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  • Inorganic Chemistry  (727)
  • Biochemistry and Biotechnology  (641)
  • 1990-1994  (1,368)
  • 1950-1954
  • 1930-1934
  • 1993  (1,368)
Collection
Keywords
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  • 1990-1994  (1,368)
  • 1950-1954
  • 1930-1934
Year
  • 1
    Electronic Resource
    Electronic Resource
    Isolation, renaturation, and formation of disulfide bonds of eukaryotic proteins expressed in Escherichia coli as inclusion bodies (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 3-13 
    Details
    ISSN: 0006-3592
    Keywords: recombinant protein ; Escherichia coli ; inclusion body ; renaturation ; disulfide bond ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410103
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  • 2
    Electronic Resource
    Electronic Resource
    Evolutionary operation (EVOP) to optimize three-dimensional biological experiments (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 67-71 
    Details
    ISSN: 0006-3592
    Keywords: optimization ; EVOP ; inducer ; protease ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Evolutionary operation (EVOP) is used as an efficient technique for optimization of three variable experimental parameters using two-level factorial designs with center points. For metabolic function like enzyme synthesis by microorganisms, small amounts of metal ions, surfactants, and vitamins act as inducers. The desired quantities of these chemicals are, however, species dependent and have to be found out or each microorganism. By employing the EVOP technique, the requirements of these chemicals have been optimized for the production of protease by Rhizopus oryzae (RO, IIT KGP). © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410109
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  • 3
    Electronic Resource
    Electronic Resource
    Biodegradation of an inhibitory nongrowth substrate (nitroglycerin) in batch reactors (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 79-87 
    Details
    ISSN: 0006-3592
    Keywords: acclimation ; biodegradation ; cometabolism ; ethyl acetate ; explosives ; nitroglycerin ; nongrowth substrate ; primary substrate ; priority pollutants ; sequencing batch reactors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biodegradation of nitroglycerin (NG), an inhibitory, nongrowth substrate present in a multicomponent munition wastewater, was investigated in a pilot-scale batch reactor operated with both aerobic and anoxic cycles. A mixed culture was initially acclimated by gradual introduction of NG into influent and subsequently exposed to actual NG-laden production wastewater. System performance revealed that NG was amenable to aerobic biodegradation without adverse impact on removal efficiencies of other pollutants. Temporal NG concentration profiles indicated that an influent concentration of approximately 200 mg/L of NG was reduced to below detection limits in less than 5 h of aeration with no appreciable (〈4%) biosorption. Failure of NG-acclimated cultures to utilize NG as a sole carbon source in bench-scale reactors suggested that NG behaved as a non-growth substrate and its degradation possibly occurred by cometabolism. Ethyl acetate present in the waste stream was an adequate growth substrate in terms of both biological and physicochemical properties. High concentrations of NO3-N, produced as a result of aerobic degradation of NG and other nitrogenous compounds of the waste, were treated in an anoxic phase. Approximately 95 mg/L of NO3-N was denitrified to below detection limits in 5 h of anoxia without the addition of external carbon sources. Two SRB cycle schemes with different static-fill times exhibited significant differences in treatment efficiencies. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410111
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  • 4
    Electronic Resource
    Electronic Resource
    Yield of poly-D(-)-3-hydroxybutyrate from various carbon sources: A theoretical study (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 165-170 
    Details
    ISSN: 0006-3592
    Keywords: poly-D(-)-3-hydroxybutyrate (PHB) ; theoretical yield ; overall yield ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The theoretical yield of poly-D(-)-3-hydroxybutyrate (PHB) has been estimated from the biochemical pathway leading to PHB when a carbohydrate (glucose), a C1 compound (methanol), a C2 compound (acetic acid), or a C4 compound (butyric acid) is used as a carbon source. In estimating the yield, recycling (or regeneration) of NADP+/ (NADPH + H+) and NAD+ /(NADH + H+) have been taken into account. A special emphasis is made on te regeneration of NADPH, which is the coenzyme of acetoacetyl-CoA reductase, one of three key enzymes involved in the biosynthesis of PHB. As a NADPH-regenerating enzyme, glucose-6-phosphate dehydrogenase or isocitrate dehydrogenase is conceived. An equation which predicts the overall yield of PHB when non-PHB residual biomass is actually formed has been derived as a function of both the theoretical yield and PHB content of the dry cell mass. The ratio of the overall yield to the theoretical yield is roughly proportional to the PHB content. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410122
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  • 5
    Electronic Resource
    Electronic Resource
    Cell-cell adhesion and aggregation: Influence on the growth behavior of CHO cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 188-193 
    Details
    ISSN: 0006-3592
    Keywords: cell-cell adhesion ; CHO cells ; extended growth model ; cluster formation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of cell-cell adhesion on the growth behavior of Chinese hamster ovary (CHO) cells in suspension culture was investigated. CHO cells form aggregates under suboptimal growth conditions. Clusters are formed around decaying and dead cells. The deoxyribonucleic acid (DNA) released from these cells was found to mediate the cells was found to mediate the cell-cell adhesion. Cluster formation dramatically influenced the growth behavior of the cells. First, cells within aggregates showed a strongly reduced specific proliferation rate, and second, shear forces exerted on large aggregates caused a considerable higher specific death rate than those exerted on single cells. These factors led to a reduction of the specific growth rate up to 50%. This decrease could be avoided by addition of DNase 1 to the medium. It is shown that the separate determination of the specific proliferation and death rates is not feasible with state-of-the-art methods. To achieve a more profound and precise description of the growth pattern of animal cells, we propose an extended Monod model and describe the relevant methods. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410204
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  • 6
    Electronic Resource
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    Biofiltration of methanol vapor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 512-524 
    Details
    ISSN: 0006-3592
    Keywords: biofiltration ; biofilter modeling ; methanol ; biodegradation ; VOC emissions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biofiltration of solvent and fuel vapors may offer a costeffective way to comply with increasingly strict air emission standards. An important step in the development of this technology is to derive and validate mathematical models of the biofiltration process for predictive and scaleup calculations. For the study of methanol vapor biofiltration, an 8-membered bacterial consortium was obtained from methanol-exposed soil. The bacteria were immobilized on solid support and packed into a 5-cm-diameter, 60-cm-high column provided with appropriate flowmeters and sampling ports. The solid support was prepared by mixing two volumes of peat with three volumes of perlite particles (i.e., peat-perlite volume ratio 2:3). Two series of experiments were performed. In the first, the inlet methanol concentration was kept constant while the superficial air velocity was varied from run to run. In the second series, the air flow rate (velocity) was kept constant while the inlet methanol concentration was varied. The unit proved effective in removing methanol at rates up to 112.8 g h-1 m-3 packing. A mathematical model has been derived and validated. The model described and predicted experimental results closely. Both experimental data and model predictions suggest that the methanol biofiltration process was limited by oxygen diffusion and methanol degradation kinetics. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410503
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  • 7
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    High cell density cultivation of Pseudomonas oleovorans: Growth and production of poly (3-hydroxyalkanoates) in two-liquid phase batch and fed-batch systems (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 550-556 
    Details
    ISSN: 0006-3592
    Keywords: Pseudomonas oleovorans ; poly(3-hydroxyalkanoate) ; n-octane ; high cell density ; fed-batch culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pseudomonas oleovorans is able to accumulate poly(3-hydroxyalkanoates) (PHAs) under conditions of excess n-alkanes, which serve as sole energy and carbon source, and limitation of an essential nutrient such as ammonium. In this study we aimed at an efficient production of these PHAs by growing P. oleovorans to high cell densities in fed-batch cultures.To examine the efficiency of our reactor system, P. oleovorans was first grown in batch cultures using n-octane as growth substrate and ammonia water for pH regulation to prevent ammonium limiting conditions. When cell growth ceased due to oxygen limiting conditions, a maximum cell density of 27 g ·L-1 dry weight was obtained. When the growth temperature was decreased from the optimal temperature of 30°-18°C, cell growth continued to a final cell density of 35 g · L-1 due to a lower oxygen demand of the cells at this lower incubation temperature.To quantify mass transfer rates in our reactor system, the volumetric oxygen transfer coefficient (kLa) was determined during growth of P. oleovorans on n-octane. Since the stirrer speed and airflow were increased during growth of the organism, the kLa also increased, reaching a constant value of 0.49 s-1 at maximum airflow and stirrer speed of 2 L · min-1 and 2500 rpm, respectively. This kLa value suggests that oxygen transfer is very efficient in our stirred tank reactor.Using these conditions of high oxygen transfer rates, PHA production by P. oleovorans in fed-batch cultures was studied. The cells were first grown batchwise to a density of 6 g · L-1, after which a nutrient feed, consisting of (NH4)2SO4 and MgSO4, was started. The limiting nutrient ammonium was added at a constant rate of 0.23 g NH4+ per hour, and when after 38 h the feed was stopped, a biomass concentration of 37.1 g · L-1 was obtained. The Cellular PHA content was 33% (w/w), which is equal to a final PHA yield of 12.1 g · L-1 and an overall PHA productivity of 0.25 g PHA produced per liter medium per hour. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410507
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  • 8
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    Optimization of fed-batch fermentors by iterative dynamic programming (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 599-602 
    Details
    ISSN: 0006-3592
    Keywords: optimal control ; iterative dynamic programming ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: By using penalty functions to handle state constraints, iterative dynamic programming can be used in a straightforward manner for the optimization of fedbatch fermentors. No computational difficulties were encountered and better results are obtained than previously reported in the literature for a fed-batch fermentor for biosynthesis of penicillin. © 1993 Johy Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410513
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  • 9
    Electronic Resource
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    Factors affecting the performance of crossflow filtration of yeast cell suspension (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 617-624 
    Details
    ISSN: 0006-3592
    Keywords: crossflow filtration ; microfiltration ; baker's yeast ; Saccharomyces cerevisiae ; molasses ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Factors affecting the performance of crossflow filtration were investigated with a thin-channel module and yeast cells. In crossflow filtration of Saccharomyces cerevisiae cells cultivated with YPD medium (Yeast extract, polypeptone, and dextrose) and suspended in saline, a steady state was attained within several minutes when the cell concentration was low and the circulation flow rate was high. The steady-state flux and the change in flux during the initial unsteady state were explained well by conventional filtration theory, with the amount of cake deposited and the mean specific resistance to the cake measured in a dead-end filtration apparatus used in calculation. When the circulation flow rate was lower than a critical value, a part of the channel of the crossflow filtration module was plugged with cell cake, and thus the steady-state flux was low. In crossflow filtration of suspensions of commercially available baker's yeast, the flux gradually decreased, and the flux after 8 h of filtration was lower than the value calculated by filtration theory. Fine particles contaminating the baker's yeast was responsible for the decrease. A similar phenomenon was responsible for the decrease. A similar phenomenon was observed in crossflow filtration of a broth of S. cerevisiae cells cultivated in molasses medium, which also contains such particles, had no effect of the permeation flux during crossflow filtration. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410604
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  • 10
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    Enhancement effect of polyethylene glycol on enzymatic synthesis of cephalexin (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 654-658 
    Details
    ISSN: 0006-3592
    Keywords: polyethylene glycol ; hydrophobicity ; enzymatic synthesis ; cephalexin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In an enzymatic synthesis of cephalexin (CEX) using an acylase from Xanthomonas citri, the effect of polyethylene glycol (PEG) on the synthetic reaction of 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) and D-alpha-phenyl-glycine methyl ester (PGM) to CEX was investigated. The addition of PEG (MW 300-20,000) increased the yield significantly. This yield enhancement effect tended to increase with the increasing molecular weight of PEG. Addition of PEG to the reaction system did not affect both the CEX and PGM hydrolytic reactions. The PEG added to the reaction medium used in these experiments did not depress the water activity significantly, and the product yield improvement could not be explained by the activity alone. The PEG stabilized the enzyme activity to some extent, but this stabilizing effect was only partially attributable to the yield enhancement of CEX. The enhancing effect of PEG on the synthetic yield increased with the increasing PEG molecular weight or the length of the poly(oxy-1,2-ethanediyl) chain, which increases the hydrophobicity of PEG. This finding consequently has led to the conclusion that the PEG structure renders the affinity between enzyme and 7-ADCA, which is a hydrophobic substrate. The microenvironmental hydrophobicity of PEG and its interaction with the hydrophobic substrate was found to be the main reason for the improvement of the CEX yield. In fact, the Michaelis-Menten kinetic constant for 7-ADCA, K7-ADCA in the presence of PEG was smaller than that in the control system (without PEG addition). © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410608
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  • 11
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    A simulation model for the continuous production of acetoin and butanediol using Bacillus subtilis with integrated pervaporation separation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 791-800 
    Details
    ISSN: 0006-3592
    Keywords: acetoin ; butanediol ; Bacillus subtilis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The potential for producing acetoin and butanediol with a Bacillus subtilis strain was investigated with continuous culture using molasses as carbon substrate. The steady-state results were influenced by both oxygen and undetermined limiting compounds. Employing the known metabolic pathways, four overall stoichiometry relations were used with an energetic assumption on the energy requirements for biomass formation to establish a linear relations were used with an energetic assumption on the energy requirements for biomass formation to establish a linear relation between the overall rates, whose parameters were determined by linear regression. This provided a relationship for the product formation rate. The chemostat culture data were described with a growth kinetics model, which included limitation by molasses and oxygen as well as diauxic effects and product inhibition. The biokinetics model was combined with an experimentally verified model for the membrane Pervaporation. From this combined model were determined the influence of the membrane characteristics (enrichment factors and membrane area) and the dilution rate on the performance of the integrated process. Simulations revealed that an increase of the enrichment factor, possible by membrane improvement, would have counteracting influences, owing to decreased product inhibition but with lower biomass concentration. © 1993 Wiley & Sons, Inc.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410805
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  • 12
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    Dramatic enhancement of enzymatic activity in organic solvents by lyoprotectants (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 566-571 
    Details
    ISSN: 0006-3592
    Keywords: enzymes in organic solvents ; lyoprotectants ; imprinting ; lipases ; proteases ; anhydrous media ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When 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.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410509
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  • 13
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    A structured model describing carbon and phosphate limited growth of Catharanthus roseus plant cell suspensions in batch and chemostat culture (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 771-780 
    Details
    ISSN: 0006-3592
    Keywords: Catharanthus roseus ; glucose limitation ; growth kinetics ; phosphate limitation ; plant cell suspension culture ; structured growth model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth of plant cell suspension cultures of Catharanthus roseus in batch fermentors was studied at different initial phosphate levels of the medium. On the basis of the observations and existing knowledge with respect to phosphate metabolism in cultured C. roseus cells, a structured mathematical model was developed for the description of the kinetics of growth and intracellular accumulation of glucose and phosphate, as a function of glucose and phosphate supply. It was shown that the model offers not only good description of the growth of the cells in batch culture at different initial phosphate levels, but also provided a satisfactory description of the growth in glucose limited chemostats. © 1993 Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410803
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  • 14
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    Cadmium biosorption by Saccharomyces cerevisiae (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 826-829 
    Details
    ISSN: 0006-3592
    Keywords: biosorption ; biosorbent ; Saccharomyces cerevisiae ; cadmium biosorption ; metal uptake ; brewer's yeasts ; baker's yeasts ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cadmium uptake by nonliving and resting cells of Saccharomyces cerevisiae obtained from aerobic or anaerobic cultures from pure cadmium-bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal-sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min. © 1993 Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410809
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  • 15
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    The adsorptive immobilization of phospholipids D mediated by calcium ions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 833-836 
    Details
    ISSN: 0006-3592
    Keywords: phospholipase D ; adsorptive immobilization ; calcium ; stabilization ; immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilization of phospholipase D from cabbage was studied with the aim of stabilizing the enzyme for its use in synthesis of phospholipids. It was shown that phospholipase D can be immobilized by adsorption to polymeric carriers containing long chain anchor groups such as octadecyl, octyl, or other alkyl residues. Starting from the crude enzyme, phospholipase D activity is preferentially bound (up to 100%) in competition with contaminating proteins. A prerequisite of high binding rates is the presence of calcium ions, which play a mediating role in the adsorption process. The maximum activity of the carrier-enzyme complexes depends upon the calcium concentration in the immobilization process and the carrier material (≥10mM CaCl2 with octadecyl-Si40, ≥40 mM CaCl2 with octyl-sepharose and butyl-fractogel). Immobilization of phospholipase D to octyl-sepharose was shown to result in a distinctly increased storage stability and an enlarged pH-optimum range for the catalytic activity. Operational stability of different phospholipase D-carrier complexes was compared. © 1993 Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410811
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  • 16
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    Purification and characterization of a highly thermostable glucose isomerase produced by the extremely thermophilic eubacterium, Thermotoga maritima (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 878-886 
    Details
    ISSN: 0006-3592
    Keywords: Thermotoga maritima ; thermophile ; glucose isomerase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermotoga maritima, among the most thermophilic eubacteria currently known, produces glucose isomerase when grow in the presence of xylose. The purified enzyme is a homotetramer with submit molecular Wight of about 45,000. It has a number of features in common with previously described glucose isomerases-pH optimum of 6.5 to 7.5, presence of activesite histidine, requirement for metal cations such as Co2+ and Mg2+, and preference for xylose as substrate. In addition, it has significant sequence/structural homology with other glucose isomerases, as shown by both N-terminal sequencing and immunological crossreactivity. The T. maritima enzyme is distinguished by its extreme thermostability-a temperature optimum of 105 to 110°C, and an estimated half-life of 10 minutes at 120°C, pH 7.0. The high degree of thermostability, coupled with a neutral to slightly acid pH optimum, reveal this enzyme to be a promising candidate for improvement of the industrial glucose isomerization process © 1993 Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410907
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  • 17
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    Masthead (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260411001
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  • 18
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    Continuous, high level production and excretion of a plasmid-encoded protein by Escherichia coli in a two-stage chemostat (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 937-946 
    Details
    ISSN: 0006-3592
    Keywords: protein excretion ; continuous culture ; Escherichia coli ; β-lactamase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The stable continuous overproduction of a plasmidencoded protein, β-lactamase, for at least 50 days by Escherichia coli K-12, RB791(pKN), with release into the culture medium has been demonstrated in two-stage chemostats. The second-stage culture was continuously induced with 0.1 mM IPTG. Continuous expression of β-lactamase could not be sustained with this strain in a single-stage chemostat because of cell death and selection for lac-1 cells. β-Lactamase production in the second stage was sensitive to the second-stage dilution rate and the distribution of the limiting substrate (i.e., glucose) between the first and second stages. The fraction of viable, excreting cells and the average copy number in the induced culture was measurably higher under those conditions of dilution rate and substrate distribution which yielded high β-lactamase levels. The best operating conditions found at 20°C were a first-stage dilution rate of 0.12 h-1, a second-stage dilution rate of 0.03 h-1, and equal glucose feed supplied to each stage. Enzymatically active β-lactamase was produced at a level of 25% of total cellular protein with 90% excretion yielding 300 mg β-lactamase/L that was 50% pure at an OD600 〈 6. © 1993 Wiley & Sons, Inc.
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    Simultaneous enzymatic/electrochemical determination of glucose and L-glutamine in hybridoma media by flow-injection analysis. (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 964-969 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma cultivation media ; glucose ; L-glutamine ; flow-injection analysis ; biosensors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A split-stream flow-injection analysis system is described for simultaneous determination of glucose and L-glutamine in serum-free hybridoma bioprocesses media. Amperometric measurement of glucose is based on anodic oxidation of hydrogen peroxide produced by immobilized glucose oxidase within a triple layer membrane of an integrated flow-through glucose-selective biosensor. Determination of L-glutamine is based on quantitating ammonium ions produced in a flow-through enzymes reactor containing immobilized glutaminase enzyme, and subsequent downstream potentiometric detection of these ions by a nonacting-based ion-selective polymer membrane electrode. Endogenous potassium and ammonium ion interference in the L-glutamine determination are eliminated by using a novel in-line tubular cation-exchange membrane unit to exchange these interferent species for cations undetectable by the membrane electrode. The first generation split-steam flow-injections system can assay 12 samples/h using direct injections of 50 μL of media samples, with linear responses to glucose in the range of 0.03 to 30mM, and log-linear response to L-glutamine from 0.1 to 10 mM. © 1993 Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260411007
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    Masthead (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260411101
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    Kinetic study of the lipase-catalyzed synthesis of triolein (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 1021-1026 
    Details
    ISSN: 0006-3592
    Keywords: Mucor miehei ; Lipozyme ; diolein isomerization ; multiresponse regression ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the synthesis of triolein catalyzed by immobilized Mucor miehei lipase were studied. Equilibrium constants for the synthesis of mono-, di-, and triolein were calculated from the equilibrium compositions for different initial ratios of glycerol and oleic acid by means of multiresponse regression. The 1,3-specific lipase can catalyze the synthesis of triolein because the ester enzymatically formed with the primary alcohol isomerizes, through acyl migration, to an ester on the secondary hydroxyl. The freed primary hydroxyl may then undergo further enzymatic conversion. The rates of isomerization depend on the concentration of oleic acid. © 1993 Wiley & Sons, Inc.
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    Sterilization of various diameter dead-ended tubes (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 125-132 
    Details
    ISSN: 0006-3592
    Keywords: steam-in-place sterilization ; dead-ended tube ; dead-legs ; Bacillus stearothermophilus ; steam sterilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effect of tube diameter on steam-in-place sterilization of dead-ended tubes was studied by examining temperature profiles and rates of kill of Bacillus stearothermophilus spores. Time required for sterilization was determined for 9.4-cm-long tubes with various inside diameters from 0.4 to 1.7 cm. Sterilization time increased with decreasing tube diameter. Experimentally measured kill kinetics in 1.7-cm tubes were in agreement with those predicted if measured temperatures represented saturated steam. A 12-log spore reduction was achieved in 1.7-cm diameter vertical and horizontal tubes in less than 63 minutes. For smaller diameter tubes, entrapped air remained after 2 hours and rates of kill were very dependent on position within the tube, tube diameter, and tube orientation with respect to the gravitational vector. Times to achieve a 1-log drop in spore population in the smaller tubes were as much as 10 times greater than those expected if measured temperatures represented saturated steam. Sterilization was not achieved throughout the 0.4-cm tubes. Recommendations are made for including steam bleeders or using prevaccum cycles for these smaller diameter tubes. © 1993 John Wiley & Sons, Inc.
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    A mathematical model for dynamic simulation of anaerobic digestion of complex substrates: Focusing on ammonia inhibition (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 159-166 
    Details
    ISSN: 0006-3592
    Keywords: anaerobic digestion ; ammonia inhibition ; manure ; mathematical model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model for anaerobic degradation of complex organic material, such as manure, has been developed. The model includes an enzymatic hydrolytic step and four bacterial steps and involves 12 chemical compounds. The model focuses on ammonia inhibition and includes a detailed description of pH and temperature characteristics in order to accurately simulate free ammonia concentration. Free ammonia and acetate constitute the primary modulating factors in the model. The model has been applied for the simulation of digestion of cattle manure in continuously stirred tank reactors (CSTRs), and results compare favorably with experimental data. © 1993 John Wiley & Sons, Inc.
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    Immobilization of β-galactosidase for application in organic chemistry using a chelating peptide (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 178-184 
    Details
    ISSN: 0006-3592
    Keywords: recombinant β-galactosidase fusion protein ; chelating peptide ; immobilized metal affinity chromatography ; immobilized enzyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The strong interaction of hexa-histidine fusion proteins with metal chelate adsorbents was utilized to immobilize β-galactosidase with a hexa-histidine peptide at the N-terminus to the Ni2+-nitrilotriacetic acid adsorbent. The fusion protein was cloned and expressed in Escherichia coli. The purified soluble fusion protein showed the same specific activity as the purified β-galactosidase and retained 64 percent of its β-galactosidase activity when bound to the adsorbent. To demonstrate the potential of the immobilized β-galactosidase in organic chemistry, allyl-β-D-galactosidase was synthesized from lactose and allyl alcohol on a gram scale. The same enzyme preparation was reused in three subsequent batches to prepare the model compound with high yield. © 1993 John Wiley & Sons, Inc.
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    Investigation of subpopulation heterogeneity and plasmid stability in recombinant escherichia coli via a simple segregated model (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 222-234 
    Details
    ISSN: 0006-3592
    Keywords: segregated modeling ; plasmid distribution ; plasmid stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many microbial and cell cultures exhibit phenomena that can best be described using a segregated modeling approach. Heterogeneties are more marked in recombinant cell cultures because subpopulations, which often exhibit different growth and productivity characteristics, are more easily identified by selective markers. A simple segregated mathematical model that simulates the growth of recombinant Escherichia coli cells is developed. Subpopulations of different growth rate, plasmid replication rate, and plasmid segregation probability are explicitly considered. Results indicate that a third mechanism of plasmid instability, referred to here as a “downward selective pressure,” is significant when describing plasmid loss in batch and chemostat cultures. Also, the model agrees well with experimental data from cultures under antibiotic selective pressure. Finally, model simulations of chemostat cultures reveal the importance of initial conditions on culture stability and the possible presence of nonrandom partitioning functions. © 1993 John Wiley & Sons, Inc.
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    Loss of antibody productivity is highly reproducible in multiple hybridoma subclones (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 247-250 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; antibody productivity ; kinetics ; instability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An immunoglobulin G (IgG2b) producing hybridoma cell line (S3H5/γ2bA2) was cloned and subcloned. Twenty subclones were grown in parallel while being adapted in a stepwise fashion to serum-free medium. Following adaptation to serum-free medium, it was found that 16 of the 20 subclones remained at a relatively constant proportion of nonproducing cells. Three of the remaining subclones transiently deviated from this balance but eventually returned toward this population composition. One subclone continued to lose productivity. A population balance was reached at approximately 8% of the population being nonproducers. The loss of antibody productivity was thus highly reproducible. © 1993 John Wiley & Sons, Inc.
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    Masthead (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420301
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    Image analysis to quantify and measure UASB digester granules (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 279-283 
    Details
    ISSN: 0006-3592
    Keywords: image analysis ; UASB digester granules ; sizing ; density ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two-dimensional image analysis was applied to counting, sizing, and density determinations of granules in full-scale and laboratory-scale upflow anaerobic sludge blanket (UASB) digesters. An advantage of this technique for monitoring laboratory-scale digester sludge is the small amount of material required for analysis. Quantification of number of granules using this method correlated well with dry weight determinations (r = 0.989). Distinguished granule size increased with time throughout the digestion process, supported by dry weight determinations which indicated an increase in biomass. The monitoring of granule density may reveal subtleties of the selection pressure placed on granules not noticed previously. © 1993 John Wiley & Sons, Inc.
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    Transport of 1-μm latex particles in pseudomonas aeruginosa biofilms (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 111-117 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; particle ; Pseudomonas aeruginosa ; transport ; roughness ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluorescent latex microbeads added to a Pseudomonas aeruginosa biofilm as tracers of particle movement penetrated the biofilm and remained in it much longer than predicted by a model of advective displacement due to cell growth. Beads with a nominal diameter of 1 μm that were added in the bulk fluid became distributed throughout the biofilm depth. Some microbeads penetrated to the substratum within the 24-h bead addition period. The biofilms had a mean thickness of approximately 34 μm but have been previously shown to be quite rough. Measured rates of bead release from the biofilm corresponded to first order time coefficients of 0.01-0.03 h-1. These bead release rates were approximately an order of magnitude less than the predicted time scale of advective transport, which is just the experimentally measured specific cellular growth rate of 0.15 h-1. Computer simulations of bead transport using the biofilm model BIOSIM were compared with bead release rate data and with bead position distributions within the biofilm as determined by microscopic examination of thin cross sections of embedded biofilm. The model predicted much faster release of beads from the biofilm than actually occurred. It is hypothesized that both the ability of beads to penetrate the biofilm and the unexpectedly low advective displacement velocity of particles in the biofilm were due to the rough nature of the biofilm. © 1993 John Wiley & Sons, Inc.
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    Micelle-supported electroenzymology: Succinate dehydrogenation by escherichia coli fumarate reductase in decylubiquinone and octyl glucoside micelles (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 140-144 
    Details
    ISSN: 0006-3592
    Keywords: fumarate reductase ; succinate dehydrogenation ; micelle-supported electroenzymology ; cyclic voltammetry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The concept of micelle-supported electroenzymology is demonstrated using a system consisting of the membrane enzyme Escherichia coli fumarate reductase (FRD), the amphiphilic coenzyme analogue decylubiquinone (DU), the micelle-forming surfactant n-octyl glucoside (OG), and a gold electrode. The OG micelles provide a hydrophobic, membrane mimetic medium for FRD and DU to exchange electrons while the gold electrode serves to regenerate DU. When succinate is presented to the FRD/DU/OG micelle system, electroenzymatic oxidation of succinate to fumarate occurs as evidenced using cyclic voltammetry. DU is shown to be the only electroactive species in the system; and as increasing amounts of succinate are added, the expected increase in the peak anodic (oxidative) current and decrease in the peak cathodic (reductive) current are observed. The peak anodic current approaches a limiting value with succinate concentration in qualitative agreement with simple Michaelis-Menten enzyme kinetics. When the strong competitive inhibitor oxaloacetate is added, enzymatic oxidation of succinate is inhibited as indicated by no change in the peak anodic and cathodic currents with increasing succinate concentration. © 1993 John Wiley & Sons, Inc.
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    A three-phase pattern in growth, monoclonal antibody production, and metabolite exchange in a hybridoma bioreactor culture (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 133-139 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; kinetics ; curve fitting ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The use of partial cubic spline data interpolation for the calculation of volumetric metabolite exchange rates suggested the existence of three distinct metabolic phases during bioreactor culture of a hybridoma cell line. During phase 1, a rapid amino acid uptake rate and ammonia release rate were observed. The growth rate was low and glutamine synthetase activity fell. In phase 2, maximum growth rate and minimum glutamine assimilation and ammonium production rates were observed. Attempts to corroborate the apparent ammonia assimilation in this phase using 15NH4Cl resulted in low incorporation rates into alanine and glutamine. Maximum glutamine synthetase activity took place during this period. Maximum antibody production rate was observed during phase 3 during which peaks in glutamine assimilation, ammonia release, and glutamine synthetase activity were observed. The apparent existence of the three phases prompted us to carry out Northern blot analysis of glutamine synthetase RNA at appropriate times during the process. This revealed a pattern of appearance and dis-appearance of mRNA consistent with the three phases indicated by the fermentation parameters. © 1993 John Wiley & Sons, Inc.
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    Observations of aerobic, growing escherichia coli metabolism using an on-line nuclear magnetic resonance spectroscopy system (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 215-221 
    Details
    ISSN: 0006-3592
    Keywords: on-line NMR ; phosphorus-31 NMR ; Escherichia coli ; aerobic and anaerobic metabolism ; intracellular pH ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental system has been constructed which enables on-line measurements of phosphorus-31 (31P) nuclear magnetic resonance (NMR) spectra for growing bacterial suspensions under anaerobic or aerobic conditions. A sample stream from a laboratory bioreactor is circulated to the NMR sample chamber in a gas exchange system which permits maintenance of aerobic conditions for high-cell-density cultures. 31P NMR spectra with resolution comparable with those obtained traditionally using dense, concentrated, nongrowing cell suspensions can be obtained at cell densities above 25 g/L with acquisition times ranging from 14 to 3 minutes which decline as cell density increases. This system has been employed to characterize the changes in intracellular state of a stationary phase culture which is subjected to a transition from aerobic to anaerobic conditions. Both intracellular NTP level and cytoplasmic pH are substantially lower under anaerobic conditions. Also, the system has been employed to observe the response of a growing culture to external addition of acetate. Cells are able to maintain pH difference across the cytoplasmic membrane at extracellular acetate concentrations of 5 and 10 g/L. However, acetate concentrations of 20 g/L cause collapse of the transmembrane ΔpH and sharp reduction of the growth rate of the culture. The experimental configuration described should also permit NMR observations of many other types of microbial cultures and of other nuclei. © 1993 John Wiley & Sons, Inc.
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    Expression of epoxide hydrolase in insect cells: A focus on the infected cell (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 240-246 
    Details
    ISSN: 0006-3592
    Keywords: insect cell culture ; baculovirus expression ; serum-free media ; insect cell metabolism ; cell phase ; high cell density expression ; epoxide hydrolase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Insect cell culture and the baculovirus vector expression system have emerged to be a promising production technique for heterologous proteins. In this article, expression characteristics for membrane-bound epoxide hydrolase are examined. A generic process is presented whereby cells are grown in serum-free media supplemented with serum and then resuspended in serum-free media to simplify purification after infection. The infected cells retain significant metabolic activity during the postinfection stage. Thus, maintaining nutrient supply during the postinfection period is critical, and a low stirring rate will result in oxygen depletion and shift the metabolism of the infected cells toward lactate production which then lowers product yield. This is the first report indicating that glucose is supplied from sucrose decomposition and then metabolized for viral DNA and recombinant protein production in recombinant baculovirus insect expression system. © 1993 John Wiley & Sons, Inc.
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    A bioassay of thyrotrophin by photografted mammalian cells onto polymeric supportsPart 28 of the series “Photosynthetic Membranes.” (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 255-259 
    Details
    ISSN: 0006-3592
    Keywords: thyroid cells ; immobilization ; photografting ; photocatalyst ; thryrotrophin bioassay ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Viable and functionally responsive human thyroid follicular cells, suspended in a commercial polyester acrylate diluted with tripropyleneglycol diacrylate, photoinitiated, and photocatalyzed with a proprietary photocatalytic system based on a synergic mixture of vanadium (V) t-butoxide and i-propoxide, have been immobilized as monolayers onto polystyrene plates. Bioassay of thyrotrophin in immobilized cell cultures yielded, by log-log plot of the dose-response curve, a slope (0.92 ± 0.02) in close agreement with that (0.91) reported for cells immobilized by physical adsorption. The decisive role of photocatalyst in the photografting procedure has also been shown experimentally. A mechanism is suggested by which cells are anchored, rapidly and with stable chemical bonds, onto one of the two acrylate functions of the monomer-prepolymer mixture, the other one being simultaneously responsible for photochemical grafting onto the support. © 1993 John Wiley & Sons, Inc.
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    Analytical effectiveness calculations concerning the degradation of an inhibitive substrate by a steady-state biofilm (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 267-278 
    Details
    ISSN: 0006-3592
    Keywords: biocatalyst ; immobilization ; analytical effectiveness factor ; substrate inhibition ; phenol degradation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A reaction engineering model for the degradation of an inhibitory substrate by a steady-state biofilm is presented. The model describes both the metabolic rate controlling behavior of this substrate in the biofilm and the effect of diffusion limitation caused by an arbitrary substrate on the active biofilm thickness. An analytical expression for the biocatalyst effectiveness factor is presented on the basis of Pirt kinetics for cell maintenance, first order substrate inhibition kinetics, and zero order substrate consumption kinetics. The proposed expression for the biocatalyst effectiveness factor is much more convenient to incorporate into a macroreactor model than the numerical alternatives. Simple criteria are presented to check the applicability of the model in case of true Monod kinetics. The analytical solution is expected to be particularly applicable to processes where a low soluble organic substrate controls the biomass growth, a situation which is often met in wastewater purification processes of industrial importance. The degradation of phenol by Pseudomonas sp. is treated as an example. © 1993 John Wiley & Sons, Inc.
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    Determination of cellular rate distributions in microbial cell populations: Feeding rates of ciliated protozoa (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 284-294 
    Details
    ISSN: 0006-3592
    Keywords: ingestion rate distribution ; population balance ; state properties ; rate properties ; flow cytometry ; particle uptake model ; Poisson process model ; Tetrahymena pyriformis ; suspension feeding ; filter feeding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel procedure is proposed for determining distributions of rate properties and correlations of rate with state properties of microbial cell populations. The procedure is novel in that it uses transient data, and thus, it does not require that the population be in balanced growth, although it requires that the population structure does not change during the short transient experiment. The procedure is applied to populations of the ciliated protozoan Tetrahymena to determine ingestion rate variability. The number of ingested microspheres per cell and the single-cell protein content - an indicator of cell size - were directly determined with dual-color flow cytometry. The proposed technique revealed the correlation pattern of the particle ingestion rate with cell size. In particular, ingestion rate was found to be positively correlated with cell size for the smaller feeding cells and to be uncorrelated with size for the larger cells. Using the fact that particle uptake from dilute particle suspensions is a Poisson random process, we determined that the coefficient of variation of the distribution of ingestion rates within the feeding population is about 50%. It was concluded that the dynamics of particle ingestion can be accurately described only if it is realized that particle ingestion rates are distributed. © 1993 John Wiley & Sons, Inc.
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    Activated sludge process performance using a multistage tower aeration tank (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 315-325 
    Details
    ISSN: 0006-3592
    Keywords: multistage tower aeration tank ; activated sludge process ; kinetics ; Peclet number ; dispersion model ; simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study's objective was to clarify both experimentally and theoretically whether a vertical multistage tower aeration tank system is advantageous as compared with a completely mixed system, particularly with respect to purification efficiency, sludge settleability, and excess sludge production. In comparing the two systems: (1) purification efficiency in the multistage tower aeration system with partial fluid mixing with a large Peclet number was higher than in a corresponding completely mixed system for all applied organic loadings; (2) the multistage tower aeration system had some definite advantages with respect to sludge settleability and excess sludge production; (3) the activated sludge system's higher performance with partial fluid mixing was shown quantitatively with the axial dispersion model in conjunction with growth kinetics which involved rapid uptake such as biosorption and subsequent oxidative biodegradation processes of organic substances. © 1993 John Wiley & Sons, Inc.
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    Microencapsulation selection for isolation of yeast mutants with increased secretion of Aspergillus awamori glucoamylase (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 351-356 
    Details
    ISSN: 0006-3592
    Keywords: microencapsulation ; selection ; secretion ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have developed a microencapsulation selection method which allows the rapid and quantitative screening of 〉106 yeast cells for enhanced secretion of Aspergillus awamori glucoamylase. The method provides a 400-fold single-pass enrichment for high-secreting mutants, and can be straightforwardly adapted for application to growth-based selection schemes with other microorganisms and enzymes. © 1993 John Wiley & Sons, Inc.
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    A two-stage bioreactor system for the production of recombinant proteins using a genetically engineered baculovirus/insect cell system (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 357-366 
    Details
    ISSN: 0006-3592
    Keywords: bioreactor ; insect cell culture ; high-density cell culture ; recombinant baculovirus ; chloramphenicol acetyltransferase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A two-stage bioreactor scheme was developed for the large-scale production of recombinant proteins using a genetically engineered baculovirus/insect cell system. The first bioreactor was employed for cell growth and the second for cell infection. Silkworm Bm5 cells were infected with a recombinant baculovirus, BmNPV/P5.cat, containing a bacterial chloramphenicol acetyltransferase (CAT) gene under the control of the polyhedrin gene promoter of Bombyx mori nuclear polyhedrosis virus (BmNPV). This recombinant baculovirus has been used as an expression vector for the production of recombinant CAT enzyme. A specific productivity of 82 to 90 μg CAT/(106 cells) was obtained using the BmNPV/Bm5 expression system, a yield similar to that achieved using the AcNPV/Sf expression system. Repeated infection of high-density cell cultures did not reduce the specific productivity of the CAT enzyme. Most importantly, the problems associated with the infection of high-density cell cultures were resolved by means of controlled infection conditions and appropriate replenishment of spent culture medium following infection. The glucose uptake rate by the cells following infection was 50% higher than that by the cells before infection. Not only did the infection of high-density cell cultures result in consistent yields of 250 mg/L of CAT enzyme, but also the two-stage bioreactor system was proven to be reliable for a long-term operation beyond 600 h. © 1993 John Wiley & Sons, Inc.
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    Immobilization of enzyme onto cellulose-titanium oxide composite fiber (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 394-397 
    Details
    ISSN: 0006-3592
    Keywords: cellulose ; immobilization ; fiber ; titanium oxide ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fibers of a cellulose-TiO2 composite were prepared by the reaction of cellulose with titanium iso-propoxide. Enzymes were immobilized on the fibers easily and simply under mild conditions. The fibers were stable in common solvents, high ionic solutions, and over a wide range of pH values 3-10. © 1993 John Wiley & Sons, Inc.
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    A new approach for modeling cellulase-cellulose adsorption and the kinetics of the enzymatic hydrolysis of microcrystalline cellulose (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 469-479 
    Details
    ISSN: 0006-3592
    Keywords: cellulase ; cellulose ; adsorption ; kinetics ; mathematical model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two fractions of substrate in microcrystalline cellulose which differ in their adsorption capacities for the cellulases and their susceptibility to enzymatic attack have been identified. On the basis of a two-substrate hypothesis, mathematical models to describe enzyme adsorption and the kinetics of hydrolysis have been derived. A new nonequilibrium approach was chosen to predict cellulase-cellulose adsorption. A maximum binding capacity of 76 mg protein per gram substrate and a half-maximum saturation constant of 26 filter paper units (FPU) per gram substrate have been calculated, and a linear relationship of hydrolysis rate vs. adsorbed protein has been found. The fraction of substrate more easily hydrolyzed, as calculated from hydrolysis data, represents 19% of the total effective substrate concentration. This fraction is only slightly different from that of other celluloses and has been estimated to be 27% and 30% for NaOH- and H3PO4-swollen cellulose, respectively. The effective substrate concentration is equal to the maximum amount of the substrate which can be converted during exhaustive hydrolysis. This in turn is determined by the overall degradability of the substrate by the cellulases (85-90% for microcrystalline cellulose) and by the cellobiose concentration during hydrolysis. The kinetic model is based on a summation of two integrated first-order reactions with respect to the effective substrate concentration. Furthermore, it includes the principal factors influencing the reaction rates: the ratio of filter paper and β-glucosidase units per gram substrate and the initial substrate concentration. © 1993 John Wiley & Sons, Inc.
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    Detection of bacterial contamination in cultures of eucaryotic cells by gas chromatography-mass spectrometry (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 421-429 
    Details
    ISSN: 0006-3592
    Keywords: bacterial contamination ; eucaryotic cultures ; detection ; chromatography ; mass spectrometry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The use of gas chromatography-mass spectrometry for early detection of bacterial contaminations in cultures of baker's yeast, Penicillium chrysogenum, and an animal cell line was evaluated; muramic acid and characteristic cellular fatty acids were used as analytes. By analyzing branched-chain and cyclopropane-substituted fatty acids as methyl esters, Staphylococcus epidermidis, Bacillus subtilis, Lactobacillus reuteri, Enterobacter cloacae, and Pseudomonas fluorescens were detected in a 500-fold excess (w/w) of baker's yeast; the amounts injected corresponded to 300 ng (dry mass) of the bacteria. Contamination with Bacillus was detected in cultures of Penicillium chrysogenum and animal cells by analyzing muramic acid, both as its alditol acetate derivative, using electron impact ionization, and its trifluoroacetyl methyl glycoside derivative, using negative ion-chemical ionization. The trifluoroacetylated derivative was detected in injected amounts corresponding to 1 × 103 bacterial cells in the contaminated animal cell line, whereas amounts corresponding to 1 × 105 bacteria were required for detection of the alditol acetate derivative; the amounts in the original samples were 5 × 105 and 5 × 106, respectively. However, the alditol acetate method exhibited lower chemical interferences than the trifluoroacetyl methyl glycoside procedure. The results show the potential of using gas chromatographic-mass spectrometric analysis of cellular constituents for the detection of bacterial contaminations in eucaryotic cultures as an alternative to conventional microbiological methods. © 1993 John Wiley & Sons, Inc.
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    Stabilization of heterodimeric enzyme by multipoint covalent immobilization: Penicillin G acylase from Kluyvera citrophila (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 455-464 
    Details
    ISSN: 0006-3592
    Keywords: penicillin G acylase ; Kluyvera citrophila ; immobilization-stabilization of penicillin G acylase ; stabilization of multimeric enzymes ; reactivation of enzyme derivatives ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We have developed a strategy for immobilization-stabilization of penicillin G acylase (PGA) from Kluyvera citrophila by controlled multipoint covalent attachment to agarose-aldehyde gels. This enzyme is composed by two dissimilar subunits noncovalently bound. Thus, in this article we establish clear correlations between enzyme stabilization and the multipoint immobilization and/or between enzyme stabilization and the involvement of the two subunits in the attachment of them to the support. We have demonstrated that important thermal stabilizations of derivatives were only obtained through a very intense enzyme-support multipoint attachment involving the whole enzyme molecule. In this way, we have prepared derivatives preserving more than 90% of catalytic activity and being more than 1000-fold more stable than soluble and one-point attached enzyme. In addition, the involvement of the two subunits in the covalent attachment to the support has proved to be essential to develop interesting strategies for reactivation of inactivated enzyme molecules [e.g., by refolding of immobilized PGA after previous unfolding with urea and sodium dodecyl sulfate (SDS)]. © 1993 John Wiley & Sons, Inc.
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    Controlled release process to recover heterologous glycosylphosphatidylinositol membrane anchored proteins from CHO cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 480-486 
    Details
    ISSN: 0006-3592
    Keywords: CHO ; PI-PLC ; heterologous glipiated proteins ; controlled release ; GPI anchor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A semicontinuous process has been developed to recover heterologous proteins at increased concentrations and purities. Proteins attached to mammalian cell membranes by glycosylphosphatidylinositol (GPI) anchors can be selectively released into the supernatant by the enzyme phosphatidylinositol-phospholipase C (PI-PLC). Chinese hamster ovary (CHO) cells, genetically engineered to express the GPI anchored, human melanoma antigen (p97), were used as a model system. These cells were grown in protein containing growth medium. During a brief harvesting phase the medium was replaced by phosphate buffered saline (PBS) containing 10 mU/mL of PI-PLC and the GPI anchored protein was cleaved from the cell surface and recovered in soluble form at up to 30% purity. After harvesting, the cells were returned to growth medium where the protein was re-expressed within 40 h. The growth rate, viability, and protein production of cells, repeatedly harvested over a 44-day period, were not adversely affected. This continuous cyclic harvesting process allowed recovery of a heterologous protein at high purity and concentrations and could be applied to the recovery of other GPI anchored proteins and genetically engineered GPI anchored fusion proteins. © 1993 John Wiley & Sons, Inc.
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    Enhanced recovery of solavetivone from Agrobacterium transformed root cultures of Hyoscyamus muticus using integrated product extraction (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 503-508 
    Details
    ISSN: 0006-3592
    Keywords: root culture ; fungal elicitation ; feedback inhibition ; in situ extraction ; adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The integrated recovery of solavetivone from fungus elicited “hairy root” cultures of Hyoscyamus muticus is examined using volatile organic solvents and solid-phase adsorbents in an external loop extraction configuration. Hexane and pentane are shown to be toxic when added directly to the culture; however, growth of roots is not inhibited when cultures are exposed to media saturated with these hydrocarbons. Solid-phase neutral adsorbents, XAD-7 and XAD-16, display higher capacity and better solavetivone partitioning capability than the hydrocarbons; however, their selectivity for the sesquiterpene solavetivone is poor in comparison with hexane. In both cases, the integration of product recovery through extraction resulted in a doubling of product formation by alleviating feedback repression. Implications of these results to the recovery of secondary metabolites from plant root cultures are discussed. © 1993 John Wiley & Sons, Inc.
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    A thermodynamically based correlation for maintenance gibbs energy requirements in aerobic and anaerobic chemotrophic growth (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 509-519 
    Details
    ISSN: 0006-3592
    Keywords: Gibbs energy requirements ; chemotrophic growth ; maintenance ; anaerobic and aerobic ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A thermodynamic framework has been provided for the description of maintenance requirements of microorganisms. The central parameter is the biomass specific Gibbs energy consumption for maintenance, mE (kJ/C-mol biomass · h). A large set of data has been used including (i) a large range of different organisms (bacteria, yeasts, plant cells), (ii) mixed cultures, (iii) heterotrophic and autotrophic growth, (iv) growth under aerobic and anaerobic conditions, and (v) a large temperature range (5-75°C). It appears that only the temperature has a major influence, with an energy of activation of 69 kJ/mol. Different electron donors or electron acceptors only show a very minor influence on mE. On the basis of the data set, temperature correlations of mE have been derived for aerobic and anaerobic growth. The generalized concept for maintenance Gibbs energy is used to establish a correlation which allows the estimation of the biomass yield on electron donor as a function of C-source, electron donor, electron acceptor, N source, growth rate, and temperature. The advantage of using the mE parameter over other maintenance-related parameters (like μe, mO2, mD, γDmD) is discussed. © 1993 John Wiley & Sons, Inc.
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    Cultivation of virus antigen in fibroblast cells using a glass fiber bed reactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 635-642 
    Details
    ISSN: 0006-3592
    Keywords: MRC-5 ; anchorage-dependent ; fibers ; cell culture ; hepatitis A ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The anchorage-dependent cell line, MRC-5, was cultivated successfully on glass fibers with diameters ranging from 24 to 120 μm, despite vast differences in substrate curvature. Multilayer cell growth was observed, particularly for fiber diameters 30 μm and below, which differed from the typical monolayer growth observed in T-flask cultivations. Cells were maintainable at a reduced incubation temperature and were demonstrated to support virus replication for the 21-day antigen production period. Direct microscopic observation, along with indirect calculations, indicated that only a small fraction (about 10%) of the total available fiber surface area was occupied by cells. Thus, productivity per unit surface area was replaced by productivity per unit medium volume when evaluating fiber bed performance. Antigen and protein yields, as well as nutrient uptakes, were 1.5- to 2.5-fold greater than parallel T-flask cultures when compared on this basis. Corresponding available surface area-based values were 10- to 15-fold lower for the fiber bed reactor. The multilayer cell morphology obtained in the fiber bed was attractive for antigen production when immobilized in a column reactor system. © 1993 John Wiley & Sons, Inc.
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    Gas phase acetaldehyde production in a continuous bioreactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 667-673 
    Details
    ISSN: 0006-3592
    Keywords: alcohol oxidase ; acetaldehyde ; ethanol ; continuous bioreactor ; gas phase reaction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The gas phase continuous production of acetaldehyde was studied with particular emphasis on the development of biocatalyst (alcohol oxidase on solid phase support materials) for a fixed bed reactor. Based on the experimental results in a batch bioreactor, the biocatalysts were prepared by immobilization of alcohol oxidase on Amberlite IRA-400, packed into a column, and the continuous acetaldehyde production in the gas phase by alcohol oxidase was performed. The effects of the reaction temperature, flow rates of gaseous stream, and ethanol vapor concentration on the performance of the continuous bioreactor were investigated. © 1993 John Wiley & Sons, Inc.
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    Response dynamics of 26-, 34-, 39-, 54-, and 80-kDa proteases in induced cultures of recombinant Escherichia coli (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 675-685 
    Details
    ISSN: 0006-3592
    Keywords: stringent response ; E. coli protease ; recombinant E. coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several researchers have demonstrated that the presence of a heterologous protein in recombinant Escherichia coli elicits a response similar to the heat-shock response, which includes enhanced protease expression. The present work detects, quantifies, and characterizes intracellular protease activity in E. coli that are “shocked” by the induction of a recombinant protein, CAT, which is an endogenous protein in some E. coli strains. A novel, sodium dodecyl sulfate gelatin poly-acrylamide gel electrophoresis (SDS-GPAGE) method is used to detect, quantify, and characterize the presence of these proteases. A hypothesis is proposed which links the amplified protease activity to a temporary depletion of specific amino acid pools, and a stringent-like stress response. © 1993 John Wiley & Sons, Inc.
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    A single-cell assay of β-galactosidase in recombinant Escherichia coli using flow cytometry (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 708-715 
    Details
    ISSN: 0006-3592
    Keywords: flow cytometry ; recombinant E. coli ; β-galactosidase assay ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A flow cytometric method was developed for the assay of β-galactosidase in single Escherichia coli cells. A new fluorogenic substrate for β-galactosidase, C12FDG, contains a lipophilic group that allows the substrate to penetrate through cell membranes under normal conditions. When the substrate is hydrolyzed by intracellular β-galactosidase, a green fluorescent product is formed and retained inside the cell. Consequently, the stained β-galactosidase-positive cells exhibit fluorescence, which is detected by flow cytometry. This new assay was used to analyze the segregational instability caused by a reduction in specific growth rate of the plasmid-bearing cells in the T7 expression system. Induction results in a substantial accumulation of intracellular β-galactosidase along with a rapid increase in the fraction of plasmid-free cells. Once the cells lose the plasmid, they no longer produce β-galactosidase, which is reduced by at least half every generation; thus, after staining, the fluorescent, plasmid-bearing cells can be distinguished from the nonfluorescent, plasmid-free cells using flow cytometry. This article describes the feasibility of the flow cytometric assay for single E. coli cells and reports the optimal assay conditions. A direct relationship between β-galactosidase activity and green fluorescence intensity was found, and the fractions of recombinant cells in batch cultures were analyzed after various levels of induction. © 1993 John Wiley & Sons, Inc.
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    Optimal operating policy of the ultrafiltration membrane bioreactor for enzymatic hydrolysis of cellulose (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 737-746 
    Details
    ISSN: 0006-3592
    Keywords: Optimal dilution rate ; cellulose hydrolysis ; membrane bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dilution rate of an ultrafiltration membrane bioreactor in the enzymatic hydrolysis of cellulose was optimized using the kinetic model developed by Fan and Lee.4 The sequence of optimal dilution rates was found to generally consist of an initial period of a minimal value (batch period), a subsequent period of maximum dilution rate, a period of a second batch, and a final period of a singular dilution rate. The effects of operating conditions, such as β-glucosidase activity, operating time, maximum dilution rate, substrate feeding rate, and enzyme-to-substrate ratio on both the conversion yield and the sequence of optimal dilution rates were investigated. To evaluate the validity of kinetic model employed in this work, enzymatic hydrolysis was carried out using α-cellulose as a substrate in the ultrafiltration membrane bioreactor. The experimental data were well consistent with the simulation results. © 1993 John Wiley & Sons, Inc.
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    Modeling lipolysis in a reversed micellar system: Part II - membrane reactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 765-771 
    Details
    ISSN: 0006-3592
    Keywords: lipolysis ; lipases ; reversed micelles ; modeling ; second-order model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Olive oil hydrolysis using Chromobacterium viscosum lipase B in a reversed micellar media was investigated in a membrane reactor. The dynamic evolution of the product concentration both in the concentrate and permeate stream was analyzed using a mechanistic model previously developed by us and further modified in this work. A kinetic law with a second-order dependence in the substrate concentration and nonlinear product inhibition was found to be the most adequate for the description of the hydrolysis data over an extensive range of time and substrate concentration. These findings are discussed in terms of the specific interactions occurring in the membrane reactor. © 1993 John Wiley & Sons, Inc.
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    Morphological measurements on Penicillium chrysogenum broths by rheology and filtration methods (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 777-784 
    Details
    ISSN: 0006-3592
    Keywords: rheology ; filtration ; mycelial ; morphology ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The morphology parameters of mycelial culture (Penicillium chrysogenum) were measured and quantified by rheology and filtration methods. Two of the morphology parameters obtained from rheology measurements, δ defined by the Casson equation and δ* defined by intrinsic viscosity, were found to vary systematically with broth age and with the observed morphology by microscopy. Three of the filtration parameters, hyphal density, Kozeny constant, and index of compressibility, are demonstrated as sensitive indicators of the broth age and mycelial morphology. Two of the morphology parameters, δ and δ*, were used to cross-correlate with hyphal density. Because various mycelial fermentations require different growth morphologies (pellet and filament) for optimum product yield and the morphology of mycelial broths varies with broth age, it is suggested that these morphology parameters could be used to represent the morphology of mycelial broths quantitatively. © 1993 John Wiley & Sons, Inc.
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    Masthead (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1002/bit.260420701
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    Improvement of shikonin productivity in Lithospermum erythrorhizon cell culture by alternating carbon and nitrogen feeding strategy (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 793-799 
    Details
    ISSN: 0006-3592
    Keywords: L. erythrorhizon ; shikonin ; carbon and nitrogen feeding ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stationary phase cell suspension cultures of Agrobacterium tumefaciens transformed Lithospermum erythrorhizon respond to additions of sucrose-rich (C-rich) medium with a 2-3-fold increase in the accumulation of shikonin derivatives and a 3-3.5-fold increase in the accumulation of soluble phenolics while showing a modest (10-30%) increase in cell concentration. Conversely, the addition of nitrate-rich (N-rich) medium resulted in 25-35% increase in biomass concentration but only 2-9% increase in shikonin production and ∼ 3% increase in the yield of soluble phenolics. Repeated additions of C-rich medium resulted in only a modest (less than 10%) improvement in shikonin production over the levels obtained after the first application. No obvious correlation could be discerned between intracellular ATP levels or protein synthesis patterns and the pattern of shikonin accumulation following the addition of C-rich medium, suggesting that the precursor diversion mechanism is not generally applicable in our cell line. It was found that alternating feeding of N-rich and C-rich media could be used as an effective strategy for enhancing the productivity of plant secondary metabolite. © 1993 John Wiley & Sons, Inc.
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    Application of computer to monitoring and control of fermentation process: Microbial conversion of ML-236B Na to pravastatin (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 815-820 
    Details
    ISSN: 0006-3592
    Keywords: pravastatin ; ML236B sodium salt ; computer coupled control system ; HPLC ; on-line monitoring ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An automatic feeding process for microbial hydroxylation of ML236B sodium salt (ML-236B Na; compactin) by Streptomyces carbophilus SANK 62585 was developed. The hydroxylated product, pravastatin sodium salt (pravastatin; trade name Mevalotin), is an inhibitor of 3-hydroxy-3-methyglutaryl-coenzyme A reductase (HMG-CoA reductase) used as cholesterol-lowering drug. The hydroxylation activity of S. carbophilus was induced by the addition of ML236B Na to culture broth but inhibited by high concentration of ML236B Na. In order to obtain high conversion yield, it was necessary to maintain optimum ML236B Na concentration throughout the fermentation by continuous feeding. For this purpose, we developed an on-line monitoring method, which mainly consisted of a cross-flow filtration module, high-performance liquid chromatography (HPLC) analyzer, feed pump, and microcomputer for regulation of ML236B Na concentration. An algorithm for control of ML236B Na feed rate based on feedback and feed-forward control where conversion rate after Δt was estimated by using regression analysis of the five latest values of conversion rate. In a fed-batch culture employing this system, the concentration of ML236B Na was maintained at optimum level during the fermentation and the productivity of pravastatin was increased threefold over that obtained in manual control culture. © 1993 John Wiley & Sons, Inc.
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    Stimulation of acid phosphatase induction in Saccharomyces cerevisiae by electrochemical modulation of effector concentration (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 836-842 
    Details
    ISSN: 0006-3592
    Keywords: acid phosphatase ; yeast ; enzyme induction ; electrochemical modulation ; PHO gene ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel modulating method of the expression of Saccharomyces PHO 5 gene, responsible for acid phosphatase (APase), is proposed. The method is based on electrochemical modulation of an effector (inorganic phosphate) concentration, as the gene expression is initiated below a threshold concentration of phosphate and is terminated above the threshold value. By positioning the yeast in the close neighborhood of a conducting polymer, the authors show the effectiveness of the electrochemical approach toward PHO 5 induction. Based on the approach, phosphate concentration is easily modulated at the boundary concentration by taking advantage of anion doping-undoping at a conducting polymer and the resulting anion localization-delocalization in the polymer, as the local enrichment of phosphate in the polymer results in the lowering of phosphate in the vicinity of polypyrrole. External phosphate concentration is thus electrochemically modulated when the conducting polymer is positioned in the close neighborhood of the yeast cells; thereby the PHO gene is induced. Here an electrochemical approach for the APase expression as a strategy of selective induction of specific genetic information is described. © 1993 John Wiley & Sons, Inc.
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    Perfusion strategy for rosmarinic acid production by Anchusa officinalis (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 884-890 
    Details
    ISSN: 0006-3592
    Keywords: perfusion culture ; Anchusa officinalis ; rosmarinic acid ; medium exchange ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The production of an intracellular secondary metabolite rosmarinic acid (RA) by plant cell suspensions of Anchusa officinalis cultivated with intermittent medium exchange is investigated. Initially, a two-stage perfusion culture method was employed. After being cultured in the batch mode for ca. 6 days in B5 medium plus 3% sucrose, 1 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D), and 0.1 mg/L kinetin (2,4-D B5 medium), Anchusa culture was cultivated to high cell density by perfusion during the growth stage using a hormone-free Gamborg B5 medium supplemented with 6% sucrose. This was followed by a production stage, in which a complete medium exchange into B5 medium plus 3% sucrose and 0.25 mg/L naphthleneacetic acid (NAA) was conducted. The two-stage perfusion culture had a higher maximum culture RA concentration but a lower RA content per cell than the batch stock culture maintained in the 2,4-D B5 medium. Higher culture RA concentration was due primarily to high cell density. The high packed cell volume, however, seemed to reduce the synergistic effect of NAA on RA synthesis. Subsequently, a single-stage perfusion culture method was investigated. The best result was obtained by growing the culture in the batch mode for ca. 10 days using B5 medium supplemented with 3% sucrose and 0.25 mg/L NAA, followed by perfusing the culture with B5 medium plus 6% sucrose and 0.25 mg/L NAA at a constant perfusion rate of 0.1/day. A maximum cell dry weight of 35 g/L and a RA concentration of almost 4 g/L were achieved. This is the highest RA concentration ever reported in the Anchusa culture. © 1993 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260420713
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    A two-plane tubular photobioreactor for outdoor culture of Spirulina (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 891-898 
    Details
    ISSN: 0006-3592
    Keywords: photobioreactor ; biomass productivity ; Spirulina viscosity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A photobioreactor in the form of a 245-m-long loop made of plexiglass tubes having an inner diameter of 2.6 cm was designed and constructed for outdoor culture of Spirulina. The loop was arranged in two planes, with 15 8-m-long tubes in each plane. In the upper plane, the tubes were placed in the vacant space between the ones of the lower plane. The culture recycle was performed either with two airlifts, one per plane, or with two peristaltic pumps. The power required for water recycle in the tubular photobioreactor, with a Reynolds number of 4000, was 3.93 × 10-2 W m-2. The photobioreactor contained 145 L of culture and covered an overall area of 7.8 m2. The photobioreactor operation was computer controlled. Viscosity measurements performed on Spirulina cultures having different biomass concentrations showed non-Newtonian behavior displaying decreasing viscosity with an increasing shear rate. The performance of the two-plane photobioreactor was tested under the climatic conditions of central Italy (latitude 43.8° N, longitude 11.3° E). A biomass concentration of 3.5 g L-1 was found to be adequate for outdoor culture of Spirulina. With a biomass concentration of 6.3 g L-1, the biomass output rate significantly decreased. The net biomass output rate reached a mean value of 27.8 g m-2 d-1 in July; this corresponded to a net photosynthetic efficiency of 6.6% (based on visible irradiance). © 1993 John Wiley & Sons, Inc.
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    Foreign gene expression (β-galactosidase) during the cell cycle phases in recombinant CHO cells (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1113-1123 
    Details
    ISSN: 0006-3592
    Keywords: cell cycle analysis ; β-galactosidase ; gene expression, foreign ; dihydrofolate reductase ; recombinant CHO cells ; cytomegalovirus promoter ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant mammalian cultures for heterologous gene expression typically involve cells traversing the cell cycle. Studies were conducted to characterize rates of accumulation of intracellular foreign protein in single cells during the cell cycle of Chinese hamster ovary (CHO) cells transfected with an expression vector containing the gene for dihydrofolate reductase (dhfr) and the lacZ gene for bacterial β-galactosidase (a nonsecreated protein). The lacZ gene was under the control of the constitutive cytomegalovirus promoter. These normally attachment-grown cells were adapted to suspension culture in 10-7 M methotrexate, and a dual-laser flow cytometer was used to simultaneously determine the DNA and foreign protein (β-galactosidase) content of single living cells. Expression of β-galactosidase as a function of cell cycle phase was evaluated for cells in the exponential growth phase, early plateau phase, and inhibited traverse of the cell cycle during exponential growth. The results showed that the β-galactosidase production rate is higher in the S phase than that in the G1 or G2/M phases. Also, when cell cycle progression was stopped at the S phase by addition of aphidicolin, β-galactosidase content in single cells was higher than that in exponential phase or plateau phase cells and increased with increasing culture time. Although the cells did not continue to divide after aphidicolin addition, the production of β-galactosidase per unit volume of culture was very similar to that in normal exponential growth. © 1993 John Wiley & Sons, Inc.
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    Enhanced production of α-amylase in fed-batch cultures of Bacillus subtilis TN106[pAT5] (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1142-1150 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus subtilis ; recombinant species ; recombinant protein ; fed-batch culture ; arginine limitation ; α-amylase ; hydrolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Growth of Bacillus subtilis TN106[pAT5] and synthesis of plasmid-encoded protein (α-amylase) are investigated in batch, continuous, and fed-batch cultures using a defined medium containing glucose and/or starch as the carbohydrate source. The batch culture studies reveal that reduced availability of arginine hampers growth of recombinant cells (which lack an arginine synthesis gene) but promotes production of α-amylase and substitution of glucose by starch as the carbohydrate source leads to slower growth of recombinant cells and increased production of α-amylase per unit cell mass. Retention of recombinant cells over prolonged periods in continuous cultures is not possible without continuous application of antibiotic selection pressure owing to segregational plasmid instability. Fed-batch experiments with constant volumetric feed rate demonstrate that α-amylase production is enhanced at lower feed concentration of starch (sole carbohydrate source) and lower volumetric feed rate. Such slow addition of starch is however not conducive for growth of recombinant cells. The expression of the thermostable α-amylase gene carried on the recombinant plasmid pAT5 (derived from a plasmid isolated from a thermophilic bacterium) is promoted at higher temperatures, while growth of recombinant cells is depressed. In all batch and fed-batch experiments, production of α-amylase is observed to be inversely related to growth of recombinant cells. The efficacy of two-stage bioreactor operations, with growth of recombinant cells being promoted in the first stage and α-amylase production in the second stage, in attaining increased bulk α-amylase activity is demonstrated. © 1993 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260421003
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    Self-cycling fermentation in a stirred tank reactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1175-1180 
    Details
    ISSN: 0006-3592
    Keywords: self-cycling fermentation ; secondary metabolite ; biosurfactant ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Self-cycling fermentations (SCFs) were conducted in a stirred tank apparatus using Bacillus subtilis and Acinetobacter calcoaceticus. The systems were very stable and the experiments lasted through many cycles. The variation of parameters such as biomass and doubling time from cycle to cycle was small. The stirred tank reactor (STR) allowed a much better control of the working volume in the fermentor from cycle to cycle, compared to the cyclone column, and it was not necessary to make periodic corrections.The production of surfactin from B. subtilis was achieved without extending the cycle time. The harvested broth at the end of each cycle was allowed to remain in a secondary vessel, at ambient temperature, before being collected. It is exhaustion of the limiting nutrient which causes an increase in dissolved oxygen (DO). At this point, the computer, which constantly monitors the DO, triggered the harvesting sequence to end the cycle. Thus, the mature culture in the secondary vessel experienced appropriate conditions for the production of the secondary metabolite. Meanwhile, the next batch of cells was being grown in the primary reactor.The response of a gas analyzer on the effluent paralleled that of the DO measurements in the fermentor. These data for oxygen and carbon dioxide exhibited less noise than the DO readings. Either would be a more reliable parameter for feedback control of the SCF because the problem of fouling of the DO probe after extended runs of many cycles would be eliminated. © 1993 John Wiley & Sons, Inc.
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    Affinity-based reversed micellar protein extraction: II. Effect of cosurfactant tail length (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1209-1217 
    Details
    ISSN: 0006-3592
    Keywords: reversed micelles ; protein extraction ; cosurfactant ; chymotrypsin ; affinity partitioning ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The selectivity of protein extraction by reversed micellar solutions can be improved by the addition of affinity cosurfactants bearing ligands which bind strongly to the target protein. The interactions between cosurfactant and protein, as well as the interfacial activity of both the free cosurfactant and the protein-cosurfactant complex, were accounted for in a model of the affinity-partitioning process. The aqueous phase dissociation constant was used to describe the protein-ligand interactions. The interfacial partition coefficient for several cosurfactant families varied with tail length according to the well-established hydrophobic effect. Control studies with alkylated chymotrypsin showed that when longer hydrophobic tails are irreversibly attached to the protein, the protein partitions more strongly to the reversed micellar phase. In contrast, for reversible protein-cosurfactant binding, the model predicts a maximum in protein uptake when the cosurfactant tail length is varied; the decrease at longer tail lengths is due to the lowered aqueous phase concentration of affinity cosurfactant, resulting in the formation of fewer protein-cosurfactant complexes. This behavior was confirmed experimentally. © 1993 John Wiley & Sons, Inc.
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    Masthead (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260421101
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    Study on separation of conalbumin and lysozyme from high concentration fresh egg white at high flow rates by a novel ion-exchanger (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1086-1090 
    Details
    ISSN: 0006-3592
    Keywords: ion-exchanger ; conalbumin ; lysozyme ; egg-white ; separation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this report, we show that it is possible to separate valuable proteins from egg-white using a ProductivTM CM ion-exchanger column operated at flow rates significantly higher than those than can be achieved using traditional particulate adsorbents. In the approach taken, sample pretreatment is restricted to a simple dilution of the egg-white, which can then be applied to the column at superficial velocities (Vs) of up to 13.8 m/h. Under a loading of 220 mg total protein per milliliter of ion-exchanger, the resolution (Rs) between the eluted conalbumin and lysozyme fractions was found to be almost constant during nine consecutive adsorption/desorption cycles. For all nine consecutive batches, the column average adsorption capacity was greater than 30 mg/mL, with 90% recovery of adsorbed protein being achieved in each run. The overall productivity achieved was 12.6 kg/m3 h for lysozyme and 31.2 kg/m3 h for conalbumin. © 1993 John Wiley & Sons, Inc.
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    Response to comments on “in search of a thermodynamic description of biomass yields for the chemotropic growth of microorganisms” (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1127-1130 
    Details
    ISSN: 0006-3592
    Keywords: thermodynamic efficiency ; dissipation ; Gibbs energy dissipation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is shown that for the thermodynamic description of microbial growth there does not exist complete equivalency between the “efficiency” and “Gibbs energy dissipation” approach. The reasons for this absence of equivalency are discussed, and it is argued that the “dissipation approach” has much more favorable properties compared with the efficiency approach. © 1993 John Wiley & Sons, Inc.
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    Stability of antibody productivity is improved when hybridoma cells are entrapped in calcium alginate beads (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1131-1135 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; instability ; immobilization ; monoclonal antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Loss of monoclonal antibody (MAb) productivity in long-term, free-suspended cell culture is often attributed to the appearance of a nonproducing population of hybridoma cell (NP) in the culture which has a growth advantage over the producing population (P). However, when an NP appears in long-term culture of entrapped cells, it may not be able to take over the whole culture in a short period of time due to the limited growth of the entrapped cells. In order to examine the hypothesis that entrapped cells can have improved stability of MAb productivity due to limited cell growth, free-suspended cell culture and calcium alginate-entrapped cell culture with inocula consisting of a P and an NP were compared with regard to stability of MAb productivity in a repeated fed-batch culture. In free-suspended cell culture, the NP appeared to take over the whole culture within three batches, and thereby MAb production completely disappeared. In entrapped cell culture, an NP appeared to outgrow the P rapidly only during an exponential growth phase, resulting in a significant decrease in specific MAb productivity, qMAb, from 11.58 μg/106 cell/day to 2.76 μg/106 cell/day. However, when the cell growth was limited in entrapped cell culture, the NP no longer outgrew the P rapidly, as indicated by the stable value of qMAb. In addition, when the cells recovered from the alginate beads by citrate buffer treatment were subcultured in free-suspended cell culture, MAb production rapidly deteriorated and completely disappeared within two batches. Thus, the P present at a small fraction of viable cell concentration in the beginning of the free-suspended cell culture, which were previously entrapped in alginate beads, seemed to be outgrown rapidly by the NP. Taken together, the results obtained from these experiments support the hypothesis that the limited cell growth in entrapped cell culture, which keeps an NP from taking over the whole culture, is responsible, in part, for the improved stability of MAb productivity. © 1993 John Wiley & Sons, Inc.
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    Membrane formation by interfacial cross-linking of chitosan for microencapsulation of Lactococcus lactis (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1157-1163 
    Details
    ISSN: 0006-3592
    Keywords: chitosan microcapsules ; lactic acid bacteria ; microencapsulation ; interfacial cross-linking ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lactic acid bacteria were microencapsulated within cross-linked chitosan membranes formed by emulsification/interfacial polymerization. The technique was modified and optimized to provide biocompatible conditions during encapsulation involving the use of mineral oils as the continuous phase and chitosan as the membrane material. Chitosan cross-linked with hexamethylene diisocyanate or glutaraldehyde resulted in strong membranes, with a narrow size distribution about a mean diameter of 150 μm. Cell viability and activity was demonstrated by the acidification of milk. Loss of acidification activity during microencapsulation was recovered in subsequent fermentations to levels similar to that of free cell fermentations. © 1993 John Wiley & Sons, Inc.
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    Real-Time compensation of the inner filter effect in high-density bioluminescent cultures (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1190-1198 
    Details
    ISSN: 0006-3592
    Keywords: fermentation ; bioprocess monitoring ; bioluminescence ; inner filter effect ; Escherichia coli ; cell concentration monitoring ; fiber optic ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bioluminescence has recently become a popular research tool in several fields, including medicine, pharmacology, biochemistry, bioprocessing, and environmental engineering. Beginning with purely qualitative goals, scientists are now targeting more demanding applications where accurate, quantitative interpretation of bioluminescence is necessary. Using the recent advances in fiber-optic technology, bioluminescence is easily monitored in vivo and in real time. However, the convenience of this measurement is often concealing an unsuspected problem: the bioluminescence signal might be corrupted by a large error caused by the extinction of light by biological cells. Since bioluminescent cultures not only emit light but also absorb and scatter it, the measured signal is related in a complex, nonlinear, and cell-concentration-dependent manner to the “true” bioluminescence. This light extinction effect, known as the “inner filter effect,” is significant in high-density cultures. Adequate interpretation of the bioluminescence signal can be difficult without its correction. Here, we propose a real-time algorithm for elimination of the inner filter effect in a bioreactor. The algorithm yields the bioluminescence which would be measured if the glowing culture was completely transparent. This technique has been successfully applied to batch and continuous cultivation of recombinant bioluminescent Escherichia coli. © 1993 John Wiley & Sons, Inc.
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    Repeated fed-batch culture of hybridoma cells in nutrient-fortified high-density medium (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1229-1237 
    Details
    ISSN: 0006-3592
    Keywords: repeated fed-batch culture ; nutrient fortifications ; high-density culture ; hybridoma ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Long-term high-density cultivation of the hybridoma 2c3.1 was successfully carried out in a repeated fed-batch mode using high-density media that were constructed to meet in vitro cell growth limitations. The high-density culture was possible in a range of 0.5 ∼ 1.0 × 107 cells/mL in MBRI 40-02 medium for over 2500 h by the repeated supplementation of the most fortified medium, MBRI 40-03, and consequently, distinct enhancement of MAb production was achieved. MAb concentrations were maintained around 1 g/L for about 1000 h of the process and the maximum MAb concentration was around 1.56 g/L. The result supported strongly the fact that the nutritional fortification was the most critical factor for high-density cell culture in vitro. The mean chromosome number of the hybridoma 2c3.1 was maintained stably for about 1500 h, whereas gradual loss of the MAb activity was apparent during the long-term cultivation. © 1993 John Wiley & Sons, Inc.
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    Estimation of melting curves from enzymatic activity-temperature profiles (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1245-1251 
    Details
    ISSN: 0006-3592
    Keywords: enzyme denaturation ; thermal unfolding ; melting curve ; activity-temperature profile ; β-galactosidase ; hydrogenase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Measuring the reversible thermal unfolding of enzymes is valuable for quantifying the effects of environmental factors on the thermodynamic stability of proteins. The thermal unfolding behavior of enzymes is typically studied using calorimetry or optical techniques such as circular dichroism, fluorescence, or light scattering. These techniques often have practical limitations and usually require the protein to be electrophoretically pure. An alternative technique for analyzing the thermodynamic stability of enzymes is to estimate the melting curve from temperature-activity data. This technique does not require electrophoretically pure enzyme, provided the sample does not have competing enzymatic activities or proteins which can affect enzyme stability (e.g., proteases). Moreover, small amounts of contaminant proteins should not affect the results as long as enzymatic assays are performed at low protein concentrations where nonspecific protein-protein interactions are negligible. To illustrate this technique, the melting curve for β-galactosidase from Escherichia coli in the presence of 1 mM EDTA, and the shift caused by adding 1 mM Mg+2, were calculated from activity-temperature data. Melting temperatures predicted from activity-temperature data compared closely with those obtained using other techniques. Application of this analysis to multisubstrate enzymes is illustrated by estimating the melting profiles for partially purified hydrogenases from several thermophilic Methanococcii. Limitations and important considerations for estimating melting profiles from activity-temperature data are discussed. © 1993 John Wiley & Sons, Inc.
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    Adsorption-desorption of recombinant hepatitis B surface antigen (r-HBsAg) from P. pastoris on a diatomaceous earth matrix: Optimization of parameters for purification (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1238-1244 
    Details
    ISSN: 0006-3592
    Keywords: adsorption-desorption ; purification ; recombinant HBsAg ; hepatitis B surface antigen ; P. pastoris ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant hepatitis B surface antigen (r-HBsAg) produced in yeast is adsorbed on a diatomaceous earth matrix for purification purposes. A pH dependence in the adsorption-elution behavior was found. The capacity of celite (Hyflo Super Cei) for adsorbing r-HBsAg increased with decreasing pH. Nonspecific proteins were also adsorbed, but a low pH dependence was found. Elution from the matrix was performed using a basic pH buffer, in which r-HBsAg is more specifically adsorbed/desorbed than contaminant proteins, permitting the purification of the r-HBsAg. A pH of 4.0 was used for adsorption and pH 8.2 was used for desorption. The described protocol allows a purification factor between three- and fivefold with respect to contaminant proteins and sixfold with respect to contaminant DNA. Finally, the adsorption step was successfully scaled-up for production purposes. © 1993 John Wiley & Sons, Inc.
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    Design of a biomedical reactor for plasma low-density lipoprotein removal (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1252-1262 
    Details
    ISSN: 0006-3592
    Keywords: biomedical reactor ; extracorporeal circuit ; hypercholesteremia New Zealand white rabbits ; immobilized phospholipase A2 ; plasma separator reactor (PSR) ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The purpose of this study was to design a biomedical reactor that reduces plasma cholesterol when incorporated in an in vivo extracorporeal system. Phospholipase A2, immobilized onto Agarose beads and housed inside the bioreactor, modifies plasma low density lipoprotein (LDL) into a form that is rapidly removed from circulation. In a packed bed reactor, the enzymatic conversion of LDL to the modified form (with plasma taken from hypercholesterolemic New Zealand white rabbits) was relatively low, 25% ± 6 for a single pass of plasma through the reactor. An extended bed reactor, a hybrid of fluidized and packed bed reactors, was then developed to increase the conversion. This reactor displays a single pass conversion of 60% ± 5 under optimal flow conditions. An evaluation of the flow rate through the reactor indicates that the system is limited by external mass transfer when employed under in vivo conditions. In addition, this system requires blood separation before the enzyme modification, which complicates the circuit control. Therefore, a new system was designed for in vivo use with rabbits. The resulting design, called the plasma separator reactor (PSR), combines plasma separation and enzymatic conversion in a single chamber. The PSR has three advantages over other studied systems: improved external mass transfer conditions, easy controlability, and simple set-up procedures. Single pass conversion reached 52% ± 12 in suboptimal flow under simulated in vivo conditions. This reactor was also tested in vivo with hypercholesterolemic New Zealand white rabbits. A continuous conversion of up to 80% ± 6 of rabbit plasma phospholipids was observed during 90 min of blood circulation (5 mL/min). The decrease in total plasma cholesterol reached a level of 60% of the initial value and was observed to be a function of the bioreactor enzyme activity. © 1993 John Wiley & Sons, Inc.
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    Multigradient method for optimization of slow biotechnological processes (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1301-1310 
    Details
    ISSN: 0006-3592
    Keywords: Optimization ; multigradient search ; xylitol conversion ; Candida guilliermondii ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method (named a “jumping spider”) is introduced for the optimization of slow biotechnological processes. The more traditional sequential experimentation (i.e., gradient search, simplex, etc.) is not well suited for slow dynamic processes, e.g., plant cell culture and differentiation. Therefore, a more simultaneous approach is proposed. A large number of initial experiments are performed, on the basis of which several of the initial experiments are selected as starting points. A search is then performed simultaneously from several gradient directions and the optimum is estimated by a quadratic approximation. In simulations, the spider generally climbs up the slopes quickly and the final estimator yields good maximum point estimates even on a complex topography. The spider may even approach more than one local maximum point simultaneously. As a model application, the average xylitol conversion rate of Candida guilliermondii was optimized in relation to cultivation volume (oxygen availability) and the concentration of nitrogen and phosphorus in the medium. A threefold increase in xylitol production was obtained with three experimental steps. © 1993 John Wiley & Sons, Inc.
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    Production of cellobiose by enzymatic hydrolysis: Removal of β-glucosidase from cellulase by affinity precipitation using chitosan (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 405-410 
    Details
    ISSN: 0006-3592
    Keywords: affinity precipitation ; β-glucosidase ; cellobiose production ; cellulase ; chitosan ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Removal of β-glucosidase (BG) from cellulase is essential to the enzymatic production of cellobiose from cellulose because of the high reactivity of BG with cellobiose to form glucose. Chitosan is a reversibly soluble-insoluble polymer depending on pH, and it has an affinity with the other components, endo-β-1,4-glucanase and cellobiohydrolase, or cellulase. The affinity precipitation technique using chitosan is an effective way to fractionate cellulase for the above purpose. Hydrolysis experiments of cellulose with the residual fractionated enzyme gave higher cellobiose contents in the soluble sugar products. © 1993 John Wiley & Sons, Inc.
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    Instability caused by high strength of cheese whey in a UASB reactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 700-706 
    Details
    ISSN: 0006-3592
    Keywords: anaerobic digestion ; cheese whey ; UASB reactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The anaerobic digestion of cheese whey was studied in a UASB reactor. The profiles of the reactor, i.e., the distributions of the substrate concentration and pH under different operating conditions were developed. From the concentrations of substrates measured at various levels above the bottom of the reactor, two reaction stages, namely acidogenesis and methanogenesis, were distinguished. The instability caused by high influent concentration was interpreted as the accumulation of VFAs in the acidogenic stage beyond the assimilative capacity of the methanogenic stage. A range of stable operating conditions was predicted from the results of the profile measurements. The optimal influent concentration was found to be between 25 and 30 g COD/L at an HRT of 5 days for system stability. Other options fro stability control were discussed. © 1993 John Wiley & Sons, Inc.
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    A statistical analysis of the effect of substrate utilization and shear stress on the kinetics of biofilm detachment (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 728-735 
    Details
    ISSN: 0006-3592
    Keywords: biofilm ; shear stress ; substrate loading ; biofilm detachment ; Pseudomonas aeruginosa ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: One of the least understood processes affecting biofilm accumulation is detachment. Detachment is the removal of cells and cell products from an established biofilm and subsequent entrainment in the bulk liquid. The goal of this research was to determine the effects of shear stress and substrate loading rate on the rate of biofilm detachment.Monopopulation Pseudomonas aeruginosa and undefined mixed population biofilms were grown on glucose in a RotoTorque biofilm reactor. Three levels of shear stress and substrate loading rate were used to determine their effects on the rate of detachment. Suspended cell concentrations were monitored to determine detachment rates, while other variables were measured to determine their influence on the detachment rate. Results indicate that detachment rate is directly related to biofilm growth rate and that factors which limit growth rate will also limit detachment rate. No significant influence of shear on detachment rate was observed.A new kinetic expression that incorporates substrate utilization rate, yield, and biofilm thickness was compared to published detachment expressions and gives a better correlation of data obtained both in this research and from previous research projects, for both mono- and mixed-population biofilms. © John Wiley & Sons, Inc.
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    Masthead (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993) 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    URL: http://dx.doi.org/10.1002/bit.260410801
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    Enhancement of cloned gene product synthesis via autoselection in recombinant Saccharomyces cerevisiae (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 801-810 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; autoselection ; plasmid stability ; cloned gene expression ; medium enrichment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Saccharomyces cerevisiae autoselection strains with mutations in the ura3, fur1, and urid-k genes have been obtained through a sequential isolation procedure. This autoselection system is an extension of one described by Loison et al. The mutations effectively block both the pyrimidine biosynthetic and salvage pathways and in combination are lethal to the host. Therefore, a plasmidencoded URA3 gene is essential for cell viability regardless of the growth conditions, and complex (traditionally nonselective) media can be employed without the risk of plasmid loss. The effects of medium enrichment on growth and cloned gene product synthesis were examined in batch culture for two autoselection strains. The plasmid gene product β-galactosidase was under the control of the yeast GAL1 promoter, and two methods of induction were employed; one strain was induced via temperature shift while the other was induced by galactose addition. Three nutrient media were investigated: a lean selective medium (SD), a richer semidefined medium (SDC), and a rich complex medium (YPD). The results demonstrated the improvements in cloned gene productivity possible when the growth medium is enriched, with up to 10-fold increases in β-galactosidase productivity observed. Plasmid instability and mutation reversion were not problems for the autoselection strains, even in uracil-containing medium. Short-term plasmid stabilities were approximately 90% in all three media tested. During continuous culture of the autoselection temperature-sensitive strain, long-term plasmid stability was excellent and β-galactosidase expression remained high after more than 25 residence times under inducing conditions. In contrast, both β-galactosidase specific activity and plasmid stability decreased linearly with time for an analogous nonautoselection strain. The introduced fur1 and uridk mutations were very stable; after more than 50 generations of growth in complex medium, stability values of 99-100% were measured. © 1993 Wiley & Sons, Inc.
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    Computation of pH evolution versus ionic products concentration in a fermentation broth (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 830-832 
    Details
    ISSN: 0006-3592
    Keywords: ionic equilibrium ; pH computation ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An algorithm developed for pH computation has been tested to calculate the theoretical pH changes in a culture medium during the course of a fermentation. A divergence between the computed pH value and the value measured with the electrode allows us to highlight the presence of undetected ionic products. The calculation with the algorithm by means of a computer requires only the knowledge of the ionic properties of the substrates and detected products and existing thermodynamic constants. © 1993 Wiley & Sons, Inc.
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    Homogeneous immunoassay of polyclonal antibodies by use of antigen-coupled liposomes (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 862-867 
    Details
    ISSN: 0006-3592
    Keywords: homogenous immunoassay ; polyclonal antibody ; lysis of liposome ; complement system ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anti-cytochrome c and anti-myoglobin antibodies were assayed by use of immunoliposomes coupled with the antigens. Addition of complement under the existence of the antigens. Addition of complement under the existence of the antigen-antibody complex on the surface of the liposome caused lysis of the liposomes, which was proportional to the amount of the antigen-antibody complex formed as well as the concentration of complement added. Thus, the degree of marker release depended on the average association constant and also on its heterogeneity of the polyclonal antibodies, which shows that the results assayed by this method are correlated to the antibody ability to form the antigen-antibody complex © 1993 Wiley & Sons, Inc.
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    Nutrient-split feeding strategy for dialysis cultivation of Escherichia coli (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 1092-1100 
    Details
    ISSN: 0006-3592
    Keywords: high cell density cultivation ; Escherichia coli ; XAD adsorbents ; dialysis reactor ; controlled substrate feed ; inhibitory products, removal of ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reduction in nutrient loss during dialysis cultivation of Escherichia coli on a glycerol medium was investigated. A dialysis reactor with an inner fermentation and an outer dialysis chamber was used. Aerobic condition was maintained by limiting the glycerol feed rate to an optimum value which was estimated from the oxygen requirements for glycerol oxidation and oxygen transfer capacity of the reactor. High reduction in nutrient loss was achieved by using water as the dialyzing fluid. However, osmotic movement of water from the dialysis to the fermentation chamber was observed, and the final cell concentration was low. With a nutrient-split feeding strategy (feeding glycerol directly to the fermentation chamber and dialyzing with salt solution), glycerol loss was small, there was no osmotic flux of water to the fermentation chamber, and the cell concentration was high. Both glycerol and salt loss could be avoided, and a cell concentration of 170 g/L was obtained when the dialysis process was substituted by addition of XAD adsorbents to the dialysis chamber. Application of this nutrient-split feeding strategy to cell cultivation in a stirred tank reactor, coupled with dialysis in external dialyzer modules, resulted in low cell concentrations. © 1993 Wiley & Sons, Inc.
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    Experimental determination of flux control distribution in biochemical systems: In vitro model to analyze transient metabolite concentrations (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 1121-1128 
    Details
    ISSN: 0006-3592
    Keywords: flux control coefficient ; metabolic control analysis ; enzyme kinetics ; glycolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Determination of the control coefficients allows the identification of rate-controlling steps in a reaction system. However, the measurement of the flux control coefficients in a biochemical system is not a trivial task, except for some special cases. We have developed a theoretical basis for the direct determination of these coefficients from dynamic responses. In order to show the validity of this methodology experimentally, the dynamic approach is applied to an in vitro reconstituted partial glycolytic pathway to determine the flux control coefficients of hexokinase and phosphofructokinase. It is shown that the dynamic approach gives consistent results, which agree well with values obtained by the direct enzyme titration method. The detailed procedure and potential applications to other systems, such as immobilized enzyme or cell reactors, are discussed. © 1993 Wiley & Sons, Inc.
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    Symmetric branching model for the kinetics of mycelial growth (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1-10 
    Details
    ISSN: 0006-3592
    Keywords: mycelial kinetics ; symmetric branching tree ; microscopic parameters ; macroscopic parameters ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model, linking microscopic to macroscopic parameters of the kinetics of mycelial growth is presented. The model consists of two parts: (a) a microscopic description, based on the assumption that growth of a mycelium can be represented approximately by the growth of a symmetric binary tree, where the branching level (microscopic state variable) is logarithmically related to the number of tips and segments; and (b) a macroscopic description which makes use of the microscopic description in order to define the parameters related to the evolution of biomass (macroscopic state variable) as a function of time. The latter uses a distribution of arrested tips in a population of mycelia, in order to estimate the fraction of non-growing biomass in terms of a power law function with coefficient, n, of the biomass concentration. The microscopic description explains the fact that the germ tube specific growth rate of Aspergillus nidulans measured in a growth chamber, is about the double the specific growth rate of this organism, when measured in shake flasks. It predicts that the length of the hyphal growth unit of the mycelium of Geotrichum candidum would be approximately the double the germ tube length measured at the time just before the first branching event. It also allows the derivation of useful expressions for predicting macroscopic parameters, such as the maximal specific growth rate, the initial amount of biomass, and the amount of biomass before the branching process starts. Those estimates are done in terms of microscopic quantities, i.e., the amount of germinated spores, the diameters of the spores and hyphae, the average rate of tip extension, and the average internodal segment length. Estimation of coefficient n by fitting the macroscopic description to a growth curve of A. niger gives an indication on the degree of skewness of the distribution of arrested mycelia. Estimated macroscopic parameters are in relative good agreement with measured average segment length. © 1993 John Wiley & Sons, Inc.
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    Transport and intracellular accumulation of acetaldehyde in saccharomyces cerevisiae (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 24-29 
    Details
    ISSN: 0006-3592
    Keywords: acetaldehyde ; intracellular accumulation ; inhibition ; transport ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rate of acetaldehyde efflux from yeast cells and its intracellular concentration were studied in the light of recent suggestions that acetaldehyde inhibition may be an important factor in yeast ethanol fermentations. When the medium surrounding cells containing ethanol and acetaldehyde was suddenly diluted, the rate of efflux of acetaldehyde was slow relative to the rate of ethanol efflux, suggesting that acetaldehyde, unlike ethanol, may accumulate intracellularly. Intracellular acetaldehyde concentrations were measured during high cell density fermentations, using direct injection gas chromatography to avoid the need to concentrate or disrupt the cells. Intracellular acetaldehyde concentrations substantially exceeded the extracellular concentrations throughout fermentation and were generally much higher than the acetaldehyde concentrations normally recorded in the culture broth in ethanol fermentations. The technique used was sensitive to the time taken to cool and freeze the samples. Measured intracellular acetaldehyde concentrations fell rapidly as the time taken to freeze the suspensions was extended beyond 2 s. The results add weight to recent claims that acetaldehyde toxicity is responsible for some of the effects previously ascribed to ethanol in alcohol fermentations, especially Zymomonas fermentations. Further work is required to confirm the importance of acetaldehyde toxicity under other culture conditions. © 1993 John Wiley & Sons, Inc.
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    Construction, expression, and analysis of recombinant HIV gp41 constructs containing a novel cellular binding domain (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 81-86 
    Details
    ISSN: 0006-3592
    Keywords: human immunodeficiency virus ; gp41 ; recombinant fusion protein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The gp41 polypeptide of human immunodeficiency virus (HIV) contains an immunosuppressive domain, an epitope which elicits specific cytolytic T cell responses to HIV, and a complement Clq interactive domain. In addition, a synthetic peptide called CS3, derived from gp41 (amino acids 576-593 of gp160) and contiguous with the major immunodominant domain, binds to cellular proteins and may be important in HIV entry/fusion. In order to further investigate the role of the CS3 region of gp41 in cellular binding and to investigate other properties of gp41, sufficient quantities of this polypeptide must be readily available. We have therefore cloned the region of the HIV genome between nucleotides 7891 and 8188 (corresponding to amino acids 541-639 of gp160) into a series of procaryotic expression vectors. The resulting clones express a recombinant polypeptide of gp41 (r41). Two of these recombinants, pMAL-cRl/r41 and pGEMEX-2/r41, expressed the highest and most consistent levels of r41 as judged by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. With the pMAL-cRl/r41 construct, r41 was expressed as a fusion to the maltose-binding protein (MBP) and, following purification by affinity chromatography, was cleaved from MBP by factor Xa protease digestion. MBP/r41 may be useful for studies of a reported gp41 cellular binding domain and may facilitate studies involving other functions ascribed to this region of gp41. © 1993 John Wiley & Sons, Inc.
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    Comparison of soluble and immobilized trypsin kinetics: Implications for peptide synthesis (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 118-124 
    Details
    ISSN: 0006-3592
    Keywords: trypsin kinetics ; peptide synthesis ; enzyme immobilization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The protease trypsin was immobilized to porous glass in both the presence and absence of acetylated soybean trypsin inhibitor (STI) to determine whether immobilization could alter enzyme activity in favor of aminolysis over hydrolysis. Actiive-site titration with 4-methylumbelliferylguanidinobenzoate (MUGB) showed that only about 10% of immobilized trypsin had catalytic activity. Immobilization in the presence of STI produced a higher yield of active enzyme accessible to the inhibitor but did not increase the total yield of MUGB-active immobilized enzyme. Thus, enzyme inactivation upon immobilization could not be attributed to an inaccessible enzyme orientation, nor did STI prevent inactivation by stabilizing the active-site conformation. Kinetic parameters were determined for soluble and immobilized trypsin for two esters, N-tosyl-L-arginine methyl ester (TAME) and N-benzoyl-L-arginine ethyl ester (BAEE), and two amides, N-benzoyl-L-arginine p-nitroanilide (BAPNA) and N-t-boc-leucylglycylarginine p-nitroanilide (LGRNA). In all cases, immobilization caused a greater decrease in kcat for amidase activity than for esterase activity. The ratio [kcat/ Km (ester)]/[kcat/Km (amide)] increased slightly or stayed the same (for I.GRNA) or decreased sharply (for BAPNA). Including STI during immobilization had little effect on the active enzyme's intrinsic kinetics. A direct comparison of energy diagrams and free energies of activation for BAEE and BAPNA indicates that immobilization raises the free energy barriers for both amide and ester hydrolysis and lowers the energy barrier for aminolysis. In practice, these effects should lower the amidase activity and increase the aminolysis-hydrolysis ratio, rendering the immobilized enzyme a more efficient catalyst for peptide synthesis. © 1993 John Wiley & Sons, Inc.
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    Improved protein synthesis and secretion through medium enrichment in a stable recombinant yeast strain (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 95-102 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; secretion ; MFα1 ; autoselection ; plasmid stability ; medium enrichment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two Saccharomyces cerevisiae strains were employed to investigate the effects of medium enrichment on the expression and secretion of a recombinant protein. One was a stable autoselection strain with mutations in the ura3, fur1, and urid-k genes. The combination of these three mutations blocks both the pyrimidine nucleotide biosynthetic and salvage pathways and is lethal to the cells. Retention of the plasmid, which carries a URA3 gene, was essential for cell viability. Therefore, all media were selective, allowing cultivation of the strain in complex medium. The second strain was a nonautoselection (control) strain and is isogenic to the first except for the fur1 and urid-k mutations. The plasmid utilized contains the yeast invertase gene under the control of the MFα1 promoter and leader sequence. The expression and secretion of invertase for the autoselection strain were examined in batch culture for three media: a minimal medium (SD), a semidefined medium (SDC), and a rich complex medium (YPD). Biomass yields and invertase productivity (volumetric activity) increased with the complexity of the medium; total invertase volumetric activity in YPD was 100% higher than in SDC and 180% higher than in SD. Specific activity, however, was lowest in the SDC medium. Secretion efficiency was extremely high in all three media; for the majority of the culture, 80-90% of the invertase was secreted into the periplasmic space and/or culture medium. A glucose pulse at the end of batch culture in YPD facilitated the transport of residual cytoplasmic invertase. For the nonautoselection strain, invertase productivity did not improve as the medium was enriched from SDC to YPD, and plasmid stability in the complex YPD medium dropped from 54% to 34% during one batch fermentation. During long-term sequential batch culture in YPD, invertase activity decreased by 90% and the plasmid-containing fraction dropped from 56% to 8.8% over 44 generations of growth. The expression level for the autoselection strain, however, remained high and constant over this time period, and no reversion at the fur1 or urid-k locus was observed. © 1993 John Wiley & Sons, Inc.
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    A synergistic kinetics model for enzymatic cellulose hydrolysis compared to degree-of-synergism experimental results (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 145-148 
    Details
    ISSN: 0006-3592
    Keywords: synergy ; heterogeneous enzyme kinetics ; cellulose hydrolysis kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is demonstrated that a two-enzyme component synergistic model can account for the observation that the degree of synergism goes through a maximum as the total enzyme concentration is increased. The degree of synergism is low at low enzyme concentration because the extent of conversion is low and therefore the cellulose chain ends, present originally, are not exhausted; thus the action of the cellobiohydrolase (CBH) is not dependent on the chain ends generated by the endoglucanase (EG). The degree of synergism declines at high enzyme concentration due to saturation of adsorption sites with CBH, thus decreasing the generation of chain ends by EG. © 1993 John Wiley & Sons, Inc.
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    Effect of operating conditions on solid substrate fermentation (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 149-158 
    Details
    ISSN: 0006-3592
    Keywords: solid substrate fermentation ; evaporative cooling ; optimum temperature ; humidity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this work the effects of environmental parameters on the performance of solid substrate fermentation (SSF) for protein production are studied. These parameters are (i) air flow rate, (ii) inlet air relative humidity, (iii) inlet air temperature, and (iv) the heat transfer coefficient between the outer wall of the fermentor and the air in the incubator. The air flow is supplied to effect cooling of the fermented mass by evaporation of water. A dynamic model is developed, which permits estimation of biomass content, total dry matter, moisture content, and temperature of the fermented matter. The model includes the effects of temperature and moisture content on both the maximum specific growth rate and the maximum attainable biomass content. The results of the simulation are compared with actual experimental data and show good agreement with them. The most important conclusions are that (i) the evaporative cooling of the biomass is very effective for temperature control and (ii) the air flow rate and the heat transfer coefficient have strong effects but they affect the biomass morphology and are not controllable easily. Also, a simple technique for the determination of the optimum temperature and moisture content profile for cell protein production is applied. The simulated biomass production increases considerably employing the optimum temperature and moisture content profiles. The ultimate goal is to implement the determined effects of the environmental parameters on the SSF biomass production and the temperature and moisture variation profiles to effectively control the SSF and optimize the biomass production. © 1993 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260420202
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    Cell retention-chemostat studies of hybridoma cells - analysis of hybridoma growth and metabolism in continuous suspension culture in serum-free medium (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 185-195 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma metabolism ; perfusion culture ; suspension culture ; cell retention ; antibody productivity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The steady-state metabolic parameters for a hybridoma cell line have been determined in continuous suspension-perfusion culture over a wide range of perfusion rates and cell bleed rates. Significant increases in viable cell concentrations and volumetric productivities were achieved at high perfusion rates and low cell bleed rates. At the low growth rates examined in this study, cellular metabolism shifted to become more oxidative, and as a result, the fraction of consumed substrate converted to inhibitory metabolic by-products was reduced. Specific antibody productivity was found to be non-growth associated. © 1993 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260420206
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    Are water-immiscibility and apolarity of the solvent relevant to enzyme efficiency? (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 390-393 
    Details
    ISSN: 0006-3592
    Keywords: organic solvents ; enzyme catalysis ; immiscibility with water ; hydrophobicity of solvents ; dipole moment dielectric constant ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The question of whether the solvent's water-immiscibility is relevant to enzymatic activity was addressed by assaying four different hydrolases (three lipases and one protease) in nine anhydrous solvents of similar hydrophobicities of which four were infinitely miscible with water and five were not. For no enzyme was a jump in activity observed upon a transition from water-miscible to water-immiscible solvent. The relevance of solvent apolarity to enzymatic efficiency was also examined. To this end, three groups of isomeric anhydrous solvents were selected where within each group of isomeric anhydrous solvents were selected where within each group one solvent was apolar (i.e., lacked a permanent dipole moment). For none of the four enzymes studied was activity significantly higher in apolar solvents than in their polar counterparts. Thus we conclude that often-cited solvent's immiscibility with water and apolarity by themselves are irrelevant to enzymatic activity. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410314
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    Calculation of entropy change accompanying growth of Escherichia coli K-12 on succinic acid (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 422-428 
    Details
    ISSN: 0006-3592
    Keywords: entropy of growth ; Escherichia coli K-12 ; entropy of anabolism ; entropy change ; entropy of formation ; entropy of formation of cells ; cellular entropy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ΔSf′ of one unit carbon formula weight of Escherichia coli K-12 cells, when grown on succinic acid, was calculated to be -80.13 J/deg. This value could then be used to calculate the entropy change accompanying the anabolism and metabolism of succinic acid to be 30.82 J/deg and 32.40 J/mol deg, respectively. The entropy of one unit carbon formula weight of dried E. Coli K-12 cells is calculated to be 94.40 J/deg, which when divided by the mass of these cells becomes 3.90 J/g deg. The corresponding entropy of succinic acid is 2.77 J/g deg, making it apparent that the entropy per unit mass of the cells is greater than that of the substrate. It might be thought that because the cells appear to be so much more complex than the substrate, the cells should have a lesser entropy per unit mass than the substrate. That this does not appear to be true leads to the conclusion that the macromolecular organization (informational content?) of the cells contributes only in a very minor way to the total physical entropy of cells. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/bit.260410405
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    Analysis of substrate protection of an immobilized glucose isomerase reactor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 451-458 
    Details
    ISSN: 0006-3592
    Keywords: immobilized glucose isomerase ; substrate protection ; reactor analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of substrate protection on enzyme deactivation was studied in a differential bed and a packed bed reactor using a commercial immobilized glucose isomerase (Swetase, Nagase Co.). Experimental data obtained from differential bed reactor were analyzed based on Briggs-Haldane kinetics in which enzyme deactivation accompanying the protection of substrate was considered. The deactivation constant of the enzyme-substrate complex was found to be about half of that of the free enzyme. The mathematical analysis describing the performance of a packed bed reactor under the considerations of the effects of substrate protection, diffusion resistance, and enzyme deactivation was studied. The system equations for the packed bed reactor were solved using an orthogonal collocation method. The presence of substrate protection and the diffusion effect within the enzyme particles resulted in an axial variation of effectiveness factor, ηD, along the length of the packed bed. The axial distribution profile of ηD was found to be dependent on the operation temperature, Based on the effect of substrate protection, a better substrate feed policy could be theoretically found for promoting productivity in long-term operation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410408
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    Reverse micelles in protein separation: The use of silica for the back-transfer process (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 489-492 
    Details
    ISSN: 0006-3592
    Keywords: reverse micelles ; back-extraction ; silica ; proteins ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to use reverse micellar solutions successfully for the separation of proteins, good methods are needed to recover the biomolecules into an aqueous environment after solubilization into organic micellar media. Usually the recovery is accomplished by equilibrating the protein-loaded reverse micellar solution with a water phase containing an appropriate salt (back-transfer). In this article we describe an alternative “back extraction” procedure which is based on the addition of silica to the protein-containing reverse micellar solution. In this way, the water is stripped from the reverse micellar solution. [i.e., bis(2-ethylhexyl) sodium sulfosuccinate (AOT)/isooctane/water] and the proteins adsorb to the silica particles. The adsorption process is shown to be practically quantitative. The subsequent recovery of the proteins form the silica into an aqueous solution turns out to be most efficient at alkaline pH (pH 8); 60-80 of the total protein (α-chymotrypsin or trypsin) could be recovered. The specific enzyme activity at the end of the whole cycle can be as high as 80-100%. The procedure is applied also for the back extraction from micellar solutions in which, instead of AOT, a biocompatible surfactant such as a synthetic short-chain lecithin was used. It is shown that the recovery of a α-chymotrypsin and trypsin is also achievable under these conditions in quite good yield and under good maintenance of the enzyme's catalytic activity. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410413
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    Production of the siderophore enterobactin: Use of four different fermentation systems and identification of the compound by HPLC (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 237-244 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli ; iron transport ; enterobactin HPLC ; dialysis membrane fermentor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The article describes four different fermentation procedures for Escherichia coli AN311, a producer of enterobactin. A regular rotary shaker culture with a biphasic system consisting of an agar layer (as a reservoir for feeding processes) and a layer of liquid medium, 2.4 L and 10 L batch cultures, and a novel dialysis membrane fermentor were used. With the use of this latter fermentor type, the production of enterobactin could be increased by a factor of about 9.5, while growth increased by a factor of 12 compared to the other systems. For the rapid and reliable quantification of the concentration and purity of enterobactin an analytical and preparative high-performance liquid chromatography (HPLC) method was established. The degradation compounds of this siderophore were detected by diodearray and bioassays. A comparison of total catechol production as well as the distribution between enterobactin and its degradation compounds is given. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410210
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    Continuous bioconversion of n-octane to octanoic acid by recombinant Escherichia coli (alk+) growing in a two-liquid-phase Chemostat (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 263-272 
    Details
    ISSN: 0006-3592
    Keywords: Continuous Culture ; two-liquid-phase system ; recombinant E. coli-alk system ; bioconversion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Escherichia coli is able to grow on sugars in the presence of a bulk n-alkane phase. When E. coli is equipped with the alk genes from Pseudomonas oleovorans, the resulting recombinant strain converts n-alkanes into the corresponding alkanoic acids. To study the effects of growth rate and exposure to a bulk apolar phase on the physiology and the productivity of E. coli, we have grown this microorganism in two-liquid-phase continuous cultures containing 5% (v/v) n-octane.In contrast to batch cultures of wild-tape E. coli grown in the presence of n-octane, cells remained viable during the entire continuous culture, which lasted 200 h. Bioconversion of n-octane to n-octanoic acid by a recombinant E. coli (alk+) in a two-liquid-phase continuous culture was made possible by optimizing both the recombinant host strain and the conditions of culturing the organism. Continuous production in such two-phase systems has been maintained for the least 125 h without any changes in the product concentration in the fermentation medium. The volumetric productivity was determined as a function of growth rate and showed a maximum at a dilution rate D = 0.32 h-1, reaching a continuous production rate of 0.5 g octanoate/L · h (4 tons/m3 · year). © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410213
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    Industrial separation of carboxylic and amino acids by liquid membranes: Applicability, process considerations, and potential advantage (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 287-295 
    Details
    ISSN: 0006-3592
    Keywords: carboxylic and amino acids ; supported ; emulsion ; hybrid liquid membranes ; facilitated transport ; uphill pumping ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260410302
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    Formation of microparticulate protein powder using a supercritical fluid antisolvent (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 341-346 
    Details
    ISSN: 0006-3592
    Keywords: gas antisolvent process ; protein powders ; supercritical fluids ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas antisolvent (GAS) expansion of dimethylsulfoxide (DMSO) and N,N-dimethylformamide (DMFA) solutions with supercritical carbon dioxide was used to produce biologically active powders of insulin. Powders with 90% of the particles smaller than 4 μm and 10% smaller than 1 μm were obtained under all conditions tested when the process was operated continuously, with small liquid droplets sprayed into a flowing supercritical continuum. Slow pressurization of the stagnant protein solution resulted in larger particles. In vivo tests on rats revealed no differences between the biological activity of processed and unprocessed insulin, GAS processing of organic solution appears to be a reliable and effective method for the production of dry, biologically active microparticulate powders of peptides and proteins. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410308
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    Measurement of hydrodynamic shear by using a dissolved oxygen probe (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 296-302 
    Details
    ISSN: 0006-3592
    Keywords: shear measurement ; cell culture reactors ; dissolved oxygen probe ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a dissolved oxygen (DO) probe is submerged in an air-saturated cell culture medium the thickness of the liquid film that exists outside the membrane of a DO probe changes with hydrodynamic shear. The response of the DO probe thus varies with the hydrodynamic shear environment near the DO probe in cell culture reactors. The thickness of the liquid film was estimated by using a three-layer model, which describes the flow of DO molecules through the liquid layer, the membrane, and the electrolyte, to the cathode of a DO probe. According to the three-layer model, the current output of the DO probe was a strong function of thickness of the liquid film outside the membrane of the DO probe. A correlation between shear rates on the surface of the probe and the DO saturation reading was obtained by using two concentric cylinders with a rotating inner cylinder. This correlation was then used to characterize the local hydrodynamic shear environment in a cell culture reactor. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410303
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