bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractOn 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

AbstractThe 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

AbstractIn 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

AbstractThe 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

AbstractPhysical 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

AbstractParticulate 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

AbstractA 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

AbstractA 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

AbstractExpression 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

AbstractThis 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

AbstractThe 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

AbstractEquilibrium 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

AbstractLiquid–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

AbstractThe 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.
Monitoring and modeling density‐dependent growth of anchorage‐dependent cells
Authors: Ruaan R.‐C. , Tsai G.‐J. , Tsao G. T. 
Published: December 2004

AbstractThe density‐dependent growth of Chinese hamster ovary (CHO) cells was monitored on‐line by using an inverted microscope. A flow system was employed for cell cultivation so that nutrient concentration could be maintained and metabolic wastes were removed. With the help of video image analysis, local cells density could be accurately calculated and cell motility and exposed cell surface area could be estimated. A computer program which accounted for change of sell size and translocation of cells was developed to stimulate dell growth. The stimulated results of the population dynamics and the variations in cell size showed good agreement with our experimental observations, Cell motility and initial cell distribution on the substratum were found to have strong effect on cell growth. © 1993 John Wiley & Sons, Inc.
Effect of carbon dioxide concentration on the bioleaching of a pyrite–arsenopyrite ore concentrate
Authors: Nagpal Soumitro , Dahlstrom Donald , Oolman Timothy 
Published: December 2004

AbstractThe effect of carbon dioxide concentration on the bacterial leaching of a pyrite‐arsenopyrite ore concentrate was studied in continuous‐flow reactors. Steady‐state operation with two feed slurry densities, 6 wt% and 16 wt% solids, were tested for the effect of carbon dioxide concentration. Bacterial growth rates were estimated via the measurement of carbon dioxide consumption rates. Aqueous‐phase carbon dioxide concentrations in excess of 10 mg/L were found to be inhibitory to bacterial growth. © 1993 John Wiley & Sons, Inc.
Air slugs entrapped cross‐flow filtration of bacterial suspensions
Authors: Lee Cheng‐Kan , Chang We‐Gwo , Ju Yi‐Hsu 
Published: December 2004

AbstractA novel cross‐flow technique for membrane filtration of bacterial cell suspensions was established. This is an air slugs entrapped cross‐flow method in which air slugs were generated by introducing air into the cross‐flow stream. As air slugs moved along with cross‐flow, the disturbance of cell sublayer formation on membrane surface was enhanced. As a consequence, filtration flux was improved and stabilized. The effect of air slugs on improving filtration flux was more pronounced in filtering gram‐negative Escherichia coli cell than grampositive Brevibacterium flavum cell. Moreover, air slug was about 50% more effective on reducing filtration resistance using ultrafiltration (UF) membrane of 300,000 molecular weight cutoff (MWCO) than microfiltration (MF) membrane of 0.2 μm. ©1993 John Wiley & Sons, Inc.
Dramatic enhancement of enzymatic activity in organic solvents by lyoprotectants
Authors: Debulis Katherine , Klibanov Alexander M. 
Published: December 2004

AbstractWhen seven different hydrolytic enzymes (four proteases and three lipases) were lyophilized from aqueous solution containing a ligand, N‐Ac‐L‐Phe‐NH2, their catalytic activity in anhydrous solvents was far greater (one to two orders of magnitude) than that of the enzymes lyophilized without the ligand. This ligand‐induced activation was expressed regardless of whether the substrate employed in organic solvents structurally resembled the ligand. Furthermore, nonligand lyoprotectants [sorbitol, other sugars, and poly(ethylene glycol)] also dramaticaliy enhanced enzymatic activity in anhydrous solvents when present in enzyme aqueous solution prior to lyophilization. The effects of the ligand and of the lyoprotectants were nonadditive, suggesting the same mechanism of action. Excipient activated and nonactivated enzymes exhibited identical activities in water. Also, addition of the excipients directly to suspensions of nonactivated enzymes in organic solvents had no appreciable effect on catalytic activity. These observations indicate that the mechanism of the excipient‐induced activation is based on the ability of the excipients to alleviate reversible denaturation of enzymes upon lyophilization. Activity enhancement induced by the excipients is displayed even after their removal by washing enzymes with anhydrous solvents. Subtilisin Carlsberg, lyophilized with sorbitol, was found to be a much more efficient practical catalyst than its “regular” counterpart. © 1993 John Wiley & Sons, Inc.