bluuebunny/crossref_metadata_2025 huggingface dataset:
In search of a thermodynamic description of biomass yields for the chemotrophic growth of microorganisms
Authors: Heijnen J. J. , Van Dijken J. P.
Published: December 2004

Correlations for the prediction of biomass yields are valuable, and many proposals based on a number of parameters (YATP, YAve, ηo, Yc, Gibbs energy efficiencies, and enthalpy efficiencies) have been published. This article critically examines the properties of the proposed parameters with respect to the general applicability to chemotrophic growth systems, a clear relation to the Second Law of Thermodynamics, the absence of intrinsic problems, and a requirement of only black box information. It appears that none of the proposed parameters satisfies all these requirements. Particularly, the various energetic efficiency parameters suffer from major intrinsic problems. However, this article will show that the Gibbs energy dissipation per amount of produced biomass (kJ/C‐mod) is a parameter which satisfies the requirements without having intrinsic problems. A simple correlation is found which provides the Gibbs energy dissipation/C‐mol biomass as a function of the nature of the C‐source (expressed as the carbon chain length and the degree of reduction). This dissipation appears to be nearly independent of the nature of the electron acceptor (e.g., O2, No3−, fermentation). Hence, a single correlation can describe a very wide range of microbial growth systems. In this respect, Gibbs energy dissipation is much more useful than heat production/C‐mol biomass, which is strongly dependent on the electron acceptor used. Evidence is presented that even a net heat‐uptake can occur in certain growth systems.

The correlation of Gibbs energy dissipation thus obtained shows that dissipation/C‐mol biomass increases for C‐sources with smaller chain length (C6 → C1), and increases for both higher and lower degrees of reduction than 4. It appears that the dissipation/C‐mol biomass can be regarded as a simple thermodynamic measure of the amount of biochemical “work” required to convert the carbon source into biomass by the proper irreversible carbon‐carbon coupling and oxidation/reduction reactions. This is supported by the good correlation between the theoretical ATP requirement for biomass formation on different C‐sources and the dissipation values (kJ/C‐mol biomass) found. The established correlation for the Gibbs energy dissipation allows the prediction of the chemotrophic biomass yield on substrate with an error of 13% in the yield range 0.01 to 0.80 C‐mol biomass/(C)‐mol substrate for aerobic/anaerobic/denitrifying growth systems.
Prediction of a protein band profile in preparative reversed‐phase gradient elution chromatography
Authors: Zoubaïr M. , Fallah El , Guiochon Georges
Published: December 2004

The overloaded band profiles of lysozyme in reversedphase preparative chromatography were recorded on a C18 chemically bonded silica column, with acetonitrile/water as the mobile phase. These experiments were carried out under isocratic conditions at 31.6, 31.9, and 32.2% acetonitrile (ACN) for loading factors up to 43% of the column saturation capacity and under linear‐solvent‐strength gradientelution with gradient slopes of 0.5 and 1% ACN/min, for loading factors up to 11.3%. The adsorption isotherms of lysozyme were measured for the same solvent compositions and found to be accurately accounted for by a bi‐Langmuir isotherm model.

With the use of a Craig model implementation of the equilibrium‐dispersive model of chromatography, the band profiles of lysozyme were calculated. An excellent agreement was observed between these calculated profiles and the experimental profiles recorded at loading factors below 5%. By contrast, band profiles calculated using a Langmuir isotherm failed to describe the experimental bands. At column loadings exceeding 8%, a slight but systematic deviation takes place between calculated and experimental profiles. It is most probably explained by the considerable concentration effect of the gradient, making the band experience phase equilibrium in a concentration range that exceeds largely the one where the isotherm data have been measured.
Effect of organic solvents on enzymatic production of cyclodextrins from unliquefied corn starch in an attrition bioreactor
Authors: Lee Yun‐Dong , Kim Hak‐Sung
Published: December 2004

Cyclodextrins were produced from unliquefied corn starch in the presence of water‐miscible organic solvents using cyclodextrin glycosyltransferase (CGTase) in an attrition bioreactor. The production yield was singnificatly increased by isopropanol and tertiary butanol, and maximum enhancement was observed to be about 40% by 5% tertiary butnol. Increase in the production of cyclodextrins by organic solvents seems to be due to the fact that organic solvents decreased the product inhibition of CGTase by forming an inclusion complex with cyclodextrins.
Hydrolysis of butteroil by immobilized lipase using a hollow‐fiber reactor: Part III. Multiresponse kinetic studies
Authors: Malcata F. Xavier , Hill Charles G. , Amundson Clyde H.
Published: December 2004

A lipase from Aspergillus niger immobilized by adsorption on microporous, polypropylene hollow fibers was used to effect the continuous hydrolysis of the glycerides of butter oil at 40°C and pH 7.0. The effluent concentrations of 10 different free fatty acid products were measured by highperformancee liquid chromatography (HPLC). Multiresponse nonlinear regression methods were used to fit the data to a multisubstrate rate expression derived from a Ping Pong Bi Bi mechanism in which the rate‐controlling step is deacylation of the lipase. Thermal deactivation of the enzyme was also included in the mathematical model of reactor performance. A postulated normal distribution of vmax with respect to the chain length of the fatty acid (with an additive correction for the degree of unsaturation) was tested for statistical significance. The model is useful for predicting the free fatty acid profile of the lipolyzed butteroil product over a wide range of flow rates.
Hydrolysis of butteroil by immobilized lipase using a hollow‐fiber reactor: IV. Effects of temperature
Authors: Malcata F. Xavier , Hill Charles G. , Amundson Clyde H.
Published: December 2004

A lipase from Aspergillus niger, immobilized by adsorption on microporous polypropylene hollow fibers, was used to effect the hydrolysis of the glycerides of melted butterfat at pH. 7.0 at 40, 50, 55, and 60°C. Mcllvane buffer was pumped upward through the lumen, and melted butterfat was pumped upward through the shell side of a hollow fiber reactor. Nonlinear regression methods were employed to determine the kinetic parameters of models based on combinations of three nested rate expressions for the hydrolysis reaction with three nested rate expressions for thermal deactivation of the enzyme. A rate expression containing four lumped parameters is sufficient to model the release of free fatty acids as a function of reactor space time and time elapsed after immobilization. Nonlinear regression methods were also employed in global fits of the data to rate expressions containing an explicit dependence on temperature. For the reaction conditions used in this research, a 14‐parameter rate expression is necessary to accurately model the overall release of free fatty acids as a continuous function of the absolute temperature, initial substrate concentrations, reactor space time, and time elapsed after immobilization of the lipase.
On‐line fluorescence‐monitoring of the methanogenic fermentation
Authors: Peck Michael W. , Chynoweth David P.
Published: December 2004

On‐line in situ fluorescence measurements of the methanogenic fermentation were conducted with reactors receiving either glucose or a mixture of volatile fatty acids as the substrate. The reactors were perturbed from steady‐state conditions in order to assess the response of fluorescencemonitoring probes. Two fluorescence‐monitoring probes were evaluated over a period of 8 months; they performed in a consistent manner, and their response was not significantly affected by the changes in pH and redox potential encountered during routine reactor operation. A commercially available probe, designed to measure NAD(P)H, demonstrated particular promise for detecting imbalance caused by the entry of air, inhibitor addition and was capable of distinguishing between different substrates. This fluorescence‐monitoring probe detected imbalance more rapidly than other on‐line measurements such as pH, Eh, or gas production, or off‐line measurements such as volatile fatty acid concentration or gas composition. An experimental fluorescence‐monitoring probe, designed to measure coenzyme F420, also showed some promise in this regard. The response of the fluorescence‐monitoring probes also revealed details of the metabolic routes in the reactors and the probes represent a useful research tool. For example, a failure to observe the characteristic response of the NAD(P)H‐monitoring probe to formate addition during the metabolism of acetate, propionate, or glucose strongly suggests that any formate liberated during their catabolism is degraded via a different route to exogenously added formate.
The effects of surface adsorption on the thermal stability of proteins
Authors: Steadman Bryan L. , Thompson Karen C. , Middaugh C. Russell , Matsuno Ken , Vrona Susan , Lawson Erlinda Q. , Lewis Randolph V.
Published: December 2004

The effect of surface adsorption on the structure and stability of proteins is a matter of increasing interest in biotechnology. Therefore, we have examined the effect of adsorption to silica on the thermal stability of 7 proteins employing differential scanning calorimetry (DSC) and front surface fluorescence (FSF) spectroscopy. In general, it was found that surface adsorption decreased the thermal stability of the bound protein. Using lysozyme for further studies, DSC, FSF, and FTIR spectroscopies, as well as enzymatic activity measurements, were used to explore the effect of decreasing surface apolarity on stability. It was observed that increasing surface apolarity produced decreasing stability and increasing structural alteration of the adsorbed protein.
Biosurfactants and aqueous two‐phase fermentation
Authors: Drouin C. M. , Cooper D. G.
Published: December 2004

The partition of surfactants and a biosurfactant‐producing microorganism was studied in polyethylene glycol and dextran aqueous two‐phase systems. In the presence of sodium phosphate, surfactants distributed themselves according to charge. Cationic surfactants preferred the bottom phase, while anionic surfactants were attracted to the top phase. Incresing the phosphate molarity or the pH resulted in a more 1‐sided surfactant partitioning. Biosurfactant partitioning was weaker than synthetic surfactant partitioning due to the weaker effective charge and lack to strong specific affinity for any of the phase‐forming polymers. Bacillus Subtilis cells partitioned very storngly to the bottom phase. The bioscurfactant, surfactin, produced by this microorganism partitioned to the top phase. Batch fermentations were carried out in an aqueous 2‐phase system. Surfactin was produced in larger quanities in the 2‐phase fermentation than in the regular mineral salts medium.
Batch cultivation of Methylosinus trichosporium OB3b: II. Production of particulate methane monooxygenase
Authors: Park Sunghoon , Shah Nilesh N. , Taylor Robert T. , Droege Michael W.
Published: December 2004

The obligatory methanotroph, Methylosinus trichosporium OB3b, was studied to optimize the batch culture conditions for the formation of particulate methane monooxygenase (pMMO) in a nitrate minimal salts medium. The important medium components investigated were copper, carbon dioxide, and nitrate. The whole‐cell specific pMMO activity decreased sharply with increasing copper concentrations in the range of 10–40 μM and remained constant upon further increases of the copper concentration to 120 μM. The cell growth rate (μ), on the other hand, decreased over the entire range (10–120 μM) of copper concentrations tested. When pMMO was produced in a bioreactor with an optimal initial copper concentration of 10 μM, M. trichosporium OB3b exhibited a much faster overall growth rate and a higher whole‐cell propene epoxidation activity compared to our earlier study, in which soluble methane monooxygenase (sMMO) was produced with copper‐deficient medium. The addition of external carbon dioxide to the bioreactor culture eliminated an initial lag period in the cell growth. When the standard culture medium nitrate concentration (10 mM) was depleted, the pMMO activity, but not the growth rate, decreased rapidly. The whole‐cell specific pMMO activity could be maintained by subsequent supplementation of nitrate. A 4‐fold higher initial culture medium nitrate concentration of 40 mM, however, resulted in slower cell growth and lower pMMO activity. These observations demonstrate that, in addition to affecting the exclusive production of pMMO, copper also has an important previously unrecognized role in enhancing the growth rate of M. trichosporium OB3b. They also indicate that for the optimal batch production of pMMO with the minimal medium under study, nitrate should be supplied intermittently during the course of cultivation until other culture medium components become growth‐limiting.
Modeling particle transport by bubbles for performance guidelines in airlift fermentors
Authors: Snape J. B. , Thomas N. H.
Published: December 2004

A calculation method has been developed to model the statistical transport of biological particles in bubble‐driven flows, with special reference to the biokinetics of environmental excursions experienced by individual cells, aggregated cells, or immobilization beads in airlift bioreactors. Interim developments on modeling the transport of such particles in concentric tube devices are reported. The calculation is driven by user‐prescribed global parameters for the bioreactor geometry, bulk air flow rate, and particle parameters (size and slip speed). The algorithm calls on empirical data correlations for void fraction, bulk liquid flow rate, and bubble sizes and slip speeds, optimally selected from a large bibliographic database. The Monte Carlo algorithm concentrates on simulating particle transport in the bubbly riser flows.

The packaged family of correlations and calculations represents, in effect, an expert system augmented by a transport simulation suited to characterizing the biokinetic response of cells cultured in airlift bioreactors.
Development of a multienzyme reactor for dopamine synthesis: II. Reactor engineering and simulation
Authors: Anderson William A. , Moo‐Young Murray , Legge Raymond L.
Published: December 2004

Aspects of reaction engineering associated with multienzyme reactions have been studied in a system where dopamine is produced from catechol, pyruvate and ammonium by sequential enzymatic reactions catalyzed by tyrosine phenol lyase (TPL) and tyrosine decarboxylase (TDC). Microbial cells containing TPL activity (Erwinia herbicola) and TDC activity (Streptococcus faecalis) were coimmobilized in glutaraldehyde cross‐linked porcine gelatin beads with a mean diameter of 2.8 mm for use in the reactions. Measurement of the transport properties in the beads indicate that the gelatin matrix does not significantly increase the diffusion resistance and that dopamine partitions into the matrix (K = 2). A packed‐bed reactor containing the coimmobilized cell beads successfully produced dopamine, although with a low conversion. Using computer simultaneous it is shown that separate, sequential TPL and TDC, rather than simultaneous, reactions, would require smaller reactors overall for the same conversion. © 1992 John Wiley & Sons, Inc.
Studies on the isolation of penicillin acylase from Escherichia coli by aqueous two‐phase partitioning
Authors: Guan Yue , Wu Xing‐Yan , Treffry Timothy E. , Lilley Terence H.
Published: December 2004

A method of enzyme release and aqueous two‐phase extraction is described for the separation of penicillin acylase from Escherichia coli cells. Butyl acetate, 12% (v/v), treatment combined with freeze–thawing gives up to 70% enzyme release. For polyethylene glycol (PEG) + phosphate two‐phase extraction systems the enzyme purity and yield were rather low. Modified PEG, including PEG–ampicillin, PEG–aniline, PEG–phosphate, and PEG–trimethylamine, were synthesized and used in aqueous two‐phase systems; PEG–trimethylamine is the most satisfactory. A system containing 12% (w/w) PEG4000, 8% (w/w) of which is PEG–trimethylamine, with 0.7M potasium phosphate at pH 7.2, resulted in the enzyme selective partition being greatly enhanced by charge directed effects. Possible mechanisms for the separation process are discussed. © 1992 John Wiley & Sons, Inc.
A structured dynamic model for the baculovirus infection process in insect‐cell reactor configurations
Authors: De Gooijer Cornelis D. , Koken Rick H. M. , Van Lier Frank L. J. , Kool Marcel , Vlak Just M. , Tramper Johannes
Published: December 2004

A mathematical description of the infection of insect cells with baculovirus in a continuously operated reactor configuration is presented. The reactor configuration consists of one bioreactor in which insect cells (Spodoptera frugiperda) are grown followed by one or two bioreactors in which cells are infected by a baculovirs (Autographa californica nuclear polyhedrosis virus). It was demonstrated that the so‐called passage effect is responsible for the observed difference in run time between a configuration with one or with two infection vessels. Furthermore, a model is presented based on the hypothesis that the limited run time of series of continuously operated bioreactors is associated with the occurrence of a virus particle (so‐called virion) that is defective and has interfering properties. With the assumption that not all nonoccluded virions are capable of establishing a correct infection leading to new virus production, infection levels in continuously operated reactor configurations could be described well with the model. © 1992 John Wiley & Sons, Inc.
Treatment of metal‐contaminated water using bacterial sulfate reduction: Results from pilot‐scale reactors
Authors: Dvorak Darryl H. , Hedin Robert S. , Edenborn Harry M. , McIntire Pamela E.
Published: December 2004

Simple anaerobic reactors were installed to treat metal‐contaminated water in an underground coal mine and at a smelting residues dump in Pennsylvania. The reactors consisted of barrels and tanks filled with spent mushroom compost, within which bacterial sulfate reduction became established. Concentrations of Al, Cd, Fe, Mn, Ni, and Zn were typically lowered by over 95% as contaminated water flowed through the reactors. Cadmium, Fe, Ni, and some Zn were retained as insoluble metal sulfides following their reaction with bacterially generated H2S. Aluminum, Mn, and some Zn hydrolyzed and were retained as insoluble hydroxides or carbonates. Reactor effluents were typically circumneutral in pH and contained net alkalinity. The principal sources of alkalinity in the reactors were bacterial sulfate reduction and limestone dissolution. This article examines the chemistry of the reactor systems and the opportunities for enhancing their metal‐retaining and alkalinity‐generating potential. © 1992 John Wiley & Sons, Inc.
Analysis of noise and bias in fermentation oxygen uptake rate data
Authors: Royce Patrick N. , Thornhill Nina F.
Published: December 2004

The calculation of many derived fermentation variables such as the respiratory quotient (RQ) and mass transfer coefficient (KLa) requires the differences between the molar percentages of oxygen and carbon dioxide in the fermentor inlet and exit gas, called the %OUR and %CER. Noise and bias in %CER data is of order that in the exit gas carbon dioxide analysis. However, the relative amount of noise in the %OUR is one to two orders of magnitude greater than the noise in the raw oxygen analyses because the %OUR is calculated as a small difference between two large quantities. The noise in the %OUR is white with a Gaussian amplitude probability distribution of absolute standard deviation 0.0145. A chi‐square filter of the %OUR data is shown to considerably improve the quality of the calculated RQ and KLa for a fermentation of Streptomyces clavuligerus. © 1992 John Wiley & Sons, Inc.
Overexpression of cloned genes using recombinant Escherichia coli regulated by a T7 promoter: I. Batch cultures and kinetic modeling
Authors: Miao Fudu , Kompala Dhinakar S.
Published: December 2004

A novel Eschericha coli expression system directed by bacteriophage T7 RNA Polymerase utilized for overexpression of the cloned gene. The recombinant cell contains the plasmid with a bacteriophage promoter, the T7 promoter, to regulate the expression of the target gene. This promoter is recongnized only by T7 RNA polymerase, whose gene has been fused into the host chromosome and is under control of the lacUV5 promoter. Therefore, the target gene on the plasmid can be expressed only in the presence of T7 RNA polymerase, which is induced by isopropyl‐β‐D‐thiogalactopyranoside (IPTG). The batch cultures were performed to investigate the effect of induction on kinetics of cell growth and foreign protein formation and to determine the optimal induction strategy. It was observed that the specific growth rates of the recombinant cells dramatically decrease after induction, and that there is an optimal induction time for maximizing the accumulated intracellular foreign protein. This optimal induction time varies singificantly with inducer concentration. To better understand the optimal behavior, a lumped mechanistic model was constructed to analyze the induced cell growth and foreign protein formation rates. © 1992 John Wiley & Sons, Inc.
A structured model for simulation of cultures of the cyanobacterium Spirulina platensis in photobioreactors: II. Identification of kinetic parameters under light and mineral limitations
Authors: Cornet J. F. , Dussap C. G. , Cluzel P. , Dubertret G.
Published: December 2004

A structured model for the culture of cyanobacteria in photobioreactors is developed on the basis of Schuster's approximations for radiative light transfer. This model is therefore limited to monodimensional geometries and kinetic aspects.

Light‐harvesting pigments play a crucial role in defining the profile of radiative transfer inside the culture medium and in controlling the metabolism, particularly the metabolic deviations induced by mineral limitations. Modeling therefore requires the biomass to be divided into several compartments, among which the light‐harvesting compartment allows a working illuminated volume to be defined within the photobioreactor. This volume may change during batch cultures, largely decreasing as pigment concentration increases during growth but increasing as pigments are consumed during mineral limitation. This approach enables, in photobioreactors of simple parallelepipedic, geometries, kinetic parameters to be determined with high accuracy; this may then be extended to vessels of more complex geometries, such as cylindrical photobioreactors.

The model is applied to controlled batch cultures of the cyanobacterium Spirulina platensis in parallelepipedic photobioreactors to assess its ability to predict the behavior of these microorganisms in conditions of light and mineral limitations. Results allowed the study of optimal operating condition for continuous cultures to be approached © 1992 John Wiley & Sons, Inc.
Effective extracellular production of Bacillus stearothermophilus esterase by pH‐stat modal fed‐batch culture of recombinant Bacillus brevis
Authors: Tulin Edgardo E. , Ueda Shunsaku , Yamagata Hideo , Udaka Shigezo , Yamane Tsuneo
Published: December 2004

An automated two‐component substrate feeding strategy with a pH‐stat modal fed‐batch culture using a high pH limit was developed to effectively porduce esterase from a hyperprotein exreting Bacillus brevis HPD31 harboring a plasmid pHSC131 which carries a Bacillus stearothermo philus esterase gene. First, the effect of single‐ and multi‐substrate feedings on the growth and activity of the excreted esterase was investigated. Then a two‐component (polypepton + glucose) feeding using different feed rates was studied. Highest activity of the excreted esterase (34 U/mL) was obtained when the concentrations of poly‐pepton and glucose in the nutrient feed solution were 250 and 41.60 g/L respectively. The absence and excessive amount of glucose in the nutrient feed solution was ineffective for the exracellular esterase formation because without glucose the increase in cell concentration was minimum while excessive amount of glucose favored cell growth at the expense of the esterase production. It is believed that the mechanism of enzyme excretion is growth dependent and that a higher cell growth of the host is in effect unfavorable for the enzyme production. The feed rate, automatically controlled by the direct signal of the pH change, at 0.30 mL/pulse was found optimum for the esterase production while lower (0.15 mL/pulse) and higher (0.67 mL/pulse) feed rates did not produce good results. The activity of the excreted esterase was increased more than eight times from 4 U/mL obtained in the conventional batch culture to 34 U/mL obtained in this study. The esterase productivity was likewise increased more than threefold. © 1992 John Wiley & Sons, Inc.
Advanced control of glutathione fermentation process
Authors: Sakato Kuniaki , Tanaka Hisao
Published: December 2004

A study was performed to understand the fermentation process for production of glutathione fermentation (GSH) with an improved strain of baker's yeast. Simultaneous utilization of sugar and ethanol has been found to be a key factor in the industrial process to produce GSH using Saccharomyces cerevisiae KY6186. Based on this observation, the optimal sugar feed profile for the fed‐batch operation has been determined. A feedforward/feedback control system was developed to regulate the sugar feed rate so as to maximize GSH production yields. Using the feedforward/feedback control system and the on‐line data of oxygen and ethanol concentration in exhaust gas, the successful scaleup to the production level was accomplished. An average of 40% improvement of glutathione production compared to a conventionally programmed control of exponential fed‐batch operation was found in the new process. © 1992 John Wiley & Sons, Inc.
Activation of microcarrier‐attached lymphocytes in microgravity
Authors: Bechler B. , Cogoli A. , Cogoli‐Greuter M. , Müller O. , Hunzinger E. , Criswell S. B.
Published: December 2004

A technology has been developed to achieve optimal attachment of adhesion‐independent lymphocytes to microcarrier beads. The activation of T‐lymphocytes by concanavalin A was tested under microgravity conditions in an experiment carried out in space during the first Spacelab Life Science Mission. Activation, measured as the synthesis of deoxyribonucleic acid (DNA) and the production of interferon‐gamma, more than doubled in attached lymphocytes in microgravity. The depression of the activation discovered in previous space experiments is due to an impairment not of the lymphocyte but of the macrophage function. The system described here may be useful for radiobiological investigations on the effect of high‐energy particles and for testing the efficiency of the immune system in humans during the long‐duration space flight planned in the future. The biotechnological significance of the increased lymphokine production in space remains to be assessed. © 1992 John Wiley & Sons, Inc.
Fragmentation of cellulose by the major Thermomonospora fusca cellulases, Trichoderma reesei CBHI, and their mixtures
Authors: Walker L. P. , Wilson D. B. , Irvin D. C. , McQuire C. , Price M.
Published: December 2004

In this study, the fragmentation activities of Thermomonospora fusca cellulases E2, E3, E5, Trichoderma reesei CBHI, and their mixtures were measured to study synergism in fragmentation. Fragmentation studies revealed that only two pure cellulases, T. fusca E2 and E5 had significant fragmentation activity. T. fusca E3 shows strong synergism in fragmentation both in the production of reducing sugars and in fragmentation with both T. fusca endoglucananses and with T. reesei CBHI. Most mixtures containing CBHI produced higher rates of fragmentation than comparable mixtures containing E3. The highest rate and extent of reducing sugar formation and the highest fragmentation activity were obtained with a mixture of E2, E3, and CBHI. © 1992 John Wiley & Sons, Inc.
A black box mathematical model to calculate auto‐ and heterotrophic biomass yields based on Gibbs energy dissipation
Authors: Hoijnen J. J. , van Loosdrecht M. C. M. , Tijhuis L.
Published: December 2004

On the basis of the estimated Gibbs energy dissipation per C‐mil biomass produced and a convenient black box description of microbial growth, a general equation for the calculation of the yield of biomass on electron donor has been obtained. This black box model defines four formal electron donating reactions for biomass, carbon source, electron donor, and electron acceptor. The proposed description leads to a simple equation which gives the biomass yield on electron donor for chemotrophic growth systems under carbon and energy limitation for which biomass is the only anabolic product. The variables involved are the degrees of reduction and the Gibbs energy characteristics of the four compounds, and the required Gibbs energy dissipation per C‐mol produced of biomass. It appears that biomass yields on electron donor for auto‐ and heterotrophic growth under aerobic, denitrifying, and fermentative conditions can be estimated with 10–15% error in a range of YDX‐values of 0.01–0.80 C‐mol/(C)‐mol electron donor. Also, simple regularities in the Gibbs energy and enthalpy of organic substrates are found. Furthermore, simple relations are derived to calculate the thermodynamic maximal biomass yield, conditions required for growth to occur, heat production, biomass yield on electron acceptor, and anaerobic product yield. Finally a new definition of thermodynamic efficiency is derived. © 1992 John Wiley & Sons, Inc.
Some characteristics of protein precipitation by salts
Authors: Shih Ying‐Chou , Prausnitz John M. , Blanch Harvey W.
Published: December 2004

The solubilities of lysozyme, α‐chymotrypsin and bovine serum albumin (BSA) were studied in aqueous electrolyte solution as a function of ionic strength, pH, the chemical nature of salt, and initial protein concentration. Compositions were measured for both the supernatant phase and the precipitate phase at 25°C. Salts studied were sodium chloride, sodium sulfate, and sodium phosphate. For lysozyme, protein concentrations in supernatant and precipitate phases are independent of the initial protein concentration; solubility can be represented by the Cohn salting‐out equation. Lysozyme has a minimum solubility around pH 10, close to its isoelectric point (pH 10.5). The effectiveness of the three salts studied for precipitation were in the sequence sulfate > phosphate > chloride, consistent with the Hofmeister series. However, for α‐chymotrypsin and BSA, initial protein concentration affects the apparent equillibrium solubility. For these proteins, experimental results show that the compositions of the precipitate phase are also affected by the initial protein concentration. We define a distribution coefficient κe to represent the equilibrium ratio of the protein concentration in the supernatant phase to that in the precipitate phase. When the salt concentration is constant, the results show that, for lysozyme, the protein concentrations in both phases are independent of the initial protein concentrations, and thus κe is a constant. For α‐chymotrypsin and BSA, their concentrations in both phases are nearly proportional to the initial protein concentrations, and therefore, for each protein, at constant salt concentration, the distribution coefficient κe is independent of the initial protein concentration. However, for both lysozyme and α‐chymotrypsin, the distribution coefficient falls with increasing salt concentration. These results indicate that care must be used in the definition of solubility. Solubility is appropriate when the precipitate phase is pure, but when it is not, the distribution coefficient better describes the phase behavior. © 1992 John Wiley & Sons, Inc.
Distribution of immobilized enzymes on porous membranes
Authors: Dalvie Sandeep K. , Baltus Ruth E.
Published: December 2004

In this article, the results from a theoretical and experimental investigation of enzyme immobilization in porous membranes are reported. A theoretical model of the immobilization process, which accounts for restricted diffusion of enzyme in the pores of the membrane, has been developed. The model predicts the effect of immobilization kinetics and time of immobilization on the enzyme distribution in the pores of the membrane. The immobilization of glucose oxidase and glucose oxidase–biotin conjugate on porous alumina membranes was experimentally investigated. Enzyme uptake data was correlated to the theory to determine the rate constant of imobilization and the distribution of the enzyme in the pore. Immobilization studies were carried out for enzyme adsorption and for enzyme attachment by covalent coupling. The distribution of enzyme was experimentally studied by assembling five membranes in the diffusion cell. Following immobilization, the membranes were separated and each was assayed for activity. The amount of active enzyme present in each membrane yielded a discrete distribution that compared well with that predicted by theory. © 1992 John Wiley & Sons, Inc.
Effects of heat shock on the production of human erythropoietin from recombinant CHO cells
Authors: Tsao Eric I. , Bohn Martie A. , Omstead Daniel R. , Munster Michael J. , Numsuwan Vanchai
Published: December 2004

The production of recombinant proteins by mammalian cells demands a highly controlled environment for cell cultivation. Temperature stress represents a commonly encountered disturbance in both research and process environments. In this study, we examined the effects of heat shock on the expression of recombinant human erythropoietin (EPO) in a Chinese hamster ovary (CHO) cell line. Biosynthetic radiolabeling experiments indicated that the cells exposed to a 42°C/1‐hour heat shock exhibit a transient reprogramming of transcription and translation characterized by the inhibition of protein synthesis and induction of heat shock proteins. The rate of protein synthesis decreased by 50% after the heat shock, while the rate of RNA synthesis increased by 50% initially and then quickly reduced to 80% of the control level. The protein and RNA synthesis rates were fully recovered in approximately 48 hours after the heat shock. However, we found that the expression of EPO was not arrested by the heat shock. The glycosylation patterns, as examined by isoelectric focusing, of either the culture supernatant or the purified EPO were not affected by the heat shock. In contrast, a 45°C/1‐hour heat shock terminated RNA and protein synthesis immediately and caused culture death in 12 hours. Cellular responses to temperature stress were affected by the metabolic state of the cells; cells maintained in serum‐free medium were more sensitive than cells growing exponentially in the presence of serum. We have also examined the kinetics of metabolic responses of the cells to heat shock with respect to nutrient uptake and metabolite accumulation. © 1992 John Wiley & Sons, Inc.
Rheological characteristics of cell suspension and cell culture of Perilla frutescens
Authors: Zhong Jian‐Jiang , Seki Tatsuji , Kinoshita Shin‐Ichi , Yoshida Toshiomi
Published: December 2004

Physical properties such as viscosity, fluid dynamic behavior of cell suspension, and size distribution of cell aggregates of a plant, Perilla frustescens, cultured in a liquid medium were studied. As a result of investigations using cells harvester after 12 days of cultivation in a flask, it was found that the apparent viscosity of the cell suspension did not change with any variation of cell concentration below 5 g dry cell/L but markedly increased when the cell concentration increased over 12.8 g dry cell/L. The cell suspension exhibited the characteristics of a Bingham plastic fluid with a small yield stres. The size of cell aggregates in the range 74 to 500 μm did not influence the rheological characteristics of the cell suspension. The rheological characteristics of cultivation mixtures of P. frutescens cultivated in a flask and in a bioreactor were also investigated. The results showed that the flow characteristics of the cell culture could be described by a Bingham plastic model. At the later stage of cultivation, the apparent viscosity increased steadily, even though the biomass concentration (by dry weight) decreased, due to the increase of individual cell size. © 1992 John Wiley & Sons, Inc.
Protein immobilization to alumina supports: II. Papain immobilization to alumina via organophosphate linkers
Authors: Hyndman David , Burrell Robert , Lever Gordon , Flynn T. Geoffrey
Published: December 2004

Particulate aluminum oxides (alumina) were examined as supports for the immobilization of the proteolytic enzyme papain. Two alumina supports termed C1 and CPC were derivatized using organic phosphate linkers to create free carboxyl groups using a two‐step process. Papain binding to these derivatized aluminas was performed using the water soluble carbodiimide 1‐ethyl‐3‐(dimethylaminopropyl) carbodiimide. Reactions were optimal at 10 mM carbodiimide. The immobilized protein showed similar kinetic constants when compared to the solution protein. The pH dependence and thermal stability were essentially identical. The immobilized papain showed a blue shift in the intrinsic fluorescence emission maxima. Papain modified with the active site‐specific fluorescent probe acrylodan showed overlapping emission maxima. These results are interpreted as retention of the hydrophobic environment of the active site with a perturbation in the structure of the rest of the protein caused by its association with the negatively charged surface. © 1992 John Wiley & Sons, Inc.
Model analysis of biological oxygen transfer enhancement in surface‐aerated bioreactors
Authors: Ju Lu‐Kwang , Sundarajan Anand
Published: December 2004

A model was developed to evaluate the effects of cells and surfactants on oxygen transfer in surface‐aerated bioreactors. The model assumed the presence of serial layers of adsorbed surfactants and microorganisms directly adjacent to the gas–liquid interface due to their surface activities, followed by a stagnant liquid layer to account for the oxygen transfer resistance in the liquid phase. The interfacial surfactant film, although posing as an additional resistance, was found to have negligible effect on the oxygen transfer rate because of its extremely small thickness as compared to the cell monolayer and the stagnant liquid layer. On the other hand, cells affect oxygen transfer by two mechanisms: the biological enhancement due to the respiration of interfacial cells and the physical blocking resulting from the semipermeable nature of cell bodies. Due to the low specific oxygen uptake rates of the sludges, the two mechanisms were found to be of comparable importance in activated‐sludge systems; the oxygen transfer enhancement factor, E, varied from about 0.97 to 1.10 depending on the operating conditions. The biological enhancement effect, however, predominated in fermentations of actively growing bacteria. At relatively low agitation speed (e. g., 300 rpm), the value of E could reach about 3 to 5 in fermentations with high cell concentrations. Effects of other operating variables, such as the agitation intensity, the oxygen content in the mixed liquor, and the bulk cell concentration, on biological oxygen transfer enhancement were also studied. © 1992 John Wiley & Sons, Inc.
A novel bioreactor for the biodegradation of inhibitory aromatic solvents: Experimental results and mathematical analysis
Authors: Choi Yong‐Bok , Lee Jang‐Young , Kim Hak‐Sung
Published: December 2004

A novel bioreactor for the biodegradation of toxic aromatic solvents, such as benzene, toluene, and xylenes in liquid effluent stream, was developed. Silicon tubing was immersed in the completely mixed and aerated bioreactor, and liquid toluene as a model solvent was circulated within the tubing. Toluene diffused out of the tube wall and was transferred at high rate into the culture broth, where biodegradation occurred. The effect of operating parameters on the toluene transfer rate was investigated. During continuous operation, the biodegradation rate was considerably higher than those obtained using conventional methods. A mathematical model was established for continuous biodegradation, and simulation results coincided with the experimental results. The performance and operational criteria of the bioreactor were analyzed on the basis of both the experimental and simulation results. © 1992 John Wiley & Sons, Inc.
Isolation, renaturation, and formation of disulfide bonds of eukaryotic proteins expressed in Escherichia coli as inclusion bodies
Authors: Fischer Bernhard , Sumner Ian , Goodenough Peter
Published: December 2004

Expression of recombinant proteins in Escherichia coli often results in the formation of insoluble inclusion bodies, In case of expression of eukaryotic proteins containing cysteine, which may form disulfide bonds in the native active protein, often nonnative inter‐ and intramolecular disulfide bonds exist in the inclusion bodies. Hence, several methods have been developed to isolate recombinant eukaryotic polypeptides from inclusion bodies, and to generate native disulfide bonds, to get active proteins. This article summarizes the different steps and methods of isolation and renaturation of eukaryotic proteins containing disulfide bonds, which have been expressed in E. coli as inclusion bodies, and shows which methods originally developed for studying the folding mechanism of naturally occurring proteins have been successfully adapted for reactivation of recombinant eukaryotic proteins. © 1993 John Wiley & Sons, Inc.
Classification of plant somatic embryos by computer vision
Authors: Hämäläinen Jari J. , Kurtén Ulrika , Kauppinen Veli
Published: December 2004

This article deals with the automation of the process of somatic embryogenesis for the propagation of plants. An important problem is the monitoring of the embryo production process in order to decide the time to start harvesting embryos for further processing. The classification algorithm development for somatic embryos of birch (Betula pendula Roth) showed that automated recognition of embryos at different developmental stages is possible. No globular stage embryos were classified to be heart or torpedo stage and no heart or torpedo stage embryos were classified to be at globular stage. Heart and torpedo stage embryos were classified into three developmental classes by a new index that describes the relation of embryo breadth to the length of the root. The probability of classifying a nonembryo as an embryo was less than 1%, and 14% of the object classified as embryos by a human expert were discarded by the algorithm. A computer vision system suitable for automated monitoring of samples from the bioreactor was constructed. © 1993 John Wiley & Sons, Inc.
Immobilized catalase: Deactivation and reactor stability
Authors: Vasudeven P. T. , Weiland R. H.
Published: December 2004

The quasi‐steady behavior of a continuous flow reactor in which hydrogen peroxide is decomposed by immobilized catalase is investigated. Under certain conditions, reactors involving such substrate‐inhibited, self‐poisoning reactions are susceptible to suddne failure and the reactor moves catastrophically from high‐ to low‐conversion quasi‐steady states. This exchange‐of‐steady‐states phenomenon is ex‐amined in the light of experimental evidence for the enzyme catalase from bovine liver. © 1993 John Wiley & Sons, Inc.
Adsorption of BSA on QAE‐dextran: Equilibria
Authors: Yoshida Hiroyuki , Nishihara Hideki , Kataoka Takeshi
Published: December 2004

Equilibrium isotherms for adsorption of bovine serum albumin (BSA) on a strong‐base (QAE) dextran‐type ion exchanger have been determined experimentally. They were not affected by the initial concentration of BSA but were affected by pH considerably. They were correlated by the Langmuir equation when pH ≥ 5.05 and by the Freundlich equation of pH 4.8, which is close to pl ≃ 4.8 of BSA. The contribution of ion exchange to adsorption of BSA on the ion exchanger was determined experimentally. The maximum amounts of inorganic anion exchanged for BSA were 1% and 0.4% of the exchange capacity of the ion exchanger at pH 6.9, respectively. Since the effect of the ion exchange on the adsorption appeared small, BSA may be adsorbed mainly by electrostatic attraction when pH ≥ 5.05 and by hydrophobic interaction or hydrogen bonding at pH 4.8. When NaCl coexisted in the solution, the shape of the isotherm was similar to the Langmuir isotherm, but it is shifted to the right. When the concentration of NaCl was 0.2 mol/dm3, BsA was not adsorbed on the resin. When BSA was dissolved in pure water, the saturation capacity of BSA on HPO42−,‐orm resin was about 2 times larger than that for adsorption from the solution with buffer (pH 6.9 and 8.79). The saturation capacity for adsorption of BSA in pure water on HPO42− + H2O4−‐from resin was much smaller than that from the solution with buffer. The isotherms for univalent Cl−‐and H2PO4−‐form resin was peculiar; that is, the amount of BSA adsorbed decreased with increasing the liquid‐phase equilibrium concentration of BSA. © 1993 John Wiley & Sons, Inc.
Industrial separation of carboxylic and amino acids by liquid membranes: Applicability, process considerations, and potential advantage
Authors: Eyal Aharon M. , Bressler Eyal
Published: December 2004

Liquid–liquid extraction and membrane separation are well‐known separation method of extensive industrial application. Their incorporation into liquid membranes has the potential of several advantages, some of which are of particular interest for the recovery of carboxylic and amino acids: selectivities higher than those attainable by current separation methods, saving on energy costs for final concentration of separated products, high fluxes, compact installation, and low capital and operation costs. Stability of the liquid advantages, can be secured by utilizing extractant blocking polymeric membranes, Applicability, process consideration, and economic implications for recovery for carboxylic and amino acids by various extractant/membrane combinations are discussed. © 1993 John Wiley & Sons, Inc.
Plasmid burden in chemostat culture of Escherichia coli: Its effect on the selection for overproducers of host enzymes
Authors: Kyslik P. , Dobisova M. , Maresova H. , Sobotkova L.
Published: December 2004

The effect of plasmid‐mediated metabolic burden of on the expression of the host genes and its consequences on the plasmid maintenance were studied in carbon‐limited chemostat culture of Escherichia coli 1EA(pBR322) subject to selection for strains overproducing chromosomally coded ribitol dehydrogenase. The chemostat population became rapidly heterogeneous and the competition among evolved strains was found to be crucial for the kinetics of the plasmid loss from the culture. The selective disadvantages in growth rate associated with plasmid carriage in the parent‐like and ribitol dehydrogenase‐overproducing strains was estimated. © 1993 John Wiley & Sons, Inc.