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  • Biochemistry and Biotechnology  (614)
  • 2020-2023
  • 1995-1999
  • 1990-1994  (614)
  • 1991  (614)
  • 1
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    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.260370101
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of carbon and oxygen limitations and calcium concentrations on biofilm removal processes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 17-25 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bacterial biofilm removal processes due to shear and catastrophic sloughing have been investigated in a turbulent flow system under conditions of carbon versus oxygen substrate limitations and varying aqueous phase calcium concentrations. Biofilm cellular and extracellular polymer carbon, total biofilm carbon and mass, and biofilm calcium concentrations are measured for pure culture biofilms of the facultative aerobe, Pseudomonas putida ATCC 11172. Results indicate oxygen-limited biofilms reach a higher steady-state biofilm organic carbon level than carbon-limited biofilms. Oxygen-limited biofilms also exhibit (1) a higher extracellular polymer-carbon: cell-carbon ratio throughout biofilm development and (2) a higher biofilm calcium content than carbon-limited biofilms. Increasing aqueous phase calcium concentrations increase the amount of biofilm calcium in both cases; the rate of calcium accumulation in oxygen-limited biofilms increases with increasing liquid phase calcium concentrations over the entire range studied while the rates of calcium accumulation in carbon-limited biofilms appear independent of aqueous phase calcium concentrations above 11.0 mg/L. Oxygen-limited biofilms with their higher extracellular polymer and calcium content exhibit shear removal rates that are 20-40% of those observed for carbon-limited biofilms. However, it is the oxygen-limited biofilms that experience catastrophic sloughing events. The carbon-limited biofilms studied here never sloughed even if subjected to intentional long-term deprivation of all nutrients. Reduced shear removal and the susceptibility to sloughing of the oxygen-limited biofilms are attributed to their more cohesive structure bought about by their relatively greater extracellular polymer production.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370105
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of an applied potential on the activity of carbonic anhydrase immobilized on graphite rods (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 491-496 
    Details
    ISSN: 0006-3592
    Keywords: potentiostatic control of enzyme activity ; immobilized enzyme ; graphite ; conducting support ; specific anion inhibition ; carbonic anhydrase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of both a positive and a negative applied potential on the p-NPA hydrolysis activity of bovine carbonic anhydrase (BCA) immobilized on graphite rods has been investigated. Background experiments show that the pH-activity profile for BCA free in solution is not affected by either a negative or a positive potential applied to graphite rods placed in the same solution. However, the activity of BCA immobilized by covalent attachment to a graphite rod is influenced by a potential externally applied to the graphite rod. An overall increase in activity (as determined by the initial rate of the p-NPA hydrolysis reaction) is observed in the presence of a -0.2 V (Ag/AgCl) applied potential, while decreased activity is evident at +0.6 V (Ag/AgCl). This is indicative of an electrolyte anion effect rather than a local pH effect. In the presence of the specific anion inhibitors Cl- and SCN-, the relative BCA activity increases at -0.2 V (Ag/AgCl) and decreases at +0.6 V (Ag/AgCl) are consistent with the different BCA inhibition constants for Cl- and SCN-. Accelerated loss of immobilized BCA activity also accompanies the application of the external potentials, particularly at +0.6 V (Ag/AgCl). Results described here represent an early example of potentiostatic control of nonredox enzyme activity. Several possible mechanisms are discussed including specific anion inhibition, enzyme surface charge/charged support material interactions, and charged product inhibition. It is likely that a combination of such mechanisms is operational in this system. The implications of external potentials affecting the activity of immobilized enzymes in the design of stable immobilized enzyme electrodes are also discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370511
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  • 4
    Electronic Resource
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    Growth and fermentation characteristics of new selected strains of Saccharomyces at high temperatures and high cell densities (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 528-536 
    Details
    ISSN: 0006-3592
    Keywords: yeast thermotolerance ; Saccharomyces ; invertase ; sugarcane juice fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Maintenance of high cell viability was the main characteristic of our new strains of thermotolerant Saccharomyces. Total sugar conversion to ethanol was observed for sugarcane juice fermentation at 38-40°C in less than 10 h and without continuous aeration of the culture. Invertase activity differed among the selected strains and increased during fermentation but was not dependent on cell viability. Invertase activity of the cells and optimum temperature for growth, as well as velocity of ethanol formation, were dependent on medium composition and the type of strain used. At high sugarcane syrup concentrations, the best temperature for ethanol formation by strain 781 was 35°C. Distinct differences among the velocities of ethanol production using selected strains were also observed in sugarcane syrup at 35-38°C.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370606
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  • 5
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    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.260370801
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  • 6
    Electronic Resource
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    Strategies for reducing solvent toxicity in extractive fermentations (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 716-722 
    Details
    ISSN: 0006-3592
    Keywords: κ-carrageenan matrix ; Lactobacillus delbrueckii ; toxicity ; solvent diffusion ; extractive fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The toxicity of an Alamine 336/oleyl-alcohol extraction system on Lactobacillus delbrueckii was investigated. It was shown that the solvent affected the cells through the water-soluble portion and the immiscible portion of the solvent. While immobilization significantly protected the cells from the immiscible solvent phase, the water-soluble part of the solvent still caused toxicity to the microorganisms due to diffusion of the solvent into the matrix. Adding soybean oil to the κ-carrageenan matrix could trap the diffusing solvent molecules, and therefore reduce the toxic effect from the water soluble portion of the solvent. The protective ability of soybean oil was quantified through mathematical modeling and experimentation.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370805
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  • 7
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    High-concentration cultivation of Lactococcus cremoris in a cell-recycle reactor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 746-754 
    Details
    ISSN: 0006-3592
    Keywords: Lactococcus cremoris ; cell-recycle fermentor ; cross-flow filtration ; high cell concentration cultures ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High-cell concentration cultivation of Lactococcus cremoris, a homofermentative lactic acid producer, in a cell-recycle fermentor is described. Cross-flow filtration allowing continuous removal of the inhibitory metabollte, the influence of dilution rate on growth was investigated in total or partial cell-recycle cultures. The dependence of growth characteristics on operating conditions was identified and quantified using lactose as the carbon source. Growth kinetics could be described by both lactate removal efficiency and nutrient availability. Based on physiological observations, biomass and lactic acid productivities were predicted in partial cell-recycle cultures.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370809
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  • 8
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    Observations of binary population biofilms (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 778-789 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biofilm research has focused on studies of undefined mixed microbial populations and, more recently, on investigations of monopopulation biofilms. In the first case, the biofilm is considered a homogeneous mass, ignoring the properties of individual species. The second case concentrates on the properties and processes of one microbial species in the biofilm. This article describes biofilm experiments conducted with monopopulations of Klebsiella pneumoniae and Pseudomonas aeruginosa and with binary populations of K. pneumoniae and P. aeruginosa. Process rates and stoichiometric coefficients were determined for the monopopulation and for the binary population biofilms and evaluated in light of the species distribution in the latter. Results indicate that neither the specific cellular product formation rate nor the glucose-oxygen stoichiometric ratio of K. pneumoniae or P. aeruginosa in the binary biofilm is affected by the presence of the other species. Consequently, species interaction was not observed. Although the specific cellular growth rate of K. pneumoniae is five times that of P. aeruginosa, the former species did not dominate the microbial population in the biofilm. Possible reasons for this unexpected behavior are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370813
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  • 9
    Electronic Resource
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    Modeling fermentations with recombinant microorganisms: Formulation of a structured model (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 802-808 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple structured model is described and compared with experimental data for fermentations with recombinant. Escherichia coli. The model is a so-called compartment, model, where the different biomass components are lumped together in a few intracellular variables. The model is able to describe, in a biologically reasonable fashion, a majority of the observations that have been made through fermentations with recombinant microorganisms. The model is especially suited for description of dynamic changes in plasmid copy number, e.g., runaway plasmid replication.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370903
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  • 10
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    Absorption of CO2 in algal mass culture systems: A different characterization approach (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 834-842 
    Details
    ISSN: 0006-3592
    Keywords: microalgae ; bioreactor ; CO2 ; absorption ; KLa ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For the characterization of CO2 absorption in aerated microalgal culture systems, a different approach based on KLa(O2) determination and transformation was studied. To confirm the validity of this method, the influence of reactions between CO2 and compounds (OH-, H2O, and NH3) present in the culture medium upon the absorption mechanism was evaluated under different physical and chemical culture conditions. Under these conditions, knowledge of the relative magnitudes of the diffusion and reaction kinetics permitted the evaluation of their relative importance. For the determination of the parameters required for the calculation of the CO2 absorption constant, empirical correlations for KL0 and a were used that had been previously verified with experimental data for O2 absorption. Since, for the conditions studied, the absorption rate was shown to be independent of the chemical reactions taking place in the liquid phase, the KLa for CO2 could be directly related to the KLa for O2 by a simple factor that took into account the difference in aqueous diffusivity of the two gases. Thus, using methods developed for determining O2 absorption in gas-liquid contactors, it is possible to adequately characterize CO2 absorption for laboratory and pilot scale algal production systems.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370907
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  • 11
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    Enzymatic syntheses of alkyds. II: Lipase-catalyzed polytransesterification of dichloroethyl fumarate with aliphatic and aromatic diols (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 883-888 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370913
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  • 12
    Electronic Resource
    Electronic Resource
    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    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.260371001
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  • 13
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    Photosynthetic activity of plant cells solubilized in water-in-oil microemulsions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 918-921 
    Details
    ISSN: 0006-3592
    Keywords: plant cells ; photosynthesis ; microemulsion ; organic solvents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: With the aim of possibly extending plant microbiology and photosynthesis beyond the usual applicability in aqueous solution, we investigated the solubilization of plant cells inorganic media with the help of water-in-oil microemulsions. Cells isolated from leaves of Rumex obtusifolius were solubilized in a water/2-ethyl-hexyl-sodiumsulfosuccinate/isooctane system, containing 20% water (v:v) and 240 mM surfactant, and the oxygen evolution/consumption was measured polarographically. Although no oxygen evolution was detectable in the organic medium, the cells were able to carry out photosynthetic oxygen consumption at the expense of ascorbate. To a lesser extent, photosynthetic oxygen consumption was measured using N, N, N′, N′-tetramethyl-p-phenylenediamine as electron donor. The rate of ascorbate photooxidation was linearly related to the concentration of cells.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260371004
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  • 14
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    A study of the energetics and economics of microalgal mass culture with the marine chlorophyte Tetraselmis suecica: Implications for use of power plant stack gasesHawaii Institute of Marine Biology Contribution No. 819. (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 936-947 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The marine phytoplankter Tetraselmis suecica was grown in shallow outdoor flumes for a period of approximately 6 months at the Natural Energy Laboratory of Hawaii. In full sunlight, gross production rates were 15-20 g C m-2 d-1. The corresponding photosynthetic efficiencies (PE's) were 9-10%. Respiration losses removed about half the gross production. The CO2 utilization efficiencies of 96 ± 11% were achieved by bubbling CO2 into the culture with the use of a counterflow sump system. Adding the CO2 in the form of carbonated water resulted in utilization efficiencies of 81 ± 11%. Archimedes screws proved superior to both paddle wheels and propellers as a means of circulating the water in the flumes. Insertion of foil arrays into the flumes to effect systematic mixing of the culture significantly enhanced production. The enhancement was greater when the foils were oriented at a small angle relative to the horizontal than when they were oriented at the same angle relative to the vertical. Light modulation effects are implicated as the probable cause of most of the enhancement. Substitution of electric power plant stack gases for pure CO2 resulted in no significant change in the production of T. suecica grown in chemostat culture.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260371007
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  • 15
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    Papain kinetics in the presence of a water-miscible organic solvent (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 967-972 
    Details
    ISSN: 0006-3592
    Keywords: papain ; organic solvent ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of various concentrations of a water-miscible organic solvent [a 7:3 (v/v) mixture of N, N dimethylformamide and dimethylsulfoxide] on the kinetics of papain have been investigated. The parameters kcat and Km for the amidase and esterase activity of papain using N-α-benzoyl-DL-arginine-p-nitroanilide (BAPNA) and N-α-benzoyl-L-arginine ethyl ester (BAEE) as substrates were determined. For both types of activity, kcat initially increased (up to about 15% solvent), and then decreased with increasing concentrations of organic solvent. In contrast, Km increased sharply with the organic solvent concentration. Active site titration at 0 and 50% solvent indicated no change in the amount of active enzyme. Fluorometric measurements of the emission spectrum of papain did not indicate any major conformational changes with increasing concentrations of organic solvent.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260371011
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  • 16
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    Analysis of polymer synthesis rates during steady-state growth of X. campestris (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 383-385 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370413
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  • 17
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    Effect of continued exposition to ethanol on activity of the ammonium and fructose transport systems in Saccharomyces cerevisiae var. ellipsoideus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 389-391 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ethanol and cycloheximide inhibited the function of the ammonium transport system in growing cultures of Saccharomyces cerevisiae var. ellipsoideus measured as methylamine uptake. The effect was reversible with ethanol and irreversible with the antibiotic. The kinetic data are consistent with a reduction of the number of active carrier molecules located in the plasma membrane. In contrast, neither ethanol nor cycloheximide affected the specific rate of fructose uptake.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370415
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  • 18
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    Plant cell bioreactor for the production of protoberberine alkaloids from immobilized Thalictrum rugosum cultures (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 397-403 
    Details
    ISSN: 0006-3592
    Keywords: immobilized Plant cells ; plant cells bioreactor ; Protoberberine Alkaloids ; Thalictrum rugosum ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cultured Thalictrum rugosum cells were immobilized using a glass fiber substratum previously shown to provide optimum immobilization efficiency based on spontaneous adhesion mechanisms. When cultivated in shake flasks, immobilized cells exhibited decreased growth and protoberberine alkaloid production rates in comparison to freely suspended cells. Since alkaloid production is growth associated in T. rugosum, the decreased specific production rate was a function of the slower growth rate. Cells immobilized on glass fiber mats appear to be amenable for extended culture periods. Maximum biomass and protoberberine alkaloid levels were maintained for at least 14 days in immobilized cultures. In contrast, fresh weight, dry weight, and total alkaloid content decreased in suspension cultures following the linear growth phase.Glass fiber mats were incorporated in to a 4.5-L plant cell bioreactor as horizontal disks supported on a central rod. Mixing in the reactor was provided by the combined actions of a magnetic impeller and a cylindrical sparging colum. fThe magnetic impeller and a cylindrical sparging column. The entire inoculum biomass of T. rougosum, introduced as suspension, was spontaneously immobilized with in 8h. During liner phase, the growth rate of bioreactor cultivated immobilized cells (μ = 0.06 day-1) was 50% that immobilized cell viability in both systems was determined to be similar. The increase in specific production of protoberberine alklodis was initially similar in bioreactor-and culture period. The increase in specific production of protoberberine alkaloids was initially similar in bioreactor-and shake-flask-cultivated immobilized cells. However, the maximum specific production of bioreactor grown cultures was lower. The scale up potential of an immobilization strategy based on the spontaneous adhesion of immobilization strategy based on the spontaneous adhesion of cultured plant cells to glass fiber is demonstrated.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370502
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  • 19
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    Quantitative evaluation of the pH profile in organic acid fermentations (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 190-195 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No Abstrct.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370212
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  • 20
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    Mass transfer characterization of an airlift probe for oxygenating and mixing cell suspensions in an NMR spectrometer (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 205-209 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxygen transfer characteristics of a 20-mm O.D. airlift contactor fitted with an oxygen microelectrode were determined by steady-state sulfite oxidation measurements. The volumetric mass transfer coefficient kLa was proportional to sparging power input per unit volume raised to a power which varied from 0.41 in water (coalescing bubbles) to 0.76 in NaCl solutions (noncoalescing bubbles). The highest observed kLa value was 0.012 s-1 which is sufficient to aerate Escherichia coli in an NMR spectrometer at moderate to high cell densities, depending on the physiological state of the cells.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370303
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  • 21
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    A parametric study ot protease production in batch and fed-batch cultures of Bacillus firmus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 467-483 
    Details
    ISSN: 0006-3592
    Keywords: alkaline protease ; Bacillus firmus ; extracellular enzymes ; nitrogen/oxygen/phosphorous limitation ; acetic acid ; ethanol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Proteolytic enzymes produced by Bacillus species find a wide variety of applications in brewing, detergent, food, and leather industries. Owing to significant differences normally observed in culture conditions promoting cell growth and those promoting production of metabolites such as enzymes, for increased efficacy of bioreactor operations it is essential to identify these sets of conditions (including medium formulation). This study is focused on formulation of a semidefined medium that substantially enhances synthesis and secretion of an alkaline protease in batch cultures of Bacillus firmus NRS 783, a known superior producer of this enzyme. The series of experiments conducted to identify culture conditions that lead to improved protease production also enables investigation of the regulatory effects of important culture parameters including pH, dissolved oxygen, and concentrations of nitrogen and phosphorous sources and yeast extract in the medium on cell growth, synthesis and secretion of protease, and production of two major nonbiomass products, viz., acetic acid and ethanol. Cell growth and formation of the three nonbiomass products are hampered significantly under nitrogen, phosphorous, or oxygen limitation, with the cells being unable to grow in an oxygen-free environment. Improvement in protease production is achieved with respect to each culture parameter, leading in the process to 80% enhancement in protease activity over that attained using media reported in the literature. Results of a few fed-batch experiments with constant feed rate, conducted to examine possible enhancement in protease production and to further investigate repression of protease synthesis by excess of the principal carbon and nitrogen sources, are also discussed. The detailed investigation of stimulatory and repressory effects of simple and complex nutrients on protease production and metabolism of Bacillus firmus conducted in this study will provide useful guidelines for design of bioreactors for production of protease and bulk chemicals by this bacterium.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260370509
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  • 22
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    Development of pure culture biofilms of P. putida on solid supports (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 512-518 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pseudomonas putida biofilms were developed on and biofilm accumulation rate data were obtained for the following two classes of support materials: charged surfaces and noncharged hydrophobic and hydrophilic surfaces. The effects of surface roughness and porosity on the rate of microbial attachment were also examined.Materials bearing a net positive or negative surface charge supported the greatest biofilm accumulation and the highest biofilm accumulation rate. Uncharged hydrophobic materials achieved the next greatest biofilm accumulation, averaging approximately 50% of the total biomass which was accumulated on the charged surface materials after 16 days. Uncharged hydrophilic materials supported very little biofilm development. In general, biofilm accumulation increased with decreased surface roughness. The effect of pore size on biofilm accumulation was not conclusive.The biofilm accumulation kinetics showed an exponential accumulation rate for the charged surfaces and an approximately linear accumulation rate for the hydrophobic materials. This difference in accumulation kinetics is consistent with proposed differences in the physicochemical mechanism governing attachment to these two types of surface materials.
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    Kinetics of loss of a recombinant plasmid in Bacillus subtilis (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 927-935 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus subtilis ; recombinant plasmid ; deletion rate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recombinant plasmid pCEDS is structurally unstable in Bacillus subtilis cultures. We have previously shown that stability can be independently increased by changing from a complex medium supporting high growth rates to a chemically-defined medium supporting a lower growth rate and removal of a 4.77-kb EcoRI fragment from pCED3 to give plasmid YS1. Further stabilization was achieved by combining the two approaches. In the present work, we show that the stabilization of the plasmid-encoded LacZ+ phenotype can be explained solely by the effect on the growth rate ratio between cells containing modified and parental plasmids. By using modified stability experiments (where a single cell rather than a suspended colony was used to initiate growth), independent growth rate measurements, and a simple mathematical model, we can describe the kinetics of the loss of the LacZ+ phenotype in terms of two variables, α and p (where α is the ratio of growth rates between modified and parental cells, and p is the probability of obtaining modified cells from parental cells). Under the conditions tested, the average values of α were 1.52 for cultures growing in complex medium, 1.28 for cultures growing in defined medium, and 1.18 for cultures containing the modified plasmid pYS1 growing in complex medium. The calculated p values ranged between 10-8 and 10-10 under all conditions. Plasmid (pYS137) was used to directly estimate plasmid deletion rates in B. subtilis and it showed a rate between 5 × 10-8 and 1.1 × 10-9 deletions/cell/generation. In contrast to B. subtilis, there were no detectable differences in growth rates between Escherichia coli strains harboring plasmid pCEDS and plasmid-free cells. These results explain the observed stability of pCEDS in E. coli cultures and indicate that readily detected instability in B. subtilis cultures can be the result of rare deletion events.
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    Oxygen transfer in slurry bioreactors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 960-966 
    Details
    ISSN: 0006-3592
    Keywords: bioreactors ; oxygen transfer ; fermentation ; mycelial fermentation ; mass transfer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxygen transfer in bioreactors with slurries having a yield stress was investigated. The volumetric mass transfer coefficients in a 40-L bubble column with simulated fermentation broths, the Theological properties of which were represented by the Casson model, were measured. Experimental data were compared with a theoretical correlation developed on the basis of a combination of Higbie's penetration theory and Kolmogoroff's theory of isotropic turbulence. Comparisons between the proposed correlation and data for the simulated broths show good agreement. The mass transfer data for actual mycelial fermentation broths reported previously by the authors were re-examined. Their Theological data was correlated by the Bingham plastic model. The oxygen transfer rate data in the mycelial fermentation broths fit the predictions of the proposed theoretical correlation.
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    Effect of medium osmolarity on hybridoma growth, metabolism, and antibody production (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 989-993 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
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    Ultrasound-enhanced bioprocess. II: Dehydrogenation of hydrocortisone by Arthrobacter simplex (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 998-1003 
    Details
    ISSN: 0006-3592
    Keywords: Arthrobacter simplex ; controlled ultrasonic irradiation ; microbial conversion ; ultrasound facilitated diffusion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dehydrogenation of hydrocortisone by agitated suspensions of free and immobilized cells of Arthrobacter simplex ATCC 6946 was investigated under controlled ultrasonic irradiation at a frequency of 20 kHz. The microbial conversion was optimized first with respect to mechanical agitation and subsequently with respect to an additionally superimposed sonication. The optimization of ultrasound intensity and its mode of application were established at a level which maintained the structural integrity of the cells as well as their biocatalytic activity. Various regimes of ultrasound at power densities of 0.030-0.120 W/mL were applied in systems of soluble (0.4 g/L) and excess (1 g/L) hydrocortisone and only a moderate enhancement of the bioconversion by free cells was observed. This result was explained by a better ultrasound-induced dispersal of microscopic clumps of cells and self-adhering clusters of the steroids. However, a quite significant enhancement effect was obtained in bioconversion systems of soluble substrate by gel-entrapped cells. This enhancement was explained by a phonophoretic effect associated with ultrasound-facilitated diffusion of the substrates - oxygen and hydrocortisone - within the gel beads.
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    The biodegradation of mixtures of organic solvents by mixed and monocultures of bacteria (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1037-1042 
    Details
    ISSN: 0006-3592
    Keywords: biodegradation ; organic solvents ; biooxidation ; bacteria ; competition interactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Much more information concerning the biodegradation kinetics of mixtures of common industrial chemicals, such as organic solvents, needs to be gathered before wastewater biotreatment process performance can become a matter of design. Here, the biooxidation of a solvent mixture comprizing methanol, acetone, isopropanol, and methylene chloride is examined. The fact that the enrichment culture obtained comprized only two solvent-utilizing strains, together with only minor percentages of nonsolvent utilizing satellite strains, was contrary to the theory of microbial competition. In addition, the complex relationship between the two solvent-utilizing strains indicates that further work is necessary on the pathways involved in isopropanol and acetone biooxidation and on the effects of operating conditions on the fluxes along such pathways.
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    A molecular model for singlet/singlet energy transfer of monovalent ligand/receptor interactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1066-1075 
    Details
    ISSN: 0006-3592
    Keywords: Resonance energy transfer ; papain ; concanavalin A ; molecular model ; monovalent ligand and receptor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A stochastic model is described that predicts the degree of singlet/singlet energy transfer in complexes formed between monovalent ligands and monovalent receptors. The modeling approach is intended to serve as an analytical tool for approximating the level of fluorescence quenching that can be expected to occur in fluorescently labeled monovalent ligands and receptors that are bound together in complexes. This approach has utility in areas such as modeling protein/protein interactions and designing fluorescence energy transfer assays.Using the crystallographic data for papain (monovalent ligand ) and concanavalin A (monovalent receptor ) along with a molecular graphics computational package the ligand and receptor were docked together to form a ligand/receptor complex. The intermolecular distances between the lysine resides of the ligand and receptor were then estimated, receptor complex was calculated assuming a value for the characteristic length R0 of the donor/acceptor pair. Results from the stochastic model were used to calculate the level of fluorescence quenching one would expect for a resonance energy transfer competition assay based on the monovalent ligand/pair.Three key assumptions were made during the model development. First, all lysine resides for the ligand and receptor were equally reactive with the dye molecules so the stoichiometry of the donor and acceptor chromophores was governed by a binomial distribution. Second, the dye molecules were located at the α-carbon position for each reactive lysine residue. Finally, in the energy transfer competition assay, it was assumed that equilibrium existed between the ligand, receptor, and competing hapten at all times. Based on these assumptions, results are presented that indicate the maximum energy transfer for the monovalent papain/concanavalin. A complex is strongly dependent on the number of acceptor chromophores and on the value of R0. Results are also presented on the approximate level of fluorescence quenching that may occur in a competition assay based on the papin/pConA complex. Lastly, a strategy is discussed for maximizing the dynamic range and linearity of energy transfer assays by optimizing several key design variables.
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    Optimization of L-malic acid production by Aspergillus flavus in a stirred fermentor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1108-1116 
    Details
    ISSN: 0006-3592
    Keywords: organic acids ; Aspergillus flavus ; molar yield ; stirred fermentor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effects of various nutritional and environmental factors on the accumulation of organic acids (mainly L-malic acid) by the filamentous fungus Aspergillus flavus were studied in a 16-L stirred fermentor. Improvement of the molar yield (moles acid produced per moles glucose consumed) of L-malic acid was obtained mainly by increasing the agitation rate (to 350 rpm) and the Fez+ ion concentration (to 12 mg/L) and by lowering the nitrogen (to 271 mg/L) and phosphate concentrations (to 1.5 mM) in the medium. These changes resulted in molar yields for L-malic acid and total C4 acids (L-malic, succinic, and fumaric acids) of 128 and 155%, respectively. The high molar yields obtained (above 100%) are additional evidence for the operation of part of the reductive branch of the tricarboxylic acid cycle in L-malic acid accumulation by A. flavus. The fermentation conditions developed using the above mentioned factors and 9% CaCO3 in the medium resulted in a high concentration (113 g/L L-malic acid from 120 g/L glucose utilized) and a high overall productivity (0.59 g/L h) of L-malic acid. These changes in acid accumulation coincide with increases in the activities of NAD+-malate dehydrogenase, fumarase, and citrate synthase.
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    Lipase-catalyzed hydrolysis of 2-naphtyl esters in biphasic system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 30-36 
    Details
    ISSN: 0006-3592
    Keywords: lipase-catalyzed hydrolysis ; 2-naphtyl ester ; biphasic system ; interfacial reaction ; two-film model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The authors measured the rate of hydrolysis of the homologs of 2-naphtyl ester by using a Lewis cell with constant interfacial area to elucidate the kinetic mechanism of the lipase-catalyzed hydrolysis in biphasic system. On the basis of the two-film model, it was found from the analysis of experimental results that the hydrolysis of these substrates proceeds at the interface between the aqueous and organic phases. The interfacial reaction rate could be correlated by Michaelis-Menten mechanism. The values of the rate constant and the Michaelis constant were almost independent of the kinds of 2-naphtyl ester. The values of the interfacial kinetic parameters for 2-naphtyl ester were much greater than those for the hydrolysis in the aqueous phase.
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    Modeling growth and succinoglucan production by Agrobacterium radiobacter NCIB 9042 in batch cultures (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 65-74 
    Details
    ISSN: 0006-3592
    Keywords: Succinoglucan ; Agrobacterium radiobacter ; Structured model ; ATP ; cofactors balances ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Wild-type Agrobacterium radiobacter NCIB 9042 has been cultivated in batch cultures on a synthetic medium which was adapted for growth and succinoglucan production. Experiments were carried out in a 4-L stirred-tank aerated reactor. Glucose, biomass, polysaccharide, protein, and inorganic- and organic-nitrogen concentrations were measured, and oxygen consumption and CO2 production rates were obtained by a gas-balance technique. Nitrogen balance shows that inorganic nitrogen is entirely recovered into proteins. The carbon balance is satisfied with in ±5%. Stoichiometric equations for biomass growth and succinoglucan synthesis were established. The biosyntheticpolymer pathways including ATP and cofactor consumption were investigated. From previous studies, a (P/O) value of 1.66 is selected for oxygen sufficient cultures. The actual ATP requirements of 25.4 mmol ATP/g succinoglucan (38.5 mol ATP/mol succinoglucan), determined by a metabolic analysis, is 2.39 times the stoichiometric value. Experimental results were modeled by a system of differential equations. The exponential growth phase was described by a nitrogen-limited Monod equation. Subsequent succinoglucan synthesis followed a slightly modified Luedeking-Piret relation partitioning internal and external polysaccharide. Experimentally determined coefficients are compared with published results for continuous culture of A. radiobacter NCIB 11883.
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    Development of biosensors for the simultaneous determination of sucrose and glucose, lactose and glucose, and starch and glucose (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 99-103 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sensors for the simultaneous determinations of sucrose and glucose, lactose and glucose, and starch and glucose were prepared by a combination of the enzyme system shown below and an oxygen electrode: The mechanism for separating the substrates with the proposed sensors is based on the time lag arising from reaction and diffusion. Invertase, β-galactosidase, amyloglucosidase, mutarotase, and glucose oxidase were covalently immobilized on triacetyl cellulose membranes containing 1,8-diamino-4-aminomethyloctane. A glucose oxidase membrane, mutarotase membrane, three sheets of triacetyl cellulose membranes, and invertase, or β-galactosidase or amyloglucosidase membrane were placed in that order on the tip of the oxygen electrode. Calibration curves for sucrose, lactose, and starch were linear up to 40 mM, 60-180 mM, and 10%, respectively. The simultaneous determination of sucrose and glucose, lactose and glucose, and starch and glucose was possible when the amount of glucose coexised was in the range of 2-16% sucrose, 2.8-8.3% lactose, or 0.1-1% starch. The relative errors were ±4% for sucrose and ±3% for lactose in 100 assays. The starch sensor was reused only five times. Each enzyme membrane was fairly stable for more than 10 days.
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    α-Amylase adsorption on starch crystallites (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 127-134 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus subtillis ; binding free energy ; Adsorption isotherm ; monolayer adsorption process ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The goal of this work was to characterize the adsorption of Bacillus subtills α-amylase onto crystalline starchy materials of the B-type polymorph. Monodisperse spherulitic particles (R ż6; 5.0 μm), essentially resistant to α-amylolysis at 25°C were prepared from short amylose chains (DPn ≈ 15). The α-amylase adsorbed specifically onto the spherulites, and adsorption was found to be a prerequisite step for hydrolysis. Adsorption was inhibited by the presence of maltose and maltotriose in the reaction mixture. Adsorption isotherm of the enzyme on the particles showed a well developed plateau of 1.62 μg/cm2 at 25°C corresponding to a monolayer adsorption process. The binding free energy calculated from the initial slope of the isotherm was ΔG ≈ -20.7 kJ/mol. This is smaller than published values for the binding of α-amylase to soluble amylosic chains (ΔG 〈 -30 kJ/mol).
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    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.260371101
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    Enzymatic synthesis of esters using an immobilized lipase (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1004-1009 
    Details
    ISSN: 0006-3592
    Keywords: esterification ; immobilized enzymes ; enzymes in organic solvents ; enzyme activity and stability ; continuous enzymatic synthesis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various esters were synthesized in nearly anhydrous hexane from alcohols and carboxylic acids using a lipase from Candida cylindracea. The enzyme was immobilized on a nylon support and protein loadings as high as 10 mg/g were obtained. The activity of the immobilized enzyme was maximum in a range of temperatures from 25 to 37°C. Ethylpropionate was formed from ethanol and propionic acid at a rate of 0.017 mol/h g immobilized protein. Different esters were formed at comparable rates and equilibrium conversions could generally be approached in less than 10 h in a batch reaction system. The immobilized lipase catalyst was quite stable and retained about one third of the initial activity after repeated experiments during the course of 72 days. A stirred tank continuous flow reactor was used successfully for the continuous production of esters.
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    Increased protein productivity from immobilized recombinant yeast (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1029-1036 
    Details
    ISSN: 0006-3592
    Keywords: immobilization ; protein production ; continuous culture Saccharomyces cerevisiae ; plasmid stability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Saccharomyces cerevisiae strain Mc16/p520 has an unstable plasmid, p520, which directs production of a wheat α-amylase. The effects of immobilizing this microorganism on the plasmid stability and the specific productivity of the secreted α-amylase were investigated. Small gelatin beads were used as the support in both fluidized and packed bed configurations, and the yeast cells were attached by covalent cross-linking with glutaraldehyde. These data were then compared to those for nonimmobilized, suspension cells.Plasmid stability was increased for the immobilized cells during continuous culture at dilution rates both above and below washout. Continuous suspension cultures were not stable and rapidly lost the plasmid. Immobilization caused an increase in specific and volumetric productivity during continuous culture, with a packed bed design resulting in the highest specific productivity.
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    Oxygen uptake by entrapped hybridoma cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1050-1053 
    Details
    ISSN: 0006-3592
    Keywords: hybridomas ; immobilization ; oxygen ; respiration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Oxygen consumption by hybridoma cells immobilized in 1- and 3.9-mm-diameter calcium alginate beads was measured. The entrapped cells consumed oxygen at about 10 μmol/min per 109 cells, regardless of the bead size and cell loading. In contrast, the same cells in suspension culture respire at specific rates of 3-8 μmol/min per 109 cells (depending on the cell density). The growth rate of the immobilized cells was significantly reduced, while specific antibody production was comparable to that of free cells.
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    A novel technique for the measurement of disruption in high-pressure homogenization: Studies on E. coli containing recombinant inclusion bodies (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 363-370 
    Details
    ISSN: 0006-3592
    Keywords: homogenization, high-pressure ; cell disruption ; inclusion bodies ; size distribution ; centrifuge, analytical ; Escherichia coli ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The high-pressure homogenization of Escherichia coli, strain JM101, containing inclusion bodies of recombinant porcine somatotropin was investigated. A novel technique employing an analytical disc centrifuge was used to monitor the disruption. This a direct technique which measures cell disintegration rather than soluble protein release. The technique is particularly suited to measurements where the disruption approaches 100%. The disk centrifuge provides a size distribution of the homogenate, and furnishes evidence for the preferential disruption of larger cells. For E. coli containing inclusion bodies, and increase in the cell feed concentration from 145 g/L (wet weight) to 330 g/L resulted is poorer homogenization. Poorer disruption was also obtained by lowering the feed temperature from 20°C to 5°C. Only slight variations in performance were obtained by increasing the feed pH from 7.5 to 9.0 or by storing the feed at 4°C for 24 h prior to disruption. Comparison with uninduced E. coli strain JM101, showed that the disruption obtained is higher for bacteria containing a recombinant inclusion body.
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    Characteristics of batch culture of a recombinant bacillus brevis excreting a foreign esterase (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1247-1252 
    Details
    ISSN: 0006-3592
    Keywords: batch culture ; Bacillus brevis ; esterase ; host-vector system ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The productivity of extracellular enzyme was evaluated in batch culture using a protein hyperexcreting host, Bacillus brevis HPD315 harboring pHSC131, which carried a gene (est) encoding esterase activity from Bacillus stearother mophilus. Optimum temperature and pH for the bacterial growth and the production of extracellular esterase were found to be 35°C and pH 6.5, by using the standard medium (GPY) containing neomycin as a selective pressure, Under the cultivation condition employed, cell growth reached 5 g dry cell weight/L, while the extracellular esterase activity amounted to 4.5 U/mL. Most (79%-92%) of the esterase produced was excreted into the medium. pHSC131 was stably retained in the host cell during cultivation in the presence of neomycin. However, in the absence of neomycin, the plasmid was completely lost from the host after 12-h cultivation accompanied by decreases in both esterase activity and production of total extracellular protein. The copy number of the plasmid was estimated to be approximately 7 throughout the cultivation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the excreted proteins showed the presence of a protein having an apparent molecular weight of 32,000, which equals to the value predicted from the DNA sequence of the est gene.
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    Cellulase production by Trichoderma reesei when cultured on xylose-based media supplemented with sorbose (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 12-16 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The ability of L-sorbose to stimulate cellulase production In shake flask culture of Trichoderma reesei was examined in mineral salts media (initial pH 5.0) containing either 1.0% D-xylose, 1.0% cellulose, and/or 0.1, 0.3, or 0.5% L-sorbose. When sorbose was the only carbon source, growth was limited, little substrate was utilized, pH increased, and cellulase activity was not apparent. The other carbon sources promoted good growth, pH dropped sharply to 2.5-3.0, substrate was utilized rapidly, and cellulase activity was detected. After three weeks of fermentation, twice as much cellulase activity was detected in the medium containing only cellulose as the carbon source, as compared to xylose as the carbon source. Cellulase activity was higher when media contained xylose supplemented with sorbose compared to xylose as the only carbon source. At 0.3 and 0.5% levels of sorbose supplementation of xylose-based media, cellulase activity was similar to that in cellulose-based media.
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    Physiological changes during the adaptation of hybridoma cells to low serum and serum-free media (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 35-46 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two murine hybridoma cell lines (167.4G5.3 and S3H5/γ2bA2) were adapted to grow in low-serum and serum-free media by a weaning procedure. The changes in cell growth, metabolic, and antibody production rates with adaptation were examined using biochemical and flow cytometric analyses. After adaptation to a particular serum level, the short-term serum response of the cells was experimentally determined. Specific growth rates, glucose and glutamine uptake and lactate and ammonia production rates, and specific antibody production rates were evaluated from the data. For both cell lines, an improvement in cell growth was observed after adaptation, and both higher growth rates and higher cell concentrations were obtained. The specific glucose and glutamine uptake rates and the lactate and ammonia production rates changed insignificantly with adaptation. Conversely, changes in the specific antibody production rate of the two cell lines differed. Cell line 167.4G5.3 showed a loss in antibody productivity at low serum levels, while the S3H5/γ2bA2 kept its original productivity in low-serum-containing media. The intracellular antibody content for S3H5/γ2bA2 cells remained unaltered by adaptation, but a low antibody containing cell population appeared in the 167.4G5.3 culture. The loss of specific antibody productivity in this cell line was due to the appearance of this population.
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    Model of oxygen transport limitations in hollow fiber bioreactors (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 80-92 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Axial and radial oxygen depletion are believed to be critical scale-limiting factors in the design of cell culture hollow fiber bioreactors. A mathematical analysis of oxygen depletion has been performed in order to develop effectiveness factor plots to aid in the scaling of hollow fiber bioreactors with cells immobilized in the shell-side. Considerations of the lumen mass transport resistances and the axial gradients were added to previous analyses of this immobilization geometry. An order of magnitude analysis was used to evaluate the impact of the shell-side convective fluxes on the oxygen transport. A modified Thiele modulus and a lumen and membrane resistance factor have been derived from the model. Use of these terms in the effectiveness factor plots results in a considerable simplification of the presentation and use of the model. Design criteria such as fiber dimensions and spacing, reactor lengths, and recycle flow rates can be selected using these plots. Model predictions of the oxygen limitations were compared to experimental measurements of the axial cell distributions in a severely oxygen limited hollow fiber bioreactor. Despite considerable uncertainty in our parameters and nonidealities in hollow fiber geometry, the cell distribution correlated well with the modeling results.
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    Reaction kinetics in biofilms (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 877-882 
    Details
    ISSN: 0006-3592
    Keywords: microtechnique ; microprobe ; biofilm ; dissolved oxygen concentration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel in situ microtechnique allows evaluating parameters of diffusion-controlled reactions in biofilms. A microprobe, 15 μm in diameter, was used to simultaneously measure the dissolved oxygen concentration and the optical density at different depths in a submerged biofilm. Based on the results, the biofilm diffusion coefficient for dissolved oxygen, Df the dissolved oxygen flux through the biofilm surface, J02, and the half velocity coefficient, Ks, have been calculated.
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    Fluorescence modeling in a multicomponent system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 907-922 
    Details
    ISSN: 0006-3592
    Keywords: fluorescene monitoring ; inner-filter effect ; biosensor ; tryptophan ; tyrosine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An extensive fluorescence database for binary tyrosinetryptophan mixtures utilizing 280 nm excitation was collected. The database spanned three orders of magnitude (10-6M-10-3M) and covered all compositions within this range. A generalized model for describing the multicomponent fluorescence signals as a function of emission wavelength, excitation wavelength, and sample composition was derived. A geometric integral that contained all the geometric factors affecting fluorescence was introduced; thus the model was applicable to various configurations, including the three used in this study: an NADH probe, a backscatter laser-induced fluorescence setup, and a commercial spectroflurometer. A correction factor was proposed that allowed linearization of the fluorescence signals with respect to fluorophore concentrations. The effect of the water Raman on fluorescence spectra was also modeled. The model contains only two wavelength-dependent parameters for each of the components present in a sample, one specifying absorption of the excitation energy and the other specifying the species' fluorescence tendency. These wavelength-dependent parameters were correlated with polynomials. The average prediction error at each wavelength was 10-20%, a major portion of which was attributed to experimental uncertainties.
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    Protein immobilization to polystyrene via long poly(ethylene lycol) chains (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 952-955 
    Details
    ISSN: 0006-3592
    Keywords: human albumin ; Protein conjugate ; caionic polymer ; PEG chains ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Human albumin has been attached to 24-hole polystyrene plates via branched poly(ethylene lycol) (PEG) spacer arms. A tetraepoxude of PEG of molecular weight (1.4-1.5) × 104 g/mol was reacted with the protein in solution allowing approximately one-third of the oxirane rings to react. The protein conjugate was then coupled to the long, cationic polymer poly(ethylene imine) (PEI), and the protein-PEG-PEI adduct was subsequently adsorption to unmodified polystyrene. Since the protein is linked to the surface via long, hydrophilic and nonchargedchains, interactions between the biomolecule and the surface is minimized.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991) 
    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.260380901
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    Differential product release (DPR) of proteins from yeast: A new technique for selective product recovery from microbial cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 977-985 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel method has been developed for the separation of bioproducts from yeast cells. The method uses a combination of physical, chemical, and biological agents such as lytic enzymes, osmotic supports, and spheroplast stabilizers. Using this technique, products (proteins and enzymes) can be released from specific cell locations at different process states; it has thus been celled differential product release (DPR). The wall-associated proteins are released first and the lytic enzyme is removed together with the wall proteins at this stage. Secondly, the cytosol products are released by a mild procedure during which the organelles remained intact. Finally, the organelle proteins are solubilized. In each stage, specific proteins are released while others are kept inside the different cell compartments. This method can be used with relatively high yeast concentrations (up to 145 g dry wt/L) and gives higher product recoveries and much higher selectivity than mechanical disruption.
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    Long-term perfusion culture of hybridoma: A “grow or die” cell cycle system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 781-787 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma culture ; monoclonal antibody production ; perfusion culture ; continuous culture ; cell cycle ; tangential filtration ; cell separation ; nuclepore membranes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to elucidate the hybridoma life cycle and the limiting factors in perfusion systems, we performed cultures in a stirred tank bioreactor, coupled to an external tangential flow filtration unit. Cell density and antibody production in perfusion were consistent with previous studies. The average life span of the cells (2.1-2.2 days), antibody, productivity per cell produced (30-38 mg/109 cells) and cell size diameter evolution appeared similar to values observed in batch cultures. These observations highly suggest a similar “grow or die” life cycle. Cell and antibody production, strictly related to the medium perfusion rate, seem to be under the control of the nutrient availability. A hypothesis to explain such a life cycle of hybridoma cells in perfusion systems and a model for viable and dead cell density is proposed.
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    Kinetic parameters of a mixed culture oxidizing sulfide and sulfur with oxygen (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 813-820 
    Details
    ISSN: 0006-3592
    Keywords: loading rate ; growth yield ; oxidation rate ; free-cell suspensions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetic parameters of biological sulfide oxidation are described. The influence of the sulfide loading rate on growth yield and specific oxidation rate were investigated with free-cell suspensions. It is concluded that at least two types of bacteria were present, namely, sulfate producers (type A) that grow at higher loading rates. Type A bacteria have a growth yield of 04 g dry S/mol S, while type B bacteria have a growth yield of 04 g dry S/mol S. Type A has a high affinity for sulfide and is inhibited by sulfide at sulfide concentrations exceeding 10 mg/L. Type B has a low affinity for sulfide and is not inhibited by sulfide, but by oxygen.
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    Use of a lipase immobilized in a membrane reactor to hydrolyze the glycerides of butteroil (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 853-868 
    Details
    ISSN: 0006-3592
    Keywords: A spergillus niger ; continuous hydrolysis ; membrane reactor ; butteroil ; immobilized lipase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A lipase from A spergillus niger, immobilized by adsorption on a microporous, polypropylene flat-sheet membrane, was used to effect the continous hydrolysis of the glycerides of melted butterfat at 35°C. For the reaction conditions used in this research, a pseudo-zero order rate expression can be used to model the kinetics of the overall hydrolysis of butterfat. Multiresponse nonlinear regression methods were employed to determine the kinetic parameters of a multisubstrate rate expression derived fro ma mechanism based on the general Michaëlis-Menten approach. For the multiresponse data taken at pH 7.0, the dependence of the maximum rate of release of each fatty acid residue of butterfat on its carbon chain length is accurately described by a skewed, bell-shaped (or Γ-type) distribution. Data taken at five different pH values were fit assuming a Dixon-Webb diprotic model for the pH dependence of the reaction rate. The thermal deactivation of the immobilized lipase obeyed first-order kinetics with a half-life of 19.9 days at 35°C. The multisubstrate model is useful for the prediction of the free fatty acid profile of lipolyzed butterfat, whereas the lumped-substrate model provides an estimate of the overall degree of hydrolysis as a function of the reactor space time.
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    Xylanase production by Aspergillus awamori. Development of a medium and optimization of the fermentation parameters for the production of extracellular xylanase and β-xylosidase while maintaining low protease production (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 883-890 
    Details
    ISSN: 0006-3592
    Keywords: Aspergillus awamori ; low protease production ; dinitrosalicylic method ; xylanase ; β-xylosidase ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A growth medium was developed for maximal production in batch culture of extracellular xylanase and β-xylosidase by Aspergillus awamori CMI 142717 and a mutant (AANTG 43) derived from the wild-type strain. The optimum pH for the production of xylanase and β-xylosidase was 4.0. The best temperature of xylanase production was 30°C; 35°C was optimal for β-xylosidase. Protease production was never completely suppressed under any of the conditions tested. However, protease titre was 3.5-fold less than the control in medium in which proteose peptone and yeast extract were omitted: the level of xylanase was not affected (8.6 U mL-1) but β-xylosidase titre was increased 4.7-fold to 1.5 U mL-1. When corn steep liquor was used as the sole nitrogen source, xylanse and β-xylosidase titres were further increased by 1.5- and 1.9-fold, respectively. Of the carbon sources investigated, ball-milled oat straw or oat spelt xylan produced the highest titres of xylanse and β-xylosidase. None of the soluble carbon sources investigated produced the high titres of xylanase or β-xylosidase induced by either oat straw for xylanse and β-xylosidase was 2% and the optimum spore inoculum was between 106 and 107 spores/mL-1 final concentration. The level of xylanse activity obtained in the culture filtrates of the mutant was a remarkable 820 U mL-1 when the reducing sugar released was measured by the dinitrosalicylic acid method. This enzyme titre would appear to be the highest reported so far. The xylanases system contained the correct balance of enzymes to effect extensive hydrolysis of oat spelt xylan. The protease titre was very low.
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    Kinetic analysis of cephalosporin biosynthesis in Streptomyces clavuligerus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 941-947 
    Details
    ISSN: 0006-3592
    Keywords: Streptomyces clavuligerus ; cephalosporin ; rate-limiting enzyme ; kinetic model ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model describing the cephalosporin biosynthesis in Streptomyces clavuligerus was developed. Using previously reported kinetic data of biosynthetic enzymes, we examined the kinetics of cephalosporin production. The predicted time profile of the specific production rate during a batch culture parallels that of experimental observation. Sensitivity analysis reveals that δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine (ACV) synthetase is the rate-limiting enzyme. The effect of amplifying ACV synthetase on the specific production rate was analyzed theoretically. Increasing ACV synthetase enhances the production rate initially until ACV synthetase enhances the production rate initially until deacetocycephalosporin C hydroxylase becomes rate-limiting. Such kinetic analysis can provide a rational basis for modifying the biosynthetic machinery of cephalosporin through gene cloning.
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    Effect of agitational shear on growth and protease production by Thermomonospora fusca (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 371-374 
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    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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    Minimizing the errors associated with the determination of effective diffusion coefficients when using spherical cell immobilization matrices (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 386-388 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gel materials are often used to entrap biological catalysts. Several experimental methods have been proposed to estimate the diffusion coefficient of important chemical species within these materials. An error analysis for the bead method was performed and, contrary to previously reported results, when proper experimental conditions were employed, the error associated with the bead method was similar to that obtained using the other common methods.
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    Determination of kinetic parameters related to the piasmid instability: For the recombinant fermentation under repressed condition (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 404-414 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The plasmid stability under the repressed state of cloned gene was studied theoretically as well as experimentally using recombinant E. coli K12ΔH1Δtrp/pPLc23trpA1 as a “host-vector” model system. The important kinetic parameters studied were the plasmid loss rate (θ) describing the rate at which the plasrnid-harboring cells lose plas-mids and the plasmid-free cells are generated per unit time and the difference in growth rates (Δ) between the two genotypes. These parameters were carefully defined, studied, and compared with other key kinetic parameters involved in the recombinant fermentation to further our understanding of metabolism of recombinants. The ratio of the concentration of plasmid-free cells to plasmid-harboring cells (Ω) was introduced, and the mathematical model was derived and used for the determination of the kinetic parameters associated with plasmid instability. These methods developed based on the theoretical considerations were tested experimentally. The results of these methods were compared, and the best method was selected and recommended. The effect of temperature and dilution rate on kinetic parameters θ and Δ were also studied in continuous culture, in order to provide some practical information related to the operation and control of recombinant fermentation processes.
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    Uptake of cadmium and zinc by the alga Chlorella vulgaris: II. Multi-ion situation (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 445-455 
    Details
    ISSN: 0006-3592
    Keywords: synergism antagonism ; metal uptake ; Chlorella vulgaris ; cadmium ; zinc ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many microorganisms are capable of sequestering and concentrating heavy metals from their aqueous environment. While much research has beep carried out on the uptake of single species of metal ions, little attention seems to have been given to the study of multimetal ion systems. A mathematical model has previously been developed to describe the uptake of individual metal species by a microorganism. The model proposes two sequential processes: an initial rapid uptake due to cellular surface adsorption and a subsequent slow uptake due to membrane transport of the metal into the cells. This article extends the treatment by considering the uptake of two metal species together, cadmium and zinc, under different experimental conditions. The results are discussed in terms of possible mechanistic interactions.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    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.260370601
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    Large-Scale, High-density freezing of hybridomas and its application to high-density culture (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1110-1113 
    Details
    ISSN: 0006-3592
    Keywords: high-density freezing ; high-density culture ; hybridoma ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large-scale, high-density freezing of hybridomas was studied to apply frozen cells to start high-density culture. We showed here that hybridomas can be frozen at 1.5 × 108 cells/mL, without decrement in viability and proliferating activity. Blood transporting bags were used for large-scale freezing to store 25 mL of cell suspension with a cell density, 1.5 × 108/mL. The number of cells stored in a bag (3.0 × 109 cells) was enough to start a high-density culture at a 10 times higher cell density (6.0 × 106 cells/mL) than normal inoculation, and the cells proliferated to 107 cells/mL within 2 days. These results indicate that the large-scale freezing method is useful for large-scale culture of mammalian cells.
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    Catalytic action of L-2-halo acid dehalogenase on long-chain L-2-haloalkanoic acids in organic solvents (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1114-1117 
    Details
    ISSN: 0006-3592
    Keywords: L-2-halo acid dehalogenase ; dehalogenation ; in dimethyl sulfoxide ; 2-hydroxy acids ; stereospecific production of substrate specificity ; change in organic solvent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Lyophilized preparation of L-2-halo acid dehalogenase was not only stable but also catalytically active in anhydrous dimethyl sulfoxide, toluene, and other organic solvents. 2-Halo acids with long alkyl (C5-C16) or aromatic (phenyl and benzyl) side chains were inert in water but dehalogenated effectively in anhydrous dimethyl sulfoxide by the lyophilized enzyme. Long chain 2-haloalkanoic acids such as 2-bromohexadecanoic acids were better as substrate than short-chain halo acids (e.g., 2-chloropropanoic acid). The dehalogenation proceed with inversion of C2 configuration to produce the corresponding (2R)-2-hydroxy acids in anhydrous dimethyl sulfoxide in the same way as found in water.
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    Immobilization-stabilization of α-chymotrypsin by covalent attachment to aldehyde-agarose gels (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1144-1152 
    Details
    ISSN: 0006-3592
    Keywords: stabilization of chymotrypsin ; enzyme-support multipoint attachment ; effect of denaturing agents ; 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 α-chymotrypsin by multipoint covalent attachment of the enzyme, through its amino groups, to agarosealdehyde gels. We have studied the role of the main variables that control the intensity of these enzyme-support multi-interaction processes (surface density of aldehyde groups in the activated gel, contact time between the immobilized enzyme and the activated support prior to borohydride reduction of the derivatives, etc.). In this way, we have prepared a number of very different chymotrypsinagarose derivatives. Our best derivatives, with the most intense multipoint attachment, were more stable than one-point attached derivatives and were more than 60,000-fold more stable than soluble enzyme in the absence of autolysis phenomena. In spite of the dramatic stabilization, the catalytic activity of these derivatives is little changed (they only lose 35% of intrinsic activity after this intense enzyme-support multi-interaction process). In addition, we have also demonstrated the very high capacity of 6% aldehyde-agarose gels to immobilize pure chymotrypsin (40 mg enzyme/mL catalyst). Furthermore, we have been able to establish a clear correlation between enzyme-support multipoint covalent attachment, stabilization against very different denaturing agents (heat, urea, organic cosolvents), and insensitivity of those immobilized chymotrypsin molecules to some activating agents.
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    Continuous production of Ammonium lactate by Streptococccus cremoris in a three-stage reactor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1173-1181 
    Details
    ISSN: 0006-3592
    Keywords: Streptococcus cremoris ; continuous three stage fermentation ; ammonium lactate ; whey permeate ; FACWP ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch and continuous fermentation studies were performed to optimize the production of ammonium lactate from whey to optimize the production of ammonium lactate from whey permeate. The product known as fermented ammoniated condensed whey permeate (FACWP) is a very promising animal feed. After an initial screening of four strains which produce predominantly L(+)- lactic acid, the desired isomer [D(-)-lactic acid is toxic], Streptococcus cremoris 2487 was chosen for further study. In batch mode, pH between 6.0 and 6.5 and 35°C provided optimum incubation conditions. To stimulate a plug flow reactor, three CSTRs (continuous stirred tank reactors) were connected in tandem. For a 7.5-h retention time, 1.6-fold and 1.3-fold higher productivities were obtained for three-stage than for the single- and two-stage reactors, respectively. Various retentions times were examined (5, 7.5, and 10 h; 5g/L yeast extract). Although maximum lactate productivity occurred at a 5-h residence time (5.38 g/L H. 75% lactose utilization), lactose utilization was more complete at 7.5 h (4.38 g/L h productivity, 91% lactose utilization and a productivity, 91% lactose utilization). Retention time was increased to 15 h to obtain 95.9% lactose utilization and a productivity of 2.42g/L h for 2g/L yeast extract. Based on this lower yeast extract concentration, it was determined that ammonium lactate production and subsequent concentration by 11-fold would yield a product (FACWP) 17% more than soybean meal (crude protein contents are equivalent, 44%) at current market prices.
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    Steroid bioconversion in a microemulsion system (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1210-1217 
    Details
    ISSN: 0006-3592
    Keywords: Δ1,2-dehydrogenation of high steroid concentrations ; microemulsion system ; enzyme kinetics ; biphasic system ; stability in ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Δ1,2-dehydrogenation of high concentrations of the steroid -methyl-Reichstein's compound S-21-acetate (16MRSA) in a microemulsion system was studied using heat-dried and thawed Arthrobacter simplex cells as biocatalyst. The microemulsion system consists of an organic phase [75-95% (v/v)] with steroid (1-60 g/Ltot), an aqueous phase [5-25% (v/v)] containing the cells (5-30 g/Ltot), and a neutral surfactant (5-20 g/L organic solvent). Benzene derivatives, which solubilize 16MRSA up to 94 g/L, and phospholipids were used as organic solvents and surfactants, respectively, and menadione was added as an external electron acceptor. Factors affecting the dehydrogenation rate in the microemulsion system were studied. The influences of the 16MRSA and the menadione concentration on the dehydrogenation rate were described by Michaelis-Menten kinetics, apparent V′max and K′m values of 2.06 g/g dry weight h and 18.9 g/L for 16MRSA and 4.97 g/g dry weight h and 1.91 g/L for menadione being obtained. Optimal menadione concentration was dependent on the steroid concentration was dependent on the steroid concentration used. The reaction was strongly inhibited by high product concentrations. Much higher activities were obtained with the thawed cells than with the dried cells, conversions of 98% being reached within 14-16 h. for 16MRSA and cell dry weight concentrations of 40 and 10 g/L, respectively. Activity retention in a batch stirred tank reactor remained constant during the first 16-24 h of operation and then decreased, depending on the stirring rate; 22 to 65% of the initial reaction rate was obtained after 48 h at stirring rates of 650 and 2000 rpm, respectively.
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    Effects of Carbon dioxide on the Rheological behavior and oxygen transfer in submerged penicillin fermentations (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1223-1232 
    Details
    ISSN: 0006-3592
    Keywords: penicillin fermentation ; carbon dioxide effect ; oxygen transfer ; oxygen diffusion ; rheological behavior ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fermentations of Penicillium chrysogenum have been made with different CO2 contents in the influent gas streams. The rheological behavior of the culture broth was found to be significantly changed by exposure to high levels of CO2. This is attributed to the wide variation in the morphology of P. chrysogenum, from normal mycelia with long hyphae to roughly spherical pellets when subjected to high levels of CO2. A correlation has been developed relating volumetric O2 transfer coefficients, kLa, with the effective O2 diffusion coefficients, De, and the apparent viscosities, μapp, based on the results obtained in this study. The use of CO2 as a potent means for altering the rheological properties of culture broths and consequently improving the O2 transfer capabilities in penicillin fermentations was clearly demonstrated.
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    Protein extraction by reverse micelles: A study of the factors affecting the forward and backward transfer of α-chymotrypsin and its activity (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 1239-1246 
    Details
    ISSN: 0006-3592
    Keywords: protein extraction ; α-chymotrypsin ; micelles ; reverse ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: α-chymotrypsin is taken as a model protein to investigate three aspects of the protein extraction by reverse micelles: (1) the comparison between the two forward transfer techniques, i.e., the liquid-liquid and the solid state-liquid transfer; (2)the back-transfer, i.e., the capability of the protein to be recovered from the micellar solution; and (3) the maintainance of the enzyme activity at the end of the extraction cycle. Concerning the forward transfer from the liquid phase, we study first the effect of salt initially present in the aqueous phase on the equilibrium concentration of the extracted species; further, we study the forward protein extraction from the solid state, and the effect of pH, salt, and protein concentration on the transfer efficiency. Concerning the back transfer, we find the somewhat surprising result, that the percentage of protein back-extraction depends on the type and concentration of salt used for the forward transfer. Preliminary data concerning an alternative method for the back-transfer using silica gel to liberate the protein from the micellar environment, are presented. Finally, it is found that the enzyme activity depends again on the type and concentration of salt used for the forward transfer.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991) 
    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.260381101
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    Calcium and phosphate effects on growth and alkaloid production in Coffea arabica: Experimental results and mathematical model (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 859-868 
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    ISSN: 0006-3592
    Keywords: Coffea arabica ; calcium ; phosphate ; cell growth ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plant, mammalian, and microbial cells are commonly immobilized in calcium alginate gels for the production of valuable secondary metabolites. However, calcium ions are known to inhibit growth in various types of cells, and calcium is an integral part of such gels. Therefore, an investigation was conducted to evaluate the effect of calcium on the growth and alkaloid production of a model cell-line, Coffea arabica, in suspension culture before, attempting to immobilize such cells in alginate. A kinetic model was then developed from the results to describe cell growth and alkaloid production and the mechanism by which calcium influences these variables. In addition, it was observed that there was a characteristic relationship between the concentration of calcium in the external medium and the concentration of extra cellular and intracellular phosphate. The intracellular phosphate level was, in turn, related to the production of alkaloids. Using these results, a dynamic mathematical model of cell growth and alkaloid production was developed based on the proposed roles of calcium and phosphate. The model showed satisfactory agreement with three sets of experiments at different calcium concentrations. A possible linkage between the calcium and phosphate results is postulated based on the limited solubility of calcium phosphate.
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    Measuring kLa with randomly pulsed dynamic method (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 889-893 
    Details
    ISSN: 0006-3592
    Keywords: oxygen transfer coefficient ; kLa ; pulsed dynamic method ; mechanically agitated vessels ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This reports on the determination of the overall oxygen transfer coefficient in a mechanically agitated vessel using a randomly pulsed dynamic method. This method consists in exciting the system by randomly switching the inlet gas stream with air or nitrogen with an identical volumetric flow rate. A pseudo-random binary sequence was used. This procedure is routinely used in process control for the identification of system's transfer function. The pulsed dynamic method gives good reliability (as compared with the traditional gassing-out method) and reproducibility in water. However, further improvement is needed before it can be used to monitor on-line the kLa during a fermentation.
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    Transient response method for evaluating the rate constants of reactions over immobilized enzymes (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 922-926 
    Details
    ISSN: 0006-3592
    Keywords: transient response method ; rate constants ; immobilized enzyme ; glucose oxidation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transient response method was utilized to evaluate the rate constants of reaction over immobilized enzyme. Glucose oxidation catalyzed by the immobilized glucose oxidase in a fixed-bed reactor was selected as an example. A theoretical model including the effects of axial dispersion, film diffusion, and intraparticle diffusion was established for the reactor. The individual rate constant of each elementary step of this enzymatic reaction was determined through direct fitting of the experimental response data to the model.
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    Semicontinuous enzymatic hydrolysis of lignocelluloses (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 948-954 
    Details
    ISSN: 0006-3592
    Keywords: cellulase ; cellulose hydrolysis ; steam treatment ; ultrafiltration ; enzyme adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lignocelluloses (steamed hardwood and hardwood kraft pulp) were semicontinuously hydrolyzed on a large scale [2-2. 5 kg of substrate vs. 20, 000 IU filter paperase (FPase)] using a 10-L hydrolysis reactor with an ultrafiltration unit for the recovery and reuse of cellulases. The substrate was added to the reactor at appropriate intervals to keep a concentration of approximately 5% (w/v). All of the enzyme was added at the beginning and no further addition was done. The ultrafiltration unit was operated intermittently rather than continuously due to its enough capacity (dilution rate of 2.5 h-1) and making the enzyme durable. The enzyme required to produce one gram of reducing sugar in this reactor was 27.3 FPase IU/g RS for steamed hardwood and 7.4 FPase IU/g RS for hardwood kraft pulp. The sugar composition of hydrolyzate was unaltered virtually from beginning to end of the hydrolysis in spite of the progressive loss of enzyme activities. The analysis of the enzyme composition in the hydrolyzate during hydrolysis revealed that an exo-β-D-glucanase component was adsorbed selectively at the stages of advanced hydrolysis extent.
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    Growth, death, and oxygen uptake kinetics of Pichia stipitis on xylose (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 973-980 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pichia stipitis NRRL Y-7124 has potential application in the fermentation of xylose-rich waste streams, produced by wood hydrolysis. Kinetic models of cell growth, death, and oxygen uptake were investigated in batch and oxygen-limited continuous cultures fed a rich synthetic medium. Variables included rates of dilution (D) and oxygen transfer (K1a) and concentrations of xylose (X), ethanol (E), and dissolved oxygen (Cox). Sustained cell growth required the presence of oxygen. Given excess xylose, specific growth rate (μ) was a Monod function of Cox. Specific oxygen uptake rate was proportional to μ by a yield coefficient relating biomass production to oxygen consumption; but oxygen uptake for maintenance was negligible. Thus steady-state COX depended only on D, while steady-state biomass concentration was controlled by both D and K1a. Given excess oxygen, cells grew subject to Monod limitation by xylose, which became inhibitory above 40 g/L. Ethanol inhibition was consistent with Luong's model, and 64. 3 g/L was the maximum ethanol concentration allowing growth. Actively growing cells died at a rate that was 20% of μ. The dying portion increased with E and X.
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    Elmer L. Gaden, Jr., father of biochemical engineering (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 995-997 
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    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.260371102
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    Tubular bioreactors: Case study of bioreactor performance for industrial production and scientific researchThe experimental work of this article granted by the Austrain Ministry of Science and Research together with the MF Andritz AG in Graz (1987-1990) and 1991-1992 (FFWF project No. 7695). (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1054-1065 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Application of bioreactors is dominated by industrial production with the consequence that bioreactors also for scientific purposes are mainly used following an empiric pragmatic approach. For the sake of a breakthrough in biotechnology in general, and especially for advanced process development, a more systematic approach is emphasized here. This methodology in bioreactor performance studies is explained and the meaning clarified in a case study of a new type of tubular bioreactor. The central role of so-called “model bioreactors” in bench-scale applications is illustrated as a powerful contribution to the optimal design of bioreactors in technical scale. Pilot plant data in case of a tubular reactor for the production of ethanol with Zymomonas and biopesticides with Bacillus thuringiensis are presented.
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    Kinetic study of hybridoma cell growth in continuous culture. I. A model for non-producing cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 55-64 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetic behavior of a nonproducing hybridoma clone AFP-27-NP was investigated in continuous culture under glucose-limited conditions. A total of more than 21, 000 h of cultures were operated at dilution rates ranging from 0.01 to 0.06 h-1. The viable cell concentrations, dead cell concentrations, and cell volumes all varied with the dilution rate. A steady-state model was developed based on the biomass concentration and the glucose concentration. The specific growth rate as a function of glucose concentration is described by a model similar to the Monod model with a threshold glucose concentration and a minimum specific growth rate incorporated; the model is meaningful only at glucose concentrations and specific growth rates above these levels. A death rate is included in the model which is described by an inverted Monod-type function of glucose concentration. The yield coefficient based on glucose is constant in the lower range of specific growth rates and changes to a new constant value in the upper region of specific growth rates. No maintenance term for glucose consumption was needed; in the plot of specific glucose consumption rate vs. specific growth rate, the line intercepted the specific growth rate axis at a value close to the minimum growth rate. The values for the model parameters were determined from regression analysis of the steady-state data. The model predictions and experimental results fit very well.
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    Simultaneous saccharification and fermentation of cellulose to lactic acid (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 93-96 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recent interest in the industrial manufacture of ethanol and other organic chemicals from biomass has led to the utilization of surplus grain and cane juice as a fermentation feedstock. Since those starting materials are also foods, they are expensive. As an alternative, cellulosic substances - the most abundant renewable resources on earth1 - have long been considered for conversion to readily utilizable hydrolyzates.2, 3For the production of ethanol from cellulose, we have proposed the simultaneous saccharification and fermentation (SSF) process.4 In SSF, enzymatic cellulose hydrolysis and glucose fermentation to ethanol by yeast proceed simultaneously within one vessel. The process advantages - reduced reactor volume and faster saccharification rates - have been confirmed by many researchers.5-8 During SSF, the faster saccharification rates result because the glucose product is immediately removed, considerably diminishing its inhibitory effect on the cellulase system.9To effectively apply the SSF method to produce substances fermented from glucose, several conditions should be satisfied. One is coincident enzymatic hydrolysis and fermentation conditions, such as pH and temperature. The other is that cellulase inhibition by the final product is less than that by glucose and/or cellobiose. One of us has reported that acetic acid, citric acid, itaconic acid, α-ketoglutaric acid, lactic acid, and succinic acid scarcely inhibit cellulase.10 This suggests that if the microorganisms which produce these organic acids were compatible with cellulase reaction conditions, the organic acids could be produced efficiently from cellulosic substrates by SSF.In this article, the successful application of SSF to lactic acid production from cellulose is reported. Though there have been several reports of direct cellulose conversion to organic acids by anaerobes such as Clostridium, only trace amounts of lactic acid were detected in the fermentation medium among the low-molecular-weight fatty acid components.11-13 Lactic acid is one of the most important organic acids and has a wide range of food-related and industrial applications.
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    Lewis cell studies to determine reactor design data for two-liquid-phase bacterial and enzymic reactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 133-140 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Substrate transfer rates from organic to aqueous phases were measured in the presence and absence of biocatalyst in the reaction medium, using modified Lewis cells. These measurements, in combination with intrinsic aqueous phase biocatalytic reaction kinetics, were used to confirm that benzyl acetate hydrolysis by pig liver esterase and toluene oxidation by a strain of Pseudomonas putida occur uniformly throughout the bulk of the aqueous phase. Such data may be used to provide a basis for two-liquid-phase biocatalytic reactor design.
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    Modeling of enzyme-potentiometric sensors involving acid- or base-forming reactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 160-176 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enzyme-potentiometric sensors in which the chemical conversion of the analyte leads to the formation of an acid and/or a base can often display complex response characteristics. In these sensors, the, electrochemically monitored species is usually the H+ ion (pH-based sensors). However, in some cases the conjugate-ion of the H+ (or OH-) ion of the acid (or base) produced-can also be monitored - a specific example being the urease-NH4+ sensor. The response of both types of sensors is strongly affected by: (1) the degree of dissociation of the products and their transport properties in the enzymic film, (2) the amounts of pH-buffers present in the test solution, (3) the test solution's pH, and (4) the diffusion coefficients of the various species. In this article, a previously developed theoretical model for pH-based sensors - in which the differences in diffusivities of the various species were ignored - is generalized to accommodate for such differences, and extended to the latter of the above two types of sensors. It is shown that when the sensor operates under analyte diffusion-controlled conditions, the response of either type of sensor can be predicted by a simple algebraic equation which is independent of the actual kinetics of the enzymic reaction.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    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.260370301
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    An approach for the stable immobilization of proteins (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 227-237 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An approach is presented for the stable covalent immobilization of proteins with a high retention of biological activity. First, chemical modification studies were used to establish enzyme structural and functional properties relevant to the covalent immobilization of an enzyme to agarose based supports. Heparinase was used as a model enzyme in this set of studies. Amine modifications result in 75-100% activity loss, but the effect is moderated by a reduction in the degree of derivatization. N-hydroxysuccinimide, 1,1,1-trifluoroethanesulfonic acid, and epoxide activated agarose were utilized to determine the effect of amine reactive supports on immobilized enzyme activity retention. Cysteine modifications resulted in 25-50% loss in activity, but free cysteines were inaccessible to either immobilized bromoacetyl or p-chloromercuribenzoyl groups. Amine reactive coupling chemistries were therefore utilized for the covalent immobilization of heparinase. Second, to ensure maximal stability of the immobile protein-support linkage, the identification and subsequent elimination of the principal sources of protein detachment were systematically investigated. By using high-performance liquid chromatography (HPLC), electrophoresis, and radiolabeling techniques, the relative contributions of four potential detachment mechanisms - support degradation, proteolytic degradation, desorption of noncovalently bound protein, and bond solvolysis - were quantified. The mechanisms of lysozyme, bovine serum albumin, and heparinase leakage from N-hydroxysuccinimide or 1,1,1-trifluoroethanesulfonic acid activated agarose were elucidated. By use of stringent postimmobilization support wash procedures, noncovalently bound protein loss. An effective postimmobilization washing procedure is presented for the removal of adsorbed protein and the complete elimination of immobilized protein loss.
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    Comparative studies of physiological and environmental effects on the production of cyclosporin A in suspended and immobilized cells of Tolypocladium inflatum (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 256-265 
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    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Process improvement of the production of cyclosporin A (Cy A), a powerful immunosuppressive fungal metabolite, has been undertaken by analyzing suspended and immobilized cell cultures in parallel. Conidiospores of the producer microorganism, Tolypocladium inflatum, were entrapped into porous celite particles. Easier germination of the entrapped spores and more active growth of the immobilized cells were manifested when compared with free cell cultures initiated with spores or with mycelial inocula. Significant differences in precursor flow between the immobilized and free cell systems were evident when the effects of L-valine (a constituent amino acid of the Cy A molecule) on Cy A biosynthesis were compared in the two systems. For the freely suspended cells, L-valine supplemented early in the fermentation served as a possible precursor or stimulator of Cy A biosynthesis. A significant increase in specific production and Cy A yield on carbon source was observed in this system relative to suspended cultures supplemented with L-valine during or after exponential growth. In contrast to the free cell cultures, the addition of L-valine during the initial stage of immobilized cell growth had a negative effect on Cy A production but resulted in somewhat increased cell growth. This suggests an incompatibility between primary and secondary metabolic networks involved in Cy A biosynthesis in the immobilized state upon external addition of the amino acid.
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    The influence of temperature on a mouse-mouse hybridoma growth and monoclonal antibody production (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 292-295 
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    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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    Influence of dilution rate and induction of cloned gene expression in continuous fermentations of recombinant yeast (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 309-317 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of growth rate on cloned gene product synthesis in recombinant Saccharomyces cerevisiae have been studied in continuous culture. The plasmid employed contains a yeast GAL10-CYC1 hybrid promoter directing expression of the E. coli lacZ gene. β-Galactosidase production was therefore controlled by the yeast galactose regulatory circuit, and the induction process and its effects were studied at the various dilution rates. At all dilution rates plasmid stability decreased with induction of lacZ gene expression. In some instances, two induced “steady states” were observed, the first 10-15 residence times after induction and the second after 40-50 residence times. The second induced steady state was characterized by greater biomass concentration and lower β-galactosidase specific activity relative to the first induced “steady-state.” β-Galactosidase specific activity and biomass concentration increased as dilution rate was reduced, and despite lower flow rate and plasmid stability, overall productivity (activity/L/hr) was substantially higher at low dilution rate. Important factors influencing all of the trends were the glucose and galactose (inducer) concentrations in the vessel and inducer metabolism.
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    Performance of the anaerobic baffled reactor under steady-state and shock loading conditions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 344-355 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The anaerobic baffled reactor (ABR) contains a granulated, mixed anaerobic culture segregated into compartments. Operation of four reactors under a range of hydraulic retention times showed that this novel reactor design offers highly efficient performance in the conversion of carbon in the feed stream to methane and carbon dioxide. The design parameter varied was the number of compartments. COD removal at 20 h retention time was routinely over 95% in all reactors, with low washout of biomass. Very high specific reaction rates were achievable (although with a loss of efficiency) at low biomass concentrations and high loading rates. In order to optimize volumetric reaction rates, a tradeoff has to be made between high biomass concentration, granule size, and the resulting mass transfer limitations. Formate is shown to be an important intermediate in the process under conditions of high loading.
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    Different modes of hydrocarbon uptake by two Pseudomonas species (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1-11 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mode of n-hexadecane uptake by two organisms - Pseudomonas M 1 and Pseudomonas N 1 - was studied. During the growth of Pseudomonas M 1 on n-hexadecane, no extracellular biosurfactant/bioemulsifier was produced, no significant n-hexadecane pseudosolubilization was observed, and the reduction of surface and interfacial tensions in the cell-free culture broth was negligible. EDTA, a known inhibitor of hydrocarbon pseudosolubilization, did not inhibit the growth of the organism on n-hexadecane. Normal hexadecane-grown cells showed strong surface-active properties and capacity to adhere firmly to hydrocarbon phase. It was concluded that in this organism, surface-active properties of the cells facilitate attachment of cells to the hydrocarbon-water interface generated by agitation, and promote substrate uptake and growth; no hydrocarbon pseudosolubilization or extracellular mediator is involved in the substrate uptake. Pseudomonas N 1 grew on n-hexadecane much faster than Pseudomonas M 1. Growth of this organism on n-hexadecane was associated with the extracellular production of biosurfactant-bioemulsifier and n-hexadecane pseudosolubilizing factor; the growth was strongly inhibited by 5 mM EDTA, indicating that hydrocarbon pseudosolubilization was the dominant factor in substrate uptake. The rate of n-hexadecane pseudosolubilization was high enough to account for the substrate up take rate. Hydrocarbon emulsifying and n-hexadecane pseudosolubilizing factors were isolated and tentatively characterized as lipoprotein and glycoprotein, respectively. Both factors act in a synergistic manner to provide enhanced hydrocarbon transport to cells through pseudosolubilization. It is proposed that this facility of mediated hydrocarbon transport is the basis for the relatively fast rate of growth of Pseudomonas N 1 on hydrocarbon.
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    A model for mercuric ion reduction in recombinant Escherichia coli (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 47-54 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plasmid-encoded mercuric reduction involves transfer of Hg2+ across the cellular envelope and reduction to Hg0 by the cytoplasmic mercuric reductase using NADPH. A mathematical model was developed for the binding and transfer of Hg2+ by transport proteins and the subsequent reduction of Hg2+. The values of the model parameters were determined using experimental data. The derived rate expressions were similar to the previously experimentally determined ones. The model predicted that a differential amplification of the transport protein relative to mercuric reductase expression levels may enhance the Hg2+ reduction rate in whole cells.
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    Masthead (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991) 
    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.260370201
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    A dispersion model for predicting the extent of starch liquefaction by Bacillus licheniformis α-amylase during reactive extrusion (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 681-690 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Baker-Perkins corotating twin screw extruder was used as a bioreactor to hydrolyze pregelantinized corn starch by themophilic Bacillus licheniformis α-amylase. The extruder was modeled as a tube, and characterized as a closed system. This characterization is not in the thermodynamic sense; rather, it relates to the profile of a tracer fluid upon entry to and exit from the reaction zone. The reaction kinetics were modeled by a modified first-order equation, which allowed the dispersion equation to be solved analytically with the Danckwerts boundary condition. Data from several extrusion runs were super-imposed to obtain a profile to evaluate the model. The dispersion number, determined from the first and second moments of the RTD curve, was primarily a function of the length of the reaction zone. There was good agreement between predictions and experimental data, especially at low dispersion numbers. In general, the axial dispersion model appears to be suitable for analysis of enzymatic reactions of up to 30% conversion. At a fixed flow rate and constant temperature, the extent of starch conversion depends significantly on moisture content, residence time and enzyme dosage, but not on screw speed.
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    Calculation of the heat of growth of Escherichia coli K-12 on succinic acid (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 334-343 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using data from the literature, a method is adopted for determining the empirical composition and the unit carbon formula for dried Escherichia coli K-12 cells by summing the quantities of C, H, O, N, P, and S in each of the major classes of macromolecular substances comprising the cellular biomass. With these data and the molar growth yield of cells on succinic acid, equations are written representing the anabolism and catabolism of E. coli K-12 on this quantity of substrate. The enthalpy change accompanying catabolism can be calculated directly using standard enthalpies of formation because there is no term representing cellular substance. The enthalpy change accompanying anabolism is calculated to be very small or zero using microcalorimetric and other data from which the enthalpy of formation of a unit quantity of living cellular substance can be obtained. This indicates that the net enthalpy change accompanying the growth process (anabolism plus catabolism) is the same as that calculated for catabolism alone, in agreement with the same conclusion by several investigators using direct microcalorimetry. The method described here of determining the unit carbon formula and the quantity of ash remaining after cellular combustion is compared to that conventionally used in which cellular P and S is considered either to be negligible or to be a part of the ash. It is concluded that equations representing anabolism and the growth process can be written more accurately using the presently described method, leading to more accurate thermodynamic calculations.
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    Rate equations for the vigorous stationary phase fermentation of citric acid by Saccharomycopsis lipolytica (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 985-988 
    Details
    ISSN: 0006-3592
    Keywords: Saccharomycopsis lipolytica ; rate equations ; fermentation ; citric acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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    High gradient magnetic separation of yeast (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1021-1028 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High gradient magnetic separation (HGMS) is used to separate nonmagnetic microorganisms from solution by a technique known as seeding. Fine magnetic particles are adhered to the cells' surfaces, making them magnetic and amenable to magnetic separation. Attachment of the sub-micron, acicular γ-Fe2O3 seed to the yeast surface occurs irrespective of the solution pH and surface charge and is essentially irreversible. A model is developed to predict the separation of yeast in a high gradient magnetic separator. The effective capture radius is assumed to be proportional to the derived magnetic parameter γ for the case where the dominant competing force to magnetic attraction is the magnetic floc's inertia. Using this parameter, yeast separation in an HGMS unit is predicted. The measured separation of Saccharomyces cerevisiae at differing magnetic seed concentrations and two flow rates supports the above model.
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    Periodic operation of immobilized live cell bioreactor for the production of candicidin (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1010-1020 
    Details
    ISSN: 0006-3592
    Keywords: immobilized cells ; periodic operation ; secondary metabolites ; simulation ; candicidin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A lumped model for cell growth and secondary metabolite production in an immobilized live cell bioreactor has been developed. This model is applied here to simulate the performance of an immobilized bioreactor under steady-state conditions and under conditions of periodically varying concentration of a growth-limiting substrate. The results of the simulation study were experimentally verified in the case of the production of the antibiotic candicidin by Streptomyces griseus in an immobilized bioreactor with forced periodic operation. The results of the studies suggest that periodically operated immobilized live cell bioreactors can provide a potent alternative for the production of non-growth-associated biochemicals, as compared to free cell fermentations, pulsed fermentations with process cycle regeneration, and nonregenerated bioreactors. This work has demonstrated that by frequent pulsing of the growth limiting nutrient, stable extended production can be obtained at high specific cellular productivities.
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    Use of fluorometry for monitoring and control of a bioreactor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1043-1049 
    Details
    ISSN: 0006-3592
    Keywords: Multiple excitation fluorometric system (MEFS) ; NADH probe ; culture fluorescence ; inner filter effects ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new fluorescent bioreactor monitoring probe - multiple excitation fluorometric system (MEFS) - has been developed. This probe was compared to the commercially available BioChem Technology FluroMeasure system (NADH probe). In this task the fluorescence behavior of three model fermentation systems, ethanol fermentation by Candida utilis, phenol fermentation by Pseudomonas putida, and glucose fermentation by Saccharomyces cerevisiae, were examined. The results indicated that the fluorescence intensity and behavior of various cellular fluorophors vary significantly between the different fermentation systems. Monitoring a fermentation process using only NAD(P)H fluorescence provided limited information. The NAD(P)H fluorescence was found not to be the best fluorescence signal for monitoring cell concentrations. The best way of monitoring a bioreactor by fluorometry may be to monitor several fluorophors in the whole culture broth simultaneously and to relate these fluorescence signals to various biological parameters.
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    Optimization of batch processes involving simultaneous enzymatic and microbial reactions (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1087-1094 
    Details
    ISSN: 0006-3592
    Keywords: fermentation ; optimization ; enzymatic reactions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two general models for batch simultaneous enzymatic and microbial reaction (SEMR) processes are presented, the second derived from and simpler than the first and accounting for enzyme denaturation. Using the second model and parameter values from the literature, simulation was used to examine a range of enzyme addition rate strategies (in which the rate was a linear function of time) for a relatively fast ethanol fermentation and for a longer duration citric acid fermentation, both using cellulose as the substrate. For the ethanol process it is optimal (for a specific objective function which accounts for product value and enzyme cost) to add all the enzyme at the beginning of the process. But for the citric acid process a linearly decreasing enzyme addition rate, coupled with the addition of a small fraction of the enzyme at time zero, is better than pure batch operation or operation with the best constant enzyme feed rate.
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    Development of a large-scale continuous substrate feed process for the biotransformation of simvastatin by Nocardia s.p. (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 1101-1107 
    Details
    ISSN: 0006-3592
    Keywords: simvastatin ; microbial ; hydroxylation ; fermentation ; biotransformation ; scale-up ; dissolved oxygen ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article describes a process for microbial hydroxylation of simvastatin by a Nocardia sp. Simvastatin (Zocor) belongs to the family of HMGCoA reductase inhibitors used as cholesterol-lowering drugs. Studies at 14 L scale showed that high substrate (simvastatin) concentrations inhibited product formation; consequently, continuous slow feeding of the substrate was introduced to maintain low residual simvastatin concentrations. Dissolved oxygen levels above 50% air saturation were desirable for the biotransformation. The process was scaled up to 19,000-L fermentors using an on-line filter sterilization system for substrate feeding. The feed rate was regulated by off-line high-pressure liquid chromatography (HPLC) assays to keep the substrate concentration below 20 mg/L. Intermittent addition of nutrients helped to boost the bioconversion rate to give final titers of 400 mg/L 6-β-hydroxymethyl simvastatin. Enrichment of the nutrient medium led to bioconversion titers of 800 mg/L 6-β-hydroxymethyl simvastatin. Bioconversion efficiencies (desired product/substrate) of 22-25% with a ratio of desired product/side products of 0.7 were obtained by this process.
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    Structured modeling of a microbial system: II. Experimental verification of a structured lactic acid fermentation model (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 11-23 
    Details
    ISSN: 0006-3592
    Keywords: lactic acid fermentation ; fermentation ; microbial fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A two-compartment model for the lactic acid fermentation with Streptococcus cremoris is experimentally verified. The seven parameters of the model are determined using steady-state chemostat data at varying values of dilution rate, D, but with a constant feed concentration, sf, of a single carbohydrate source (glucose, lactose, or galactose), and a constant feed concentration of sNf of the N source. Steady-state measurements of the RNA content at different exit concentrations, s, of the carbohydrate are included to calculate kinetic parameters that determine the cell composition for varying operating conditions. The model is tested using data from a large set of steady-state and non-steady-state experiments: batch fermentations and step and pulse experiments in a chemostat. Both qualitatively and quantitatively the major features of the model are confirmed: the external substrates enter into intracellular high-energy building blocks, and lactic acid is formed as a by-product of these reactions. Cell growth depends on the fraction of active components (XA) of the cell and is not accompanied by lactic acid production. Possible model modifications are discussed, primarily to obtain a better description of lactic acid fermentation at nongrowth conditions.
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    Characterization of a pilot plant airlift tower loop reactor: III. Evaluation of local properties of the dispersed gas phase during yeast cultivation and in model media (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 56-64 
    Details
    ISSN: 0006-3592
    Keywords: bioreactor ; tower loop bioreactor ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The local properties of the dispersed gas phase (gasholdup, bubble diamater, and bubble velocity) were measured and evaluated at different positions in the riser and downcomer of a pilot plant reactor and, for comparison, in a laboratory reactor. These were described in Parts I and II of this series of articles during yeast cultivation and with model media. In the riser of the pilot plant reactor, the local gas holdup and bubble velocities varied only slightly in axial direction. The gas holdup increased considerably, while the bubble velocity increased only slightly with aeration rate. The bubble size diminished with increasing distance from the aerator in the riser, since the primary bubble size was larger than the equilibrium bubble size. In the downcomer, the mean bubble size was smaller than in the riser. The mean bubble size varied only slightly, the bubble velocity was accelerated, and the gas holdup decreased from top to bottom in the downcomer. In pilot plant at constant aeration rate, the properties of the dispersed phase were nearly constant during the batch cultivation, i.e., they depended only slightly on the cell concentration. In the laboratory reactor, the mean bubble sizes were much larger than in the pilot plant reactor. In the laboratory reactor, the bubble velocities in the riser and downcomer increased, and the mean gas holdup and bubble diameter in the downcomer remained constant as the aeration rate was increased.
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    Dilution rate as a determinant of mycelial morphology in continuous culture (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 38 (1991), S. 75-81 
    Details
    ISSN: 0006-3592
    Keywords: mycelial morphology ; Fusarium graminearum ; mycoprtein ; continuous culture ; chemostat ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The morphology of mycelial fungi in liquid culture effects culture rheology and this in turn may affect product yield. It is therefore important to understand how environmental factors influence mycelial morphology and this paper describes the effect of dilution rate on two strains of Fusarium graminearum, the relatively sparsely branched parental strain (A3/5) and a relatively highly branched “colonial” variant (C106). At any given dilution rate, the concentration of mycelial fragments present at steady state of both strains remained approximately constant with time, suggesting that mycelial fragmentation occurred in a regular manner. However, for both strains fragment concentration decreased with increasing dilution rate. The strains had a similar morphology at a dilution rate of 0.07 h-1. The length of the hyphal growth unit of A3/5 increased with increase in dilution rate, while that of C106 decreased with increase in dilution rate. At all dilution rates, C106 produced up to ten times more macroconidia than A3/5.
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    Studies on the optimization of growth and indole alkaloid production by hairy root cultures of Catharanthus roseus (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 673-680 
    Details
    ISSN: 0006-3592
    Keywords: indole alkaloid production ; Catharanthus roseus ; Agrobacterium rhizogenes ; hairy root cultures ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Catharanthus roseus hairy root cultures, genetically transformed with Agrobacterium rhizogenes, produce a wide variety of indole alkaloids. The effect of sucrose, phosphate, nitrate, and ammonia concentrations on growth and indole alkaloid production of C. roseus hairy root cultures were studied by using statistical experimental designs and linear regression analysis. Contradictory effects of these nutrients on growth and indole alkaloid production were found. The maximal growth was obtained by having 77. 8 mg NaH2PO4 · H2O/L and 1. 311 g KNO3/L in the medium, whereas the specific production of alkaloids was highest at the lowest levels of all the nutrients studied. The maximal dry weight was obtained with high values of sucrose and ammonia, but clear optimum concentrations could not be found. When having enough nutrients to support reasonable growth, it appeared difficult to affect the specific alkaloid production rates considerably. The growth (dry wt.) with the optimized nutrient concentrations in the medium was more than 50% better than in the control medium with about the same alkaloid production.
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    The pH mediated effects of initial glucose concentration on the transitory occurrence of extracellular metabolites, gas exchange, and growth yields of aerobic batch cultures of klebsiella pneumoniae (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 696-696 
    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.260370713
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    The production of the enzyme dextransucrase using nonaerated fermentation techniques (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 703-707 
    Details
    ISSN: 0006-3592
    Keywords: Dextransucrase ; Leuconostoc mesenteroides ; fermentation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High yields of the enzyme dextransucrase have been produced repeatedly by fed-batch fermentation techniques. Activities in excess of 21.9 U/cm3 have been obtained by culturing Leuconostoc mesenteroides NRRL B-512(F) under nonaerated fed-batch fermentation conditions. Aerobic fermentations carried out under identical conditions have consistently produced enzyme of less than 17 U/cm3, but with no difference in the final cell concentration in the broth. Different types of yeast extract have been found to have significant effect on the final cell concentration and more especially on the enzyme activity with enzyme yields varying by as much as 50% when different types of yeast extracts were used.
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    Retention of enzyme by electropolymerized film: A new approach in developing a hypoxanthine biosensor (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 729-735 
    Details
    ISSN: 0006-3592
    Keywords: amperometric biosensor ; hypoxanthine ; electropolymerization ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An amperometric biosensor for hypoxanthine was constructed by forming a layer of crosslinked xanthine oxidase on a platinum electrode, followed by electropolymerization of a submonolayer film of resorcinol and para-diaminobenzene. The fabricated electrodes were evaluated for speed of response, sensitivity, and reusability. Optimal performance was obtained with enzyme-based electrodes sparsely covered with film which was formed by electropolymerization in less than 6 min. The resulting electrodes exhibited linear response to hypoxanthine in the. range 5-300 μM with a response time of 2 min. Application of the biosensor in monitoring hypoxanthine content of fish extracts yielded results which agreed well with spectrophotometric assays using soluble xanthine oxidase. The biosensor was stable for 60 days when stored at 4°C in phosphate buffer and it could be used continuously for 6 h with over 50 assays.
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