bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and application of polymer‐entrapped enzymes and microorganisms in microbial transformation processes with special reference to steroid 11‐β‐hydroxylation and Δ1‐dehydrogenation
Authors: Mosbach Klaus , Larsson Per‐Olof
Published: May 2005

Fungal cells fromCurvularia lunatawere entrapped in a crosslinked polyacrylamide gel. The gel‐cells obtained as granules were applied in the microbial transformation of Reichstein compound S leading to cortisol through an 11‐β‐hydroxylation step. Some kinetic studies of this conversion using gel‐cells were carried out. In addition, it was shown that gel‐cell granules which had lost part of their 11‐β‐hydroxylase activity on storage could be reactivated yielding preparations with increased activity.

FromCorynebacterium simplexa steroid dehydrogenase catalyzing the Δ1‐ dehydrogenation of cortisol leading to prednisolone was isolated and partially purified. The preparation was entrapped in a crosslinked polyacrylamide gel and the gel‐enzyme granules obtained used in steroid dehydrogenation processes.
The influence of high substrate concentrations on microbial kinetics
Authors: Edwards Victor H.
Published: May 2005

High substrate concentrations inhibit growth and may distort the metabolism of microorganisms. Mechanisms causing substrate inhibition are discussed and used to derive several mathematical models representative of the entire concentration range, including stimulation of growth by low substrate concentrations. These kinetic models are tested with a variety of batch culture measurements of specific growth rate and respiration rate at widely‐ranging substrate concentrations. Using one of the kinetic models, equations are developed for batch, continuous, and exponential‐feed reactors. Comparison of results obtained in continuous culture with results from exponential‐feed culture systems is shown to offer a novel experimental method for evaluating the effect of the cell age distribution on the properties and metabolic activity of a culture.
Growth models of cultures with two liquid phases: IV. Cell adsorption, drop size distribution, and batch growth
Authors: Erickson L. E. , Fan L. T. , Shah P. S. , Chen M. S. K.
Published: May 2005

In this work, a mathematical model which can be used to describe butch growth in fermentations with two liquid phases present is developed for systems in which the growth limiting substrate is dissolved in the dispersed phase. The model takes into account the drop size distribution, the rate of adsorption of cells on the drop surface, the rate of desorption of cells from the drop surface, substrate transport between phases, phase equilibrium, and growth kinetics. The model also considers the effect, of coalescence and redispersion of oil drops in the system. It is assumed that the composition of the dispersed phase is such that substrate utilization from it causes little or no change in the interfacial area. A discrete uniform distribution and a discrete normal distribution which is obtained from an experimental distribution curve are used as drop size distributions. Simulation results are obtained for a wide range of parameter values using the IBM S/360 Continuous System Modeling Program.
Optimization of batch fermentation processes. II. Optimum temperature profiles for batch penicillin fermentations
Authors: Constantinides Alkis , Spencer Jordan L. , Gaden Elmer L.
Published: May 2005

Optimization methods based on the continuous maximum principle and the calculus of variations were used to calculate optimum temperature profiles for batch penicillin fermentations. These methods were first applied to several general models to develop effective techniques for the numerical solution of the equations. Subsequently, these methods were applied to two particular models, derived from experimental data, and the optimum temperature profiles were determined. The results indicated that an improvement, in penicillin yield of about 15% was possible if the optimum temperature profiles were followed.
The use of methane for production of bacterial protein
Authors: Bewersdorff Margareta , Dostálek Milan
Published: May 2005

Single cell protein production was studied in a mixed bacterial culture grown in methane using batch and continuous culture techniques. Overall productivity was found to be higher in the continuous culture which gave a maximum productivity value p = 0.15 g/l/h. Methane and oxygen were consumed in the relation 1 : 1.7. Yield coefficients for methane, oxygen, and ammonium chloride were Y = 0.90, Y = 0.26, and Y = 0.14. The crude protein content of the biomass was 71%.
Kinetics of diffusion‐coupled fermentation processes: The conversion of cellulose to protein
Authors: Ross L. W. , Updegraff D. M.
Published: May 2005

A combination of Fickian diffusion and Michaelis–Menten kinetics is proposed to describe the rate of diffusion‐coupled biochemical reactions. This postulate leads to a nonlinear mathematical model which is solved by a perturbation technique. The result is a relation which permits identification of zones of relative diffusion or reaction influence. The conversion of cellulose to protein by Myrothecium verrucaria is a heterogeneous process that is well‐suited to this type of analysis, although the data requirements are severe.
Growth models of cultures with two liquid phases. V. Substrate dissolved in dispersed phase—experimental observations
Authors: Prokop A. , Erickson L. E. , Paredes‐Lopez O.
Published: May 2005

The effects of inoculum size, dispersed phase volume and substrate concentration on the batch growth of Candida lipolytica are investigated in a model system composed of n‐hexadecane dissolved in dewaxed gas oil. Tabular values and parameters are presented for 16 different experiments. All of the batch growth curves exhibited a linear growth region with the length of the region ranging from 1.5 to 9.5 hours. The rate of linear growth varied both with change in dispersed phase volume and initial dispersed phase substrate concentration. A qualitative analysis of the results is presented and possible explanations for the observed linear growth rates are discussed.
A chemostat study of ethanol inhibition
Authors: Zines D. O. , Rogers P. L.
Published: May 2005

The mode of ethanol action on both the steady‐state and the dynamic properties of K. aerogenes was investigated using a nitrogen‐limited chemostat. Reduction in the maximum growth rate (μm) suggests that noncompetitive enzyme inhibition could occur, but Lineweaver–Burk analysis showed the inhibition to be more complex. A consistent mechanism of inhibition was established for 0–3% v/v ethanol. Warburg manometric experiments indicated that inhibition occurred in pathways located in the intact cell wall. Frequency response analysis, using sinusoidal variations in the dilution rate showed that ethanol increased the time constant of the metabolic parameter, QAC. The system was stable in the presence of ethanol and showed no evidence of oscillations following a disturbance.
Preparation of a NAD(H)‐polymer matrix showing coenzymic function of the bound pyridine nucleotide
Authors: Larsson Per‐Olof , Mosbach Klaus
Published: May 2005

To a Sepharose gel the pyridine nucleotide NAD(H) has been bound using dicyclohexyl carbodiimide. In order to improve the steric availability of the nucleotide for added soluble enzymes such as dehydrogenases, a spacer molecule, ε‐amino caproic acid, was inserted between the carbohydrate matrix and the nucleotide. The obtained preparation contained 56 μmoles NAD+/g dry polymer. The obtained matrix‐bound NAD(H) was accepted as coenzyme by added lactate dehydrogenase. These preparations were still active after storage for several weeks at 4° C and could be used repeatedly without loss of activity. This represents the first necessary step taken in the preparation of compact closed systems consisting of “enzyme–coenzyme–coenzyme‐regenerating enzyme” bound to individual polymer beads; such systems eliminate the need for continuous coenzyme addition.
Chemical and biological aspects of a new family of phosphorus‐containing antibiotics
Authors: Slusarchyk William A.
Published: May 2005

The chemical, physical, and biological properties of a group of phosphorus‐containing antibiotics are reviewed. Included in this family of antibiotics are the following compounds or mixtures of compounds: diumycin, macarbomycin, moenomycin, prasinomycin, 803GRP, 11,837RP, and 19,402RP. Among the aspects discussed are: antimicrobial activity in vitro, long duration of activity, toxicity, use in animal nutrition, cross resistance, mode of action, chemical and physical properties, and degradation studies.
Multiphase catalysis. II. Hollow fiber catalysts
Authors: Rony Peter R.
Published: May 2005

A theory of diffusion control within hollow fiber catalysts is derived for three different types of coordinate geometries: Cartesian, cylindrical, and spherical. Effectiveness factors are calculated and formulas for reactant conversion in both a fixed‐bed and a contimunuous‐feed stirred‐tank reactor are derived. The apparent Michaelis constant, Km′, is a measure of the amount of diffusion control within the catalysts. When Km′ is equal to Km, the true Michaelis constant, there is no diffusion control. In all other cases Km′ is greater than Km. Hollow fibers are attractive alternatives to spherical microcapsules for the encapsulation of enzymes.
Effect of pH on the growth cycle of HeLa cells in batch suspension culture without oxygen control
Authors: Barton M. E.
Published: May 2005

HeLa cells have been cultured at different controlled pH levels in batch suspension culture with open gas phase. Continuous monitoring of the dissolved oxygen tension throughout the culture cycle reveals a characteristic pattern of variation which correlates with various aspects of growth and carbohydrate metabolism. The effect of pH, size, and physiological state of the inoculum on this pattern have been determined, and the results are discussed in terms of a theoretical respiratory rate equation.
Influence of surface active agents on oxygen absorption to the free interface in a stirred fermentor
Authors: Bull Daniel N. , Kempe Lloyd L.
Published: May 2005

Liquid phase coefficients were measured for the absorption of oxygen from air to the free interface in stirred vessels. Coefficients for absorption into soft water were independent of the instantaneous dissolved oxygen concentration. Coefficients for absorption into soft water containing a surface active agent were strongly dependent on the instantaneous dissolved oxygen level. The degree of nonlinearity of the coefficients was a function of the rate of agitation of the liquid. The coefficients were independent of the amount of surface active agent added above a very low level. Absorption coefficients for bubble aeration in the same vessels were independent of dissolved oxygen concentration even when the surface active agent was present.
Release of enzymes from bakers' yeast by disruption in an industrial homogenizer
Authors: Follows Maggie , Hetherington P. J. , Dunnill P. , Lilly M. D.
Published: May 2005

The rates of release of 7 enzymes from bakers' yeast have been measured. The disruption process did not cause loss of activity of these enzymes. The various operating pressures, temperatures, and initial yeast concentrations used did not affect the rates of enzyme release relative to protein release. The release of acid phosphatase and invertase was faster than the overall protein release. Alcohol, glucose‐6‐phosphate, and 6‐phosphogluconate dehydrogenases were released slightly faster or at the same rate as the overall protein and alkaline phosphatase and fumarase were released more slowly. These observations correlate well with the reported locations of these enzymes in the yeast cell.
Oxygen mass transfer and oxygen respiration rate measurements utilizing fast response oxygen electrodes
Authors: Heineken F. G.
Published: May 2005

Oxygen transfer coefficient and oxygen respiration rate measurements in stirred tank reactors or fermentors have been carried out utilizing currently available dissolved oxygen electrodes. Techniques based on previously derived theory1 have been put to experimental tests and found to adequately describe the oxygen transfer phenomena observed in air–water systems and a fermenting broth.
Controlled supply of trace amounts of oxygen in laboratory scale fermentations
Authors: Haukeli Alf D. , Lie Sturla
Published: May 2005

A detailed study of anaerobic yeast fermentations requires controlled addition of minor amounts of oxygen to the fermentor. A method for supplying small‐scale fermentations with millimolar amounts of oxygen is described. The controlled addition is accomplished by diffusion of oxygen through silicone tubing carrying nitrogen to the fermentor. Sulfite values of the fermentation system are given for different gas velocities and lengths of silicone tubing. Two experiments are outlined in which this technique is applied and the possible energy yield from oxydative phosphorylation is discussed.
Electrochemical measurements with glucose oxidase immobilized in polyacrylamide gel: Constant current voltametry
Authors: Wingard Lemuel B. , Liu C. C. , Nagda Niren L.
Published: May 2005

Constant current voltametry was shown to be a suitable method for evaluation of electrodes containing immobilized oxidative enzymes as catalysts. The half‐cell potential for the oxdidation of D‐glucose at constant pH was measured at a series of constant dc currents, using glucose oxidase immobilized in a polyacrylamide gel‐platinum gauze matrix as catalyst. Over the range studied the potential versus current data were linear and could be extrapolated to give the open‐circuit half‐cell potential at zero current. The difference between the measured potential and the open‐circuit potential at a constant current was indicative of the loss in useful voltage due to concentration gradients within or adjacent to the enzyme electrode assembly. The relationship between the open‐circuit potential and the pH of the reaction mixture was linear with a slope of −0.056, in good agreement with the predicted slope of −0.061.
Continuous synchronous culture of Tetrahymena pyroformis
Authors: White Robert W. , Howell John A.
Published: May 2005

Tetrahymena was continuously cultivated in a series of stirred tank reactors with recycle. By holding part of the reactor train at a higher temperature than the remainder a synchronizing influence was introduced into the cells' environment. The system resulted in division occurring preferentially in a small contiguous group of the reactors, this effect being observed in both the number of cells found in each reactor and also their size distribution.
Effect of additives on mass transfer in turbine aeration
Authors: Benedek Andrew , Heideger William J.
Published: May 2005

Mass transfer coefficients and interfacial areas were determined for the aeration of aqueous solutions in a turbine agitated vessel. The mass transfer coefficients measured for water without additive and for sodium chloride solutions matched very well to measurements in the literature for air bubbles of the same diameter in free rise. Thus the only effect of agitation was to determine the bubble size which then in turn set the coefficient. Two surface active agents were studied: sodium dodecyl sulfate and Dow Corning Antifoam C. The rate of mass transfer increased with the former additive but decreased with the latter; however, the mass transfer coefficient was the exact same function of bubble diameter in both cases and the different rates are attributed to the quite different effects on interfacial area.
A continuous flow automatically recording respirometer
Authors: O'Brien W. J. , Agnew R. W. , Chun M. R.
Published: May 2005

A respirometer suitable for continuous operation over extended periods of time is described. Oxygen is supplied to the culture by the electrolysis of water. The quantity of oxygen produced by electrolysis within any specified time interval is automatically printed on a tape. This record is combined with a continuous recording of the concentration of dissolved oxygen entering and leaving the reactor to produce a mass balance for oxygen in the system. Details on respirometer construction and operation are presented.
Deep‐tank culture of blue‐green algae in H2O and D2O
Authors: Taecker R. G. , Crespi H. L. , DaBoll H. F. , Katz J. J.
Published: May 2005

A 160‐liter stainless steel algal growth tank has been constructed and has been used essentially continuously for over three years. Filamentous and unicellular blue‐green algae as well as a photosynthetic bacterium have been cultured using both ordinary and heavy water (99.8 atom % 2H). By using a recycling technique, yields as high as 25 g/liter of 2H2O have been obtained.
Response of continuous cultures to stimuli in glucose feed rate and dilution rate
Authors: Regan D. L. , Roper G. H. , Moss F. J.
Published: May 2005

The response of continuous cultures of yeast was investigated following step disturbances in glucose feed rate and dilution rate.

The responses of the culture to the stimuli were oscillatory. The oscillatory responses were explained in terms of cell synchrony which was induced by the step change. An understanding of continuous cultures to stimuli was made possible with an appreciation of the inherently oscillatory events occurring in the single cell cycle between one mitosis and the next. Step changes in glucose feed rate and dilution rate induced a partial synchrony, which enabled the inherently oscillatory behavior of the individual cells to be made observable in the culture as a whole.
Continuous fermentation to produce xanthan biopolymer: Effect of dilution rate
Authors: Silman R. W. , Rogovin P.
Published: May 2005

Single‐stage continuous fermentations to produce xanthan gum have been run at dilution rates (D) from 0.023 to 0.196 hr−1. Xanthan production rate (XPR) was a function ofD. XPR increased from 0.34 g/hr/kg atD= 0.023 hr−1to the maximum 0.84 g/hr/kg atD= ca. 0.15 hr−1. AtD> 0.15 hr−1XPR decreased and at the highestDstudied (0.196 hr−1) was 0.69 g/hr/kg. Yield of xanthan from glucose consumed was 81–89%. Steady states ended between 6.5 and 8.7 turnovers when a variant strain occurred.
Kinetics of protein release from yeast sonicated in batch and flow systems at 20 kHz
Authors: James C. J. , Coakley W. T. , Hughes D. E.
Published: May 2005

The release constant, k, of brewers yeast sonicated at powers up to 200 W at 20 kHz has been shown to be independent of cell concentration up to values of 60 g made up to 100 ml. It is inversely proportional to the volume of the treatment vessel in the range 75 to 450 ml, and almost proportional to the input acoustic power from 60 to 195 acoustic watts. A flow system is described and a relationship linking protein release, flow rate, and the protein release constant, determined from batch experiments, is derived. Good agreement between the theoretical prediction of protein release and experimental results with the flow system was obtained.
Oil drop size distribution in hydrocarbon–water systems
Authors: Podlech Pablo A. Sanchez , Borzani Walter
Published: May 2005

In this work, a radiometric method is used for the determination of the oil drop size distribution in agitated hydrocarbon–water systems. The influence of the counter position, the oil concentration, and the rotation speed of impeller were studied. An experimental parameter is proposed for the definition of the drop size distribution. It was observed that an unsymmetrical distribution represents the drop size distribution better than the normal distribution law.
Degradation of ribonucleic acid in Candida lipolytica: Extraction of ribonucleic acid degrading enzymes
Authors: Imada Akira , Sinskey Anthony J. , Tannenbaum Steven R.
Published: May 2005

We developed an efficient and simple method for RNase extraction from Candida lipolytica cells which consists of predrying the cells with solvents and incubating them for 8 to 15 hr at 37 to 45°C in a slightly acid buffer which contains EDTA or salts. This method is called Solvent Dehydration Buffer Extraction (SDBE) procedure. Predrying with acetone or ethanol, or by lyophilization, followed by washing with acetone or ethylacetate gives the most efficient RNase extraction. The yield and specific activity obtained by this extraction procedure are higher than by any other method examined. An apparent 1.5‐ to 2.0‐fold activation of RNase occurred during the SDBE process. Activation of RNase in homogenates obtained by grinding fresh cells is also observed with EDTA or acetate buffer. The SDBE procedure works efficiently regardless of growth phase for Candida lipolytica, and works also with other Candida yeasts.
The relationship between hydrogen gas and butanol production by Clostridium saccharoperbutylacetonicum
Authors: Brosseau James D. , Yan Jwo‐Yee , Lo K. Victor
Published: May 2005

Two simultaneous fermentations were performed at 26°C with simultaneous inocula using Clostridium saccharoperbutylacetonicum. Fermentation 1 prevented the gas formed by the biomass from escaping the fermentor while 2 allowed the gas formed to escape. Fermentor 1 provided for the production of butanol, acetone, and ethanol, while when the H2 formed was allowed to escape with fermentor 2, neither butanol nor acetone were produced. Ethanol was also formed in both fermentors and began along with the initial growth of biomass and continued until the fermentations were complete. Butanol and acetone production began after biomass growth had reached a maximum and began to subside. The butanol‐acetone‐ethanol millimolar yields and ratios were 38:1:14 respectively. The fermentor 2 results show that a yield of 2.1 L H2, 93 or 370 mmol H2/mol glucose, was formed only during the growing stage of growth; neither butanol nor acetone were produced; ethanol was formed throughout the fermentation, reaching a yield of 15.2 mmolar. It appears that hydrogen gas is required for butanol production during the resting stage of growth.
A multispecies biofilm model
Authors: Wanner O. , Gujer W.
Published: May 2005

Using a continuum approach and observing conservation principles, an analytical mathematical model of microbial interaction in biofilms was developed. The model predicts changes in biofilm thickness and describes the dynamics and spatial distribution of microbial species and substrates in the film. It allows for biomass detachment due to shear stress and sloughing, external mass transfer limitations, as well as variations in substrate concentrations in the bulk liquid. A computer implementation of the model is provided using an example of heterotrophicautotrophic competition to illustrate how the observed phenomena can be numerically reproduced and indicating how they might affect overall biofilm performance.
A measuring system for biotechnical processes based on discrete methods of estimation
Authors: Staniškis J. , Simutis R.
Published: May 2005

An adaptive measuring system of the main variables of biotechnical processes based on the theory of estimation is elaborated upon here. All stages of system synthesis are considered. It is shown that for an adaptive measuring system all a priori information on modelling and measurement noise and process mathematical models must be used. The data of direct and indirect measurements are used for estimating the main variables. The performance of the proposed measuring system was checked using imitative modelling.
The kinetics of protein precipitation by different reagents
Authors: Chan M. Y. Y. , Hoare M. , Dunnill P.
Published: May 2005

The kinetics of precipitation of soya protein has been examined in a tubular flow reactor with the precipitants, ammonium sulfate, ethanol, divalent calcium, and sulfuric acid. The precipitate growth profiles obtained in all cases showed the rapid formation of a precipitate phase and the attainment of a final size within 16 s. The final mean particle diameter dm varied with precipitating agent used in the order: sulfuric acid (12.5 μm) > ethanol (7.5 μm) ≈ calcium ion (7.2 μm) > ammonium sulfate (3.1 μm). In the case of ethanol precipitation, changes in the design of the contacting section of the reactor led to differences in the precipitate growth curve. Protein solubility curves are also presented, and with the reactor data, they provide a convenient method for assessing the effect of precipitating agent on the design of protein precipitation reactors.
A computer model for the growth and differentiation of a fungal colony on solid substrate
Authors: Georgiou G. , Shuler M. L.
Published: May 2005

Mold growth and differentiation are closely related to the formation of secondary products. In solid‐substrate fermentations this interrelationship is often more completely realized than in submerged cultures. Solid substrate reactions are used commercially in a limited manner in the western world, but are relatively common in Asia. Basic studies in solid‐substrate fermentation should yield results applicable to all types of commercial mold fermentations for the production of a secondary product. This paper presents a relatively simple model for the growth of a mold colony on a solid surface with a defined medium utilizing glucose. Unlike submerged cultures the model must account for both cellular differentiation and the spatial heterogeneity in the system. Model parameters were estimated independently using literature values. The results of the simulation studies suggest that mass transfer limitations are at least partially responsible for the proliferation of differentiated structures on solid substrates as compared to liquid cultures. Since the concentration profile depends on the depth of the substratum, conditions that enhance conidia production can be achieved by controlling the depth of the solid medium.
Pressure drop in a packed bed with a liquid of variable viscosity: The case of dextrin hydrolysis by immobilized glucoamylase
Authors: Kim Kyung Hoe , Chang Ho Nam
Published: May 2005

The activity of an immobilized enzyme in a packed bed is monitored for the change in a substrate conversion with time. But pressure drop in the packed bed with immobilized glucoamylase can serve as an indirect indicator for the changes in the conversion and activity of the immobilized enzyme. The method is simple and the change can be monitored continuously. This method can be generally applicable to systems where the viscosity of a substrate changes with its conversion.
A novel method of determination of the internal enzyme distribution within porous solid supports and the deactivation rate constant
Authors: Do D. D. , Hossain M. M.
Published: May 2005

This article presents a method for determining the rate constant for deactivation and the internal distribution of immobilized enzyme. This method makes use of the parallel deactivation process in a diffusion‐controlled regime, in which the internal activity profile behaves like a penetration front. This front basically traces through the initial active enzymatic profile, and one can determine the internal profile and the rate constant for deactivation from the experimentally observable bulk concentration versus time. This method is applied to the experimental data of the system of hydrogen‐peroxide‐immobilized catalase on controlled pore glass and Si–Al particles.
Kinetics of anaerobic purification of industrial wastewater
Authors: Bolle W. L. , van Breugel J. , van Eybergen G. C. , Kossen N. W. F. , van Gils W.
Published: May 2005

As a part of the development of an integral mathematical model describing the up‐flow anaerobic sludge blanket (UASB) reactor, the kinetics of the conversion of organic wastes has to be known. We compared the Monod model with the model proposed by Andrews et al. Together with the assumption that the substrate for the anaerobic bacteria is formed by nonionized, volatile fatty acids, the Andrews model is able to describe substrate inhibition and reactor failure due to pH changes.

From four batch experiments, with different concentrations of microorganisms, it could be concluded with a reliability of over 95% that the monod model was inadequate and Andrews' model was adequate to describe the measurements. Standard statistical techniques like the X2‐ and the F‐test were used for this purpose.

From a parameter sensitivity analysis for the Andrews model it followed that the maximum specific growth rate μ of the bacteria and the inhibition constant K1 are the parameters which influence the system most. Thus, these parameter were determined experimentally and most accurately. The results are:

The other parameters were taken from literature. From calculation of the Thiele modulus for the particles it follows that transport limitation of the substrate in the flocus is not significant. The efficiency η is 0.85 in the worst case.
Effects of periodic change in pressure and dissolved‐oxygen concentration on the incubation characteristics of Pseudomonas aeruginosa
Authors: Kataoka Hiroshi , Sato Seigo , Mukataka Sukekuni , Namiki Atsushi , Yoshimura Keiichiro , Takahashi Joji
Published: May 2005

Experiments were carried out to identify an efficient procedure for decreasing the amount of excess sludge in deep aeration columns. Incubation characteristics, especially cellular yield, are closely related to excess sludge, maximum specific growth rate, and chemical oxygen demand. They were measured here for the bacterium Pseudomonas aeruginosa, which tends to be predominant in sewage treatment, at a pressure remaining constant or periodically changing in the range of 1–6 atm (abs.). Cellular yields tended to decrease over 1–2 min pressure cycles; in steady operation they decreased considerably with increasing pressure or dissolved oxygen concentration. Maximum specific growth rates were moderately affected by periodic changes in pressure or dissolved oxygen concentration but markedly affected in the higher concentration range under steady operation. Substrate consumption rates on the other hand, were little affected in either case. The values of chemical oxygen demand ranged from 220 to 250 mg/L, and were thus nearly constant.
Production of acetic acid by Clostridium thermoaceticum in batch and continuous fermentations
Authors: Sugaya K. , Tusé D. , Jones J. L
Published: May 2005

Batch and continuous fermentations with Clostridium thermoaceticum (ATCC 39073) using automatic pH control were conducted. The value of μmax obtained from batch fermentation was about 0.14 h−1; acetate yield, which was both growth and non‐growth associated, was about 2 mole of acetic acid/mole of glucose, compared with a theoretical maximum value of 3. This low yield, compared with literature data, may be explained by glucose loss through a combination of degradation routes. Continuous fermentation could be sustained for 1600 h or more without contamination problems. Continuous fermentation at high dilution rates indicates that μmax may be well above 0.17 h−1 when fresh feed medium is used. Acetate yields in continuous fermentation were about 77% of theoretical or 2.3 mole of acetic acid/mole of glucose.
Induction and elimination of oscillations in continuous cultures of Saccharomyces cerevisiae
Authors: Parulekar Satish J. , Semones Gary B. , Rolf Michael J. , Lievense Jefferson C. , Lim Henry C.
Published: May 2005

Continuous cultures of Saccharomyces cerevisiae are known to exhibit oscillatory behavior in the oxidative region. Important findings of a series of experiments conducted to identify the causes for initiation of and the means for elimination of oscillations in these cultures are reported in this paper. These oscillations are seen to be connected to the growth kinetics of the microorganism and are induced at very low glucose concentrations and at dissolved oxygen (DO) levels that are neither high nor low (DO values between 20 and 78% air saturation at a dilution rate of 0.2 h−1 and pH of 5.5 at 30°C). The oscillatory behavior is encountered over a range of dilution rates (0.09–0.25 h−1 at 30°C for pH = 5.5 and DO = 50% air saturation). The oscillations can be eliminated by raising the DO level above a critical value or by lowering the DO level below a critical value.
Kinetic considerations about the study of alcoholic fermentations of starch hydrolysate
Authors: Converti Attilio , Perego Patrizia , Borghi Marco Del , Parisi Federico , Ferraiolo Giuseppe
Published: May 2005

Alcoholic fermentations of starch hydrolysate by two different yeast strains, Saccharomyces cerevisiae(var. Vinal) and Saccharomyces oviformis(IMAP 383), have been studied in batch runs. In order to evaluate the different inhibition phenomena due to both substrate and product, a new kinetic equation is suggested.
Electroenzymatic reactors with coenzyme regeneration: A theoretical approach
Authors: Bergel Alain , Comtat Maurice
Published: May 2005

A comparison of the relative performance of production techniques using coenzyme or cofactor electrochemical regeneration demonstrates the superiority of those processes in which the enzymatic reaction and the regeneration are conducted in the same reactor as opposed to those in which the reaction and regeneration are separated. For the former type of reactor, a method of calculation is proposed. This method is based on the solution of equations which describe the phenomena in modules representing three areas: the surface of the electrode, a layer where occur simultaneously the transport of material and the enzymatic reaction, and the bulk of the solution. This method is suggested for three types of reactor: those in which an enzyme solution is held close to an electrode by a semipermeable membrane, those in which an enzyme‐charged membrane is in contact with an electrode, and those in which the enzyme is in solution in the vessel into which the electrode is dipped.
Optimization of CSTRs in series by dynamic programming
Authors: Ong S. L.
Published: May 2005

This article concerns the development of a simple yet effective procedure for optimizing the design of a reactor system employing CSTRs in series. The basic approach used in this work was to translate the problem of reactor design to a mathematical programming model. The resulting model was then solved by dynamic programming. The procedure was tested on an IBM 3033 computer and an IBM PC‐compatible machine, the CORONA PC‐II microcomputer. The results of this study indicate that the optimization procedure developed is very effective.
Utilization of spline functions for smoothing fermentation data and for estimation of specific rates
Authors: Oner M. D. , Erickson L. E. , Yang S. S.
Published: May 2005

A response surface method of smoothing fermentation data with spline functions is presented. The available electron balance is used to optimally select the values of the smoothing parameters associated with the spline functions. The method is applied to six sets of anaerobic fermentation data in which pure and mixed cultures are grown in batch followed by fed batch culture.Lactobacillus bulgaricusandStreptococcus thermophilusare cultured on 3% dry milk. Measured concentrations of biomass, lactose, galactose, lactic acid, and other acid products are smoothed using spline functions. Values of specific growth rate, specific lactose consumption rate, specific galactose formation rate, and specific acid product formation rate are estimated and the consistency of the results is examined using the available electron balance. The results show that the method works reasonably well, but that an upper bound should be used for the smoothing parameters to obtain accurate estimates of the derivative quantities.
Estimation of the true growth yield and maintenance coefficient for yoghurt cultures
Authors: Oner M. D. , Erickson L. E. , Yang S. S.
Published: May 2005

Point and 95% confidence interval estimates of the true growth yield and maintenance coefficient are reported for four pure cultures andtwo mixed cultures of Lactobacillus bulgaricus and Streptococcus thermophilus grown anaerobically on 3% nonfat dry milk using batch followed by fed batch culture. An improved method of data analysis, which includes separate analysis of the exponential growth region and a new method of selecting smoothing spline functions, is utilized. The parameter estimation results are compared with the theoretical maximum yields for one and two moles of ATP produced per mole of glucose and to the growth yield estimated from the exponential growth region analysis.
Optimal control of substrate concentrations in bioreactors with separated sensors
Authors: Oǧuztöreli M. N. , Özüm Baki , Gerson Donald F.
Published: May 2005

Many of the sophisticated sensors desirable for monitoring bioreactors cannot be placed in the bioreactor either because they are not steam sterilizable or because they require nonphysiological operating conditions. Such sensors can be used if they are separated from the bioreactor. Separation of the sensor from the bioreactor causes a time lag in data acquisition. This results in several complexities in the development of an appropriate and stable feedback control system based on a separated sensor. This paper analyzes the optimal control of a bioreactor with a separated sensor without a time lag and analyzes the feedback control (but not necessarily the optimal control) with a time lag. Simulation results indicate that this type of analysis could be extended to more general bioreactor operating conditions.
Preparation of L‐aspartic acid by means of immobilized Alcaligenes metalcaligenes cells
Authors: Vojtšek V. , Guttrnann T. , Bárta M. , Netnral J.
Published: May 2005

Two types of biocatalysts based on immobilized cells of Alcaligenes metalcaligenes exhibiting aspartate ammonia‐lyase activity (EC 4.3.1.1) were developed for the enzymic preparation of L‐aspartic acid from ammonium fumarate. The first type of the biocatalyst consists in individual covalently crosslinked and permeabilized cells(I), while the second type is represented by cell aggregates (II). For the above preparation, biocatalyst I can be used only discontinuously in a mixed reactor. After termination of the reaction between individual cycles of its use, the biocatalyst is returned to the reactor in the form of a highly concentrated cell suspension or paste. Biocatalyst II can be used discontinuously or continuously in a fixed‐bed column of the catalyst. The effects of pH, substrate concentration and temperature on the reaction velocity and effectivity of enzymic conversion was investigated. Optimal parameters of the reaction are as follows: pH 8.5, initial substrate concentration, 1.35 mol/L, temperature for discontinuous process, 37°C, and temperature for continuous process, 25°C. Under these conditions the enzymic conversion of substrate to product is quantitative. Under optimal toring conditions, the specific activity of both catalysts does not change within a period of one year. The operational half‐life of the biocatalyst II during continuous use in a fixed‐bed column of the catalyst under standard reaction conditions depends on the quality of the substrate. The discontinuous preparation of L‐asparatic acid with the aid of biocatalyst I and continuous preparation of this product with the aid of biocatalyst II have been verified under pilot‐plant conditions.
INT–dehydrogenase test for activated sludge process control
Authors: Lopez Juan M. , Koopman Ben , Bitton Gabriel
Published: May 2005

Dehydrogenase activity assay of activated sludge using the redox dye 2‐(p‐iodophenyl)‐3‐(p‐nitrophenyl)‐5‐phenyltetrazolium chloride (INT) was investigated. INT‐dehydrogenase activity (INT–DHA) was directly proportional to INT dosage and inversely proportional to bio‐mass concentration over limited ranges. INT dosages exceeding 2.5m/M were toxic to dilute activated sludge suspensions. INT–DHA was greatest near pH 9, whereas the peak oxygen uptake rate (OUR) occurred at pH 8. Both INT–DHA and OUR varied inversely with sludge age, but INT–DHA was the more sensitive of the two parameters to this variable. Consistently good and highly significant correlations between INT–DHA and OUR of chlorine stressed activated sludge were found at sludge ages ranging 2.2–7.0 days.
Measuring oxygen diffusion coefficients with polarographic oxygen electrodes. II. Fermentation Media
Authors: Ho Chester S. , Ju Lu‐Kwang , Ho Chia‐Tie
Published: May 2005

Fermentation media consist of a large number of chemicals which composition undergoes alteration during the course of fermentations. In consequence, the conventional methods and correlations for gas diffusion coefficient measurement and prediction cannot be easily applied to such systems. Oxygen diffusion coefficients have been measured in simulated chemical systems as well as in complex solutions of nutrient broth, using the polarographic technique introduced in a previous article. It is identified that sugars and salts are the major factors influencing oxygen diffusion coefficients in these aqueous fermentation media. The effect of salts on oxygen diffusion coefficients in electrolyte solutions has been found to be well correlated with the square root of total ionic strength of electrolyte solutions. The individual effect of glucose and its combined effect with salts are explored in order to reach rational correlations capable of predicting oxygen diffusion coefficients in synthetic fermentation media. For aqueous solutions of glucose plus salts, it is observed that the log‐additive relationship can be used to account for the combined effect. Finally, a linear correlation has been established in measuring oxygen diffusion coefficients in aqueous solutions having different concentrations of nutrient broth.
Immobilization of Acetobacter acoti on cellulose ion exchangers: Adsorption isotherms
Authors: Bar Raphael , Gainer John L. , Kirwan Donald J.
Published: May 2005

The adsorptive behavior of cells of Acetobacter aceti, ATCC 23746, on DEAE‐, ECTEOLA‐, TEAE‐, and DEHPAE‐cellulose ion exchangers in a modified Hoyer's medium at 30°C was investigated. The maximum observed adsorption capacities varied from 46 to 64 mg dry wt/g resin. The Langmuir isotherm form was used to fit the data, since the cells formed a monolayer on the resin and exhibited saturation. The equilibrium constant in the Langmuir expression was qualitatively correlated with the surface charge density of the resin. The adsorption was also “normalized” by considering the ionic capacities of the resins. The exceptionally high normalized adsorption capacity of ECTEOLA‐cellulose, 261 mg dry wt/meq, may be explained by an interaction between the cell wall and the polyglyceryl chains of the exchanging groups in addition to the electrostatic effects. The effect of pH on the bacterial adsorption capacity of ECTEOLA‐, TEAE‐, and phosphate‐cellulose resins was studied and the pl of the bacteria was estimated to be 3.0.
Enzyme immobilization via monoclonal antibodies I. Preparation of a highly active immobilized carboxypeptidase A
Authors: Solomon B. , Koppel R. , Pines G. , Katchalski‐Katzir E.
Published: May 2005

A novel method for the preparation of highly active immobilized enzymes is described. It is based on the binding of enzymes to suitable carriers via monoclonal antibodies, which bind to the enzyme with high affinity without affecting its catalytic activity. The applicability of the method forwarded has been illustrated by the preparation of two samples of highly active immobilized carboxypeptidase A (CPA) preparations as follows: A mouse monoclonal antibody (mAb 100)to CPA that binds to the enzyme with a high‐affinity constant without affecting its catalytic activity was prepared, purified, and characterized. Covalent binding of this monoclonal antibody to Eupergit C (EC) or noncovalent binding to Sepharose–protein A (SPA)yielded the conjugated carriers EC‐mAb and SPA·mAb, respectively, which reacted specifically with CPA to give the immobilized enzyme preparations EC‐mAb·CPA and SPA·mAb·CPA displaying full catalytic activity and improved stability. At pH 7.5 and a temperature range of 4–37°C an apparent binding constant of ∼108M−1 characterizing the interaction of CPA with EC‐mAb and SPA·mAb, was obtained. To compare the properties of EC‐mAb·CPA and SPA·mAb·CPA with those of immobilized CPA preparations obtained by some representative techniques of covalent binding of the enzyme with a corresponding carrier, the following immobilized CPA preparations were obtained and their properties investigated: EC‐CPA (I), a preparation obtained by direct binding of EC with CPA; EC‐NH‐GA‐CPA (II), a derivative obtained by covalent binding of CPA to aminated EC via glutaraldehyde; EC‐NH‐Su‐CPA (III), a CPA derivative obtained by binding the enzyme to aminated EC via a succinyl residue; and EC‐HMD‐GA‐CPA (IV), obtained by binding the enzyme via glutaraldehyde to a hexamethylene diamine derivative of EC. Full enzymic activity for all of the bound enzyme, such as that recorded for the immobilized CPA preparations EC‐mAb·CPA and SPA·mAb·CPA, was not detected in any of the insoluble covalently bound enzyme preparations.
Analysis and simulation of hollow‐fiber bioreactor dynamics
Authors: Kleinstreuer C. , Agarwal S. S.
Published: May 2005

A flexible and economical computer simulation model for the process analysis, parameter prediction, and optimal design of hollow‐fiber biochemical reactors (HFBRs) has been developed. The validity and predictive capability of the HFBR simulator was successfully tested with two independent laboratory case studies. Of particular interest are the transient transport and bioconversion mechanisms including the effect of radial mass convection on the substrate uptake in the lumen. The portable computer code is an efficient tool to aid in theoretical and experimental investigations. The underlying principles used for the model development are applicable to a broad family of (membrane) bioreactors.
Determination of reactor biomass by acoustic resonance densitometry
Authors: Blake‐Coleman B. C. , Clarke D. J. , Calder M. R. , Moody S. C.
Published: May 2005

Acoustic resonance densitometry (ARD) is reported as a method suitable not only for precise investigations into changes of specific gravity in bioreactor media but also as a technique able to provide an accurate wide range and direct determination of cellular mass in fermentation processes. It is further shown that this method can replace present optical procedures, minimizing dilution errors and operator involvement and is suitable for development as an on‐line biomass monitoring system.
General characteristics of optimal feed rate profiles for various fed‐batch fermentation processes
Authors: Modak J. M. , Lim H. C. , Tayeb Y. J.
Published: May 2005

General Characteristics of the optimal feed rate profiles have been deduced for various fed‐batch fermentation processes by analyzing singular controls and singular arcs. The optimal control sequences depend on the shapes of the specific growth and product formation rates, μ andπ, and the initial conditions. For fed‐batch processes described by four mass balance equations, the most general optimal control sequence consists of a period of maximum feed rate, a period of minimum feed rate (a batch period), a period of singular feed rate (variable and intermediate), and a batch period. Degenerate sequences in which one or more periods are missing can result with a particular set of initial conditions. If the fermentation time is not critical, the singular control maximizes the net yield of product and only when the time is also important, it balances a trade off between the yield of product and the specific growth rate which dictates the fermentation time. With the sequence of optimal control known, the optimal feed rate profile determination is reduced to a problem of determining switching times.