The kinetic parameters of immobilized glucose oxidase (Km′ = 2.0 × 10−2M) are quite similar to those of free enzyme (Km = 1.93 × 10−2M), and no diffusion limitation phenomena are evidenced in samples having different enzyme or polymer content. Lyophilization, thermostability, and long‐term continuous operation also have been investigated. The advantages of this method over that using vinylenzyme copolymerization are discussed.
A study of acetic acid production by immobilized Acetobacter Cells: Oxygen transfer
Authors: Ghommidh C. , Navarro J. M. , Durand G.
Published: December 2004

The immobilization of living Acetobacter cells by adsorption onto a large‐surface‐area ceramic support was studied in a pulsed flow reactor. The high oxygen transfer capability of the reactor enabled acetic acid production rates up to 10.4 g L−1 h−1 to be achieved. Using a simple mathematical model incorporating both internal and external mass transfer coefficients, it was shown that oxygen transfer in the microbial film controls the reactor productivity.
Predominant role of hydrocarbon solubilization in the microbial uptake of hydrocarbons
Authors: Reddy P. G. , Singh H. D. , Roy P. K. , Baruah J. N.
Published: December 2004

Using EDTA and proteolytic enzymes to suppress hydrocarbon solubilization, direct evidence is presented in support of the mechanism of liquid hydrocarbon uptake by microbial cells predominantly from the solubilized or accommodated substrate. EDTA (2–5mM) strongly inhibited growth of three yeast species and one bacterial species on n‐hexadecane and the inhibition was removed by surfactant‐emulsified and surfactant‐solubilized alkane and also by excess addition of Ca2+. EDTA had no inhibitory effect on the growth of the organisms on soluble substrates such as sodium acetate and nutrient broth or on n‐pentane, a volatile alkane which was primarily transported by diffusion from gas phase. EDTA was shown to have no significant effect on the adsorption of cells on alkane drops. EDTA inhibition of growth was considered to be due to suppression of alkane solubilization, brought about by the solubilizing factor(s) produced by cells. It was shown that this chelating agent did not inhibit the growth of yeast on solubilized alkane but strongly inhibited its growth on alkane drops. It was demonstrated that adherent capacity of microbial cell to oil phase was closely related to the state of hydrocarbon emulsification and had no relationship to the ability of organisms to grow on hydrocarbon. Certain proteolytic enzymes inhibited the growth of yeast on alkane, presumably by digesting the alkane solubilizing protein, but not on glucose, and the inhibition was removed by a supply of surfactant‐emulsified and surfactant‐solubilized alkane. Specific solubilization of various hydrocarbon types during growth of the prokaryotic bacterial strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited strain was demonstrated. The specific solubilization of hydrocarbon was strongly inhibited by EDTA, and the inhibition was removed by excess Ca2+. It was concluded that specific solubilization of hydrocarbons is an important mechanism in the microbial uptake of hydrocarbons.
Studies on the characteristics of alginate gels in relation to their use in separation and immobilized applications
Authors: Kierstan M. , Darcy G. , Reilly J.
Published: December 2004

Studies on diffusion of NAD and hemoglobin from calcium and barium gels are reported where alginate grade, concentration, and gel dimensions were varied. These show that NAD diffusion characteristics are unaffected by alginate and ion concentrations; however, hemoglobin diffusion is affected by alginate concentration. Both hemoglobin and NAD diffusion patterns were shown to be affected by alginate gel dimensions. Studies are reported that show that polymannuronic alginate gels posses good porosity characteristics while polyguluronic alginates from gels with lower porosity, specifically with respect to high‐molecular‐weight compounds. These findings are discussed with the view to the use of alginate gels for immobilization, solids separation, and diffusion chromatography techniques.
Effects of ethanol and other alkanols on the kinetics and the activation parameters of thermal death in Saccharomyces cerevisiae
Authors: Leão Cecília , Van Uden N.
Published: December 2004

Ethanol, isopropanol, propanol, and butanol enhanced thermal death in Saccharomyces cerevisiae by increasing ΔS‡, the entropy of activation of thermal death while ΔH‡, the enthalpy of activation, was not significantly affected. The relation between ΔS‡ and alkanol concentration was linear with a different slope for each alkanol: ΔS‡X = ΔS‡0 + CAEX, where X is the alkanol concentration and CAE the entropy coefficient for the aqueous phase defined as increase in entropy of activation per unit concentrations of the alkanol. CAE was correlated with the lipid‐buffer partition coefficients of the alkanols while CME, the entropy coefficient for the lipid phase, was nearly identical for the four alkanol and averaged 37.6 entropy units per mole of alkanol per kilogram of membrane. As predicted by these results, the specific death rates (Kd) at constant temperature were an exponential function of the alkanol concentration and behaved in agreement with the following equation: In KXd = In K0d + (CAE/R)X, where R is the gas constant. It was concluded that the alkanols enhanced thermal death through nonspecific action on membrane structure.