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  • Biochemistry and Biotechnology  (3,454)
  • ddc:330
  • 1995-1999  (3,547)
  • 1955-1959  (39)
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  • 101
    Electronic Resource
    Electronic Resource
    Comparison of hydrolysis and esterification behavior of Humicola lanuginosa and Rhizomucor miehei lipases in AOT-stabilized water-in-oil microemulsions: II. Effect of temperature on reaction kinetics and general considerations of stability and productivity (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 190-196 
    Details
    ISSN: 0006-3592
    Keywords: hydrolysis ; esterification ; Humicola lanuginosa ; Rhizomucor miehei ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Humicola lanuginosa lipase (HIL) and Rhizomucor miehei lipase (RrnL), isolated from commercial preparations of Lipolase and Lipozyme, respectively, were solubilized in AOT-stabilized water-in-oil (w/o) microemulsions in n-heptane and aspects of their hydrolysis and condensation activity examined. The temperature dependence of HIL hydrolysis activity in unbuffered R = 10 microemulsions matched very closely that for tributyrin hydrolysis by Lipolase in an aqueous emulsion assay. Apparent activation energies were measured as 13 ± 2 and 15 ± 2 kJ mol / respectively. Condensation activity, however, was essentially independent of temperature over the range 5° to 37°C. The stability of HIL over a 30-day period was very good at all pH levels (6.1, 7.2, 9.3) and R values studied (5, 7.5, 10, 20), except when high pHs and low R values were combined. The excellent stability was reflected by the linearity of the productivity profiles which facilitate system optimization. The temperature dependence of RmL hydrolysis activity toward pNPC4 showed a maximum at 40°C and an apparent Eact = 20 ± 2 kJ mol-1 was calculated based on the linear region of the profile (5° to 40°C). RmL esterification activity showed only a slight dependence on temperature over the studied range (0° to 40°C) and an apparent Eact = 5 ± 1 kJ mol-1 was measured for octyl decanoate synthesis. Both RmL and HIL, therefore, have potential for application in low temperature biotransformations in microemulsion-based media. The stability of RmL over a 30-day period was good in R = 7.5 and R = 10 microemulsions containing pH 6.1 buffer, and this was reflected in the linearity of their respective productivity profiles. RmL stability was markedly poorer at more alkaline pH, however, and proved to be sensitive to relatively small changes in the R value. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480304
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  • 102
    Electronic Resource
    Electronic Resource
    Enzymatic preparation of biosurfactants from sugars or sugar alcohols and fatty acids in organic media under reduced pressure (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 214-221 
    Details
    ISSN: 0006-3592
    Keywords: sugar esters ; lipase ; nonaqueous media ; Candida antarctica ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biosurfactants were prepared by enzymatic esterification of sugars and sugar alcohols in nonaqueous media. Sorbitol monooleate was produced in pure molten substrates, with reduced pressure to remove water. The results were compared to synthesis in organic solvent, with and without water removal. Synthesis in organic solvent with water removal, obtained by refluxing through a desiccant under reduced pressure, proved to be the most efficient method in terms of total yield and side-products formation. This process was applied to the production of different surfactants, by changing the nature of the hydrophilic and hydrophobic moieties. Yields above 90% of monoesters were obtained after 24 h when the reaction was carried out in 2-methyl-2-butanol with Novozym 435 (Type B lipase from Candida antarctica) with an excess of hydroxyl donor. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480308
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  • 103
    Electronic Resource
    Electronic Resource
    Kinetics of phase separation for polyethylene glycol-phosphate two-phase systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 246-256 
    Details
    ISSN: 0006-3592
    Keywords: polyethylene glycol ; phosphate ; phase separation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Phase separation times for polyethylene glycol (PEG)-4000-phosphate aqueous two-phase systems were studied, for small scale (5-g) and large scale (1300-g) systems, as a -function of the stability ratio. Profiles of dispersion height for both large and small scale systems were represented as a fraction of the initial height and were found to be independent of the geometrical dimensions of the separator. Furthermore, by plotting time as a fraction of the initial height the total time of separation can be calculated for a given height of system at a particular stability ratio. This generalization is important for the design of large scale aqueous two-phase separators. Phase separation times were also found to be dependent on which of the phases is continuous. A characteristic change in phase separation time was also observed at the phase inversion point (i.e., where the dispersed phase changes to a continuous phase and vice versa) and this point tends toward higher volume ratios as the tie-line length (TLL) is increased. Furthermore, the phase inversion point at each TLL corresponds to a fixed phosphate concentration. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480311
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  • 104
    Electronic Resource
    Electronic Resource
    Hydrodynamic, physiological, and morphological characteristics of Fusarium moniliforme in geometrically dissimilar stirred bioreactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 266-277 
    Details
    ISSN: 0006-3592
    Keywords: Fusarium moniliforme ; hydrodynamics ; image analysis ; kinetic energy ; morphology stirred bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of two mixing geometries (at the same scale) with different flow energy distributions on the performance of the gibberellic acid fermentation and on the morphology of the producing fungus Fusarium moniliforme was investigated. Fermentations were performed using a turbine mixing system (TMS) and a counterflow mixing system (CMS), which were high and low power number mixing systems, respectively. Different agitator speed rate profiles were maintained to obtain equal specific power inputs to both mixing systems. Substantial differences in morphology and productivity of F. moniliforme were found. To investigate the causes of these differences, local values and spectra of the kinetic energy of flow fluctuations were measured during the fermentations using a stirring intensity measuring device (SIMD) and a frequency spectrum analyzer. Biomass and gibberellic acid concentrations were found to be higher in the TMS, where the energy distribution was less even, and Vi/here the main part of the energy was at small frequencies (large eddies). An automated image analysis method was used for quantitative characterization of F. moniliforme freely dispersed mycelia and clump morphology. A higher proportion of clumped mycelia with clumps of larger area, perimeter, and roughness was observed in the TMS. A correlation between the morphology and productivity was found, and TMS favored the development of more productive mycelia with longer and thinner hyphae. Introduced power was not a good parameter to characterize different impellers, even at a given scale. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480313
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  • 105
    Electronic Resource
    Electronic Resource
    Recovery and purification of bioproducts: I (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 301-301 
    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.260480402
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  • 106
    Electronic Resource
    Electronic Resource
    Novel function of guanidine hydrochloride in reverse micellar extraction of lysozyme from chicken egg white (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 333-340 
    Details
    ISSN: 0006-3592
    Keywords: reverse micelle ; guanidine hydrochloride ; extraction ; lysozyme ; chicken egg white ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The efficiency of guanidine hydrochloride (GuHCl) addition in the suppression of gel formation and the extraction of lysozyme during reverse micellar extraction from chicken egg white was investigated. A low concentration of GuHCl in the feed permitted the successful extraction of lysozyme in its native form without gel formation, which is perceived as a novel function of GuHCl. The highest recovery and specific activity of lysozyme were obtained at a GuHCl concentration of 0.06 M in 25 mM AOT reverse micellar extraction from 20-fold-diluted natural chicken egg white. Lysozyme and ovalbumin CD spectra in the corresponding GuHCl aqueous solutions revealed no changes in the higher order structures of the proteins. Furthermore, the specific activity of lysozyme in the feed was well preserved in the GuHCl system. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480406
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  • 107
    Electronic Resource
    Electronic Resource
    Correlation between steady-state cell concentration and cell death of hybridoma cultures in chemostat (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 18-26 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; cell death ; chemostat ; autoinhibitor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the present study, the steady-state cell density (X) of chemostat cultures of murine hybridoma was varied by the concentration of glucose and glutamine in culture medium and the dissolved oxygen partial pressure. Except at low glutamine and low oxygen levels, the specific death rate (kd) of the cultures was found to decrease with increasing dilution rate (D). However, the plot of kd vs. X/D yielded linear relation, which suggests that cell death was due to a non-growth-linked inhibitory product of the cells. The kd value measured at low glutamine and low oxygen levels remained practically unchanged over a wide range of D between 0.020 and 0.029 h-1. The kd for low oxygen cultures was always lower than the values obtained in low glucose and low glutamine cultures. A low-molecular-weight component of possibly less than 3000 MW was detected to be cell-death-inducing in the supernatant of exponentially growing cultures. It was neither lactate nor ammonium. The autoinhibitor was not cell-line specific. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450104
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  • 108
    Electronic Resource
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    On-line gas analysis in animal cell cultivation: I. Control of dissolved oxygen and pH (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 42-53 
    Details
    ISSN: 0006-3592
    Keywords: oxygen uptake rate ; animal cell cultivation ; dissolved oxygen and pH ; state space controller ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To monitor gas reaction rates in animal cell culture at constant dissolved oxygen concentration (DO) and constant pH it was necessary to develop improved control methods. Decoupling of both controllrs was obtained by manipulation of molar fractions of oxygen and carbon dioxide in the gas phase. Two pairs of DO and pH controllers were designed and tested both in simulation and exprimental runs. The first controller pair was developed for headspace aeration only, whereas the second controller pair was designed for bubble aeration using a microsparger and flushing the headspace with helium. pH was controlled by a conventional discrete PID controller in its velocity form. For DO control two linear state space feedback controllers with parameter adaptation were established. In these controllers the oxygen uptake rate (OUR) was considered as a disturbance and was not included in the mathematical model. The feedback gain adaptation was based on the difference between the actual molar fraction of oxygen at time step n and the initial molar fraction. This difference is related to OUR and was used to increase or decrease the state feedback controller gain (k and k1, respectively) in a slow manner. With these controllers it was possible to get an excellent online estimate of OUR. In the case of bubble aeration a simple gas phase mass balance was sufficient, whereas during the headspace aeration a liquid phase balance was required. It has been shown that determination of OUR using gas balance requires a significantly better controller performance compared to just keeping DO and pH within reasonable limits. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450107
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  • 109
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    Parametric sensitivity of stoichiometric flux balance models applied to wild-type Escherichia coli metabolism (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 69-79 
    Details
    ISSN: 0006-3592
    Keywords: E. coli ; linear optimization ; metabolic fluxes ; stoichiometry ; sensitivity analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stoichiometrically based flux balance models provide a method to quantify the metabolic pathway fluxes within a living cell. Predictions of flux balance models are expected to have applications in pathway engineering as well as in bioprocess design and control. These models utilize optimality principles applied to metabolic pathway stoichiometry along with the metabolic requirements for growth to determine the flux distribution in a metabolic network. A flux balance model has been developed for Escherichia coli W3110 using five experimentally determined strain-specific parameters. In this report, we determine the sensitivity of the predictions of the flux balance model to these five strain-specific parameters. Model predictions are shown to be sensitive to the two parameters describing metabolic capacity, while they are relatively insensitive to the three parameters that describe the metabolic requirements for growth. Thus, when stoichiometrically based models are formulated for additional strains one needs to measure the metabolic capacity (maximum rates of nutrient and oxygen utilization) accurately. Determination of metabolic capacity from batch experiments is relatively easy to perform. On the other hand, the harder to determine maintenance parameters need not be as accurately determined. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260450110
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  • 110
    Electronic Resource
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    Rheologies and morphologies of three actinomycetes in submerged culture (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 80-85 
    Details
    ISSN: 0006-3592
    Keywords: rheology ; morphology ; actinomycete ; Saccharopolyspora erythraea ; Actinomadura roseorufa ; Streptomyces rimosus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The broth rheologies and morphologies of three actinomycetes (Saccharopolyspora erythraea, Actinomadura roseorufa, and Streptomyces rimosus) in submerged culture have been examined. The rheology of all the broths became pseudoplastic as soon as significant growth occurred with the power law index, n, falling to 0.20 to 0.25. The consistency index, K, rose with biomass concentration although in some instances it fell later in the fermentation. The mean main hyphal lengths of all cultures were in the range, 15 to 25 μm, and did not alter greatly even when large changes in K were occurring. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450111
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  • 111
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    Synthesis of protein-containing polymers in organic solvents (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 10-17 
    Details
    ISSN: 0006-3592
    Keywords: proteins ; enzymes ; immobilization ; biopolymers ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Subtilisin has been modified with polyethylene glycol (PEG) monomethacrylate (MW 8000) by reductive alkylation, and incorporated into polymethyl methacrylate durring free-radical initiated polymerization. The activity and stability of the PEG-modified enzymes have been determined in aqueous buffer and organic solvents. The Km and Vmax values for unmodified, singly and doubly modified subtilisin were compared in these environments, and the half-lives of both modified enzymes were remarkably high (up to 2 months). The protein-containing polymer was analyzed for activity and polymer properties, and our results indicate that active subtilisin can be incorporated into polymethyl methacrylate during polymerization in organic solvents while retaining its activity and stability. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450103
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  • 112
    Electronic Resource
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    Enzymatic interesterification of triglyceride with surfactant-coated lipase in organic media (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 27-32 
    Details
    ISSN: 0006-3592
    Keywords: esterification ; lipase ; glycerides ; organic solvent ; surfactant ; bioconversion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several surfactant-coated enzymes have been prepared by coating lipases of various origins with a nonionic surfactant, glutamic acid dioleylester ribitol (2C18Δ9GE). Enzymatic interesterification of tripalmitin with oleic acid using the surfactant-coated lipase was carried out in organic media. The surfactant-coated lipases could effectively catalyze the interesterification of glycerides better than did the powder lipases. A suitable organic solvent was an aliphatic hydrocarbon such as isooctane. The enzymatic activity for the interesterification strongly depended on the origin of the lipase. The surfactant-coated lipase prepared by Mucor javanicus showed the highest enzymatic activity for the interesterification of glycerides, although its powder lipase did not show enzymatic activity. Selective interesterification of glycerides could be performed by adjusting the concentration ratio of oleic acid to tripalmitin in isooctane. Di-substituted glyceride could be selectively produced when the concentration ratio of carboxylic acid to glycerides was 7. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450105
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  • 113
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    On-line gas analysis in animal cell cultivation: II. Methods for oxygen uptake rate estimation and its application to controlled feeding of glutamine (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 54-62 
    Details
    ISSN: 0006-3592
    Keywords: oxygen uptake rate ; animal cell cultivation ; hybridoma ; monoclonal antibody ; glutamine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Different methods for oxygen uptake rate (OUR) determinations in animal cell cultivation were investigated using a high quality mass spectrometer. Dynamic measurements have considerable disadvantages because of disturbances of the growing cells by the necessary variations of dissolved oxygen concentration. Only infrequent discrete measurements are possible using this method. Stationary liquid phase balance yielded better results with much higher frequency. Gas phase balancing has the advantage of not requiring dissolved oxygen measurement and knowledge of KLa, both of them are easily biased. It was found that simple gas phase balancing is either very inaccurate (error larger than expected signal) or very slow, with gas phase residence times of several hours. Therefore, a new method of aeration was designed. Oxygen and CO2 transfer are mainly achieved via sparging. The gas released to the headspace is diluted with a roughly 100-fold stream of an inert gas (helium). Through this dilution, gas ratios are not changed for O2, CO2, Ar, and N2. The measurement of lower concentrations (parts per million and below) is easy using mass spectrometry with a secondary electron multiplier. With this new method an excellent accuracy and sufficient speed of analysis were obtained. All these on-line methods for OUR measurement were tested during the cultivation of animal cells. The new method allowed better study of the kinetics of animal cell cultures as was shown with a hybridoma cell line (HFN 7.1, ATCC CRL 1606) producing monoclonal antibodies against human fibronectin. With the aid of these methods it was possible to find a correlation between a rapid decrease in oxygen uptake rate (OUR) and glutamine concentration. The sudden decrease in OUR can be attributed to glutamine depletion. This provided a basis for the controlled addition of glutamine to reduce the formation of ammonia produced by hydrolysis. This control method based on OUR measurement resulted in increased cell concentration and threefold higher product concentration. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450108
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  • 114
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    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.260450201
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  • 115
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    Starvation-induced programmed death of hybridoma cells: Prevention by amino acid mixtures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 86-90 
    Details
    ISSN: 0006-3592
    Keywords: hybridoma ; nutrition ; cell death ; apoptosis ; monoclonal antibody ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Association of the availability of nutrients with the phenomenon of programmed cell death - apoptosis - was investigated using hybridoma cells cultured in protein-free medium under conditions of starvation, i.e., in RPMl-1640 medium diluted to 50% with saline. Amino acid mixtures, such as MEM essential amino acids or MEM nonessential amino acids were found to prevent starvation death significantly when added to the diluted medium in 1 to 2 mM concentrations, the MEM vitamin mixture was ineffective, and glutamine displayed a moderate growth-supporting effect. The specific monoclonal antibody production rate in cultures supplemented with amino acid mixtures was strikingly low, whereas supplementation with glutamine alone or simultaneously with other amino acids resulted in a specific antibody production rate comparable with the rate observed in undiluted medium. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450112
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  • 116
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    On-line calibration of a computerized biosensor system for continuous measurements of glucose and lactate (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 122-128 
    Details
    ISSN: 0006-3592
    Keywords: on-line calibration ; continuous monitoring ; biosensor system ; enzyme reactor ; glucose ; lactate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An on-line calibration procedure for application in continuous monitoring systems has been developed. Control of the calibration value and recalibration on-line during monitoring is possible without having to disrupt the sample withdrawal. The calibration procedure has been applied and evaluated in a continuous biosensor system based on the detection of oxygen depletion during enzymatic substrate conversion by immobilized oxidases. Evaluation included on-line calibration during continuous measurements of glucose and lactate in bovine blood samples. Calibration of the complete system consisting of a sampling device, a sample handling step, a biocatalytic step, a detection step, and a data processing unit is performed by the on-line addition of a calibration solution to a blank sample which is fed through the system. The calibration cycle is completed within 5.5 min. When recalibration is carried out during monitoring, the calibration solution is added to the sample, instead of to a blank sample, and the increase in outlet singl is registered. The major advantage of this internal standard principle is that the calibration solution is fed through the whole system according to the same path as the sample solution and thus takes into account all parameters influencing the sample. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450205
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  • 117
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    Real-time fuzzy-knowledge-based control of Baker's yeast production (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 135-143 
    Details
    ISSN: 0006-3592
    Keywords: baker's yeast; ; knowledge-based system ; fuzzy logic ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A real-time fuzzy-knowledge-based system for fault diagnosis and control of bioprocesses was constructed using the object-oriented programming environment Small-talk/V Mac. The basic system was implemented in a Macintosh Quadra 900 computer and built to function connected on line to the process computer. Fuzzy logic was employed in handling uncertainties both in the knowledge and in measurements. The fuzzy sets defined for the process variables could be changed on-line according to process dynamics. Process knowledge was implemented in a graphical two-level hierachical knowledge base. In on-line process control the system first recognizes the current process phase on the basis of top-level rules in the knowledge-base. Then, according to the results of process diagnosis based on measurement data, the appropriate control strategy is subsequently inferred making use of the lower level rules describing the process during the phase in question. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450207
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  • 118
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    A mathematical model for the leukocyte filtration process (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 158-164 
    Details
    ISSN: 0006-3592
    Keywords: depth filtration ; mathematical model ; leukocyte filtration ; filter efficiency ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Leukocyte filters are applied clinically to remove leukocytes from blood. In order to optimize leukocyte filters, a mathematical model to describe the leukocyte filtration process was developed by modification of a general theoretical model for depth filtration. The model presented here can be used to predict the time-dependent leukocyte filtration as a function of cell-cell interaction in the filter, filter efficiency, filter capacity, filter dimensions, and leukocyte concentration in the suspension applied to the filter. The results of different leukocyte filtration experiments previously reported in the literature could be well described by the present model. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260450210
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  • 119
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    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.260450301
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  • 120
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    A study of mass transfer in yeast in a pulsed baffled bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 165-175 
    Details
    ISSN: 0006-3592
    Keywords: pulsed baffled bioreactor ; baffle ; yeast resuspension ; oscillation ; power density ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We report experimental data of mass transfer of oxygen into yeast resuspension in a pulsed baffled bioreactor. The bioreactor consists of a 50-mm-diameter column with the presence of a series of either wall (orifice) or central (disc) baffles or a mixture of both where fluid oscillation can also be supermposed during the experiments. Air bubbles are sparged into the bottom of the pulsed baffled bioreactor, and the kinetics of liquid oxygen concentration in the yeast solution is followed using a dissolved oxygen probe with a fast response time of 3 s together with the dynamic gassing-out technique. Among the three different baffle geometries investigated, the orifice baffles gave the highest and sharpest increase in the oxygen transfer rate, and the trends in the kLa measurements are consistent with the fluid mechanics observed within both the systems and previous work. In addition, we have also compared the kLa values with those obtained in a stirred tank; an 11% increase in the KLa is reported. © 1995 John Wiley & Sons, Inc.
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    Cultivation of hybridoma cells in an inclined bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 176-186 
    Details
    ISSN: 0006-3592
    Keywords: animal cell ; hybridoma cell ; shear ; cell damage ; bioreactor design ; inclination ; bubble column ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Murine hybridoma cells were grown in a bubble column that was inclined up to 45° from vertical. Inclining the column by a few degrees separated the rising bubbles against the upper surface, leaving the bulk of the liquid bubble free. The liquid was circulated well by the rising bubbles, but collection of cells by rising bubbles and exposure of cells to bursting bubbles were minimized. Maximum viable cell count and exponential growth of the cells were not affected by inclination, but an inclination of 30° gave an antibody titer of 42 mg/L, which more than doubled the yield of 17 mg/L in the vertical position. By comparison, the culture gave yields of 30 mg/L when grown in spinner flasks. The enhanced antibody production in the inclined bioreactor corresponded to a prolonged stationary phase of 45 h. © 1995 John Wiley & Sons, Inc.
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    Surfactant-Modified lipase for the catalysis of the interesterification of triglycerides and fatty acids (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 187-195 
    Details
    ISSN: 0006-3592
    Keywords: interesterification reaction ; surfactant-modified lipase ; modified lipase Saiken ; triglycerides ; fatty acids ; biocatalyst ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The lipase-catalyzed intresterification of triglycerides and fatty acids in n-hexane was studied. Initially, lipase Saiken was modified with a surfactant of sorbitan esters so that its dispersibility in hydrophobic organic media was improved. The surfactant-modified lipase formed in the modification process carried out in a buffer solution has 1,3-positional specificity and predominantly catalyzed the interesterification reaction in a microaqueous n-hexane system. The modification technique converted inactive lipases to very active biocatalysts for the interesterification of triglycerides and fatty acids. The pH and the weight ratio of surfactant to enzyme used during the lipase modification process have shown significant effects in determining the recoveries of the protein and enzyme activity from the buffer solution, the protein content of the modified lipase complex after being freeze dried, and the interesterification activity of the complex. The water content in the reaction solution has strongly influenced the enzyme activity as well as the distribution of the products. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260450302
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    Effects of calcium on development of anaerobic acidogenic biofilms (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 212-218 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; calcium ; anaerobic digestion ; acidogenesis ; lactose ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anerobic biofilms with dominantly acidogenic bacteria were grown in fixed-bed recycle reactors. The influence of calcium concentration in the culture medium on biofilm mass accumulation, immobilized calcium concentration, and biofilm-specific activity was investigated. The results indicate that the biofilm mass accumulation was increased by the presence of calcium in the growth medium when calcium concentration was not higher than 120mg/L. Calcium accumulated in the biofilms increased in proportion to the calcium level in the feed. The biofilms for an increased input calcium concentration showed a trend of decrease in specific activity. The biofilms with a thickeness of less than 0.5 mm had the highest specific activity. The optimum calcium concentration for substrate consumption by the biofilms was 100 to 120 mg/L. The biofilms transferred from higher calcium medium to lower calcium medium were more susceptible to sloughing from their support surfaces, which indicates calcium's role in the stability of the biofilm structure. © 1995 John Wiley & Sons, Inc.
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    Purification of monoclonal antibodies from whole hybridoma fermentation broth by fluidized bed adsorption (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 205-211 
    Details
    ISSN: 0006-3592
    Keywords: monoclonal antibodies ; fermentation ; fluidized bed adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To achive the coarse purification of a monoclonal antibody from whole hybridoma fermentation broth a fluidized bed cation exchange process was used. The procedure consisted of application of the crude sample and washing of the bed in a fluidized mode and elution in a fixed bed mode. A completely clarified eluate was obtained with purification factors between 4 and 8 and a concentration of the desired product (monoclonal antibody) by a factor of more than 3 was achived. Thus, a combination of the three early steps of the downstream process clarification, concentration and coarse purification was possible. Two different materials were tested: a commercially available agarose-based matrix (Stream-line-SP), and a self-derivatized material based on controlled-pore glass (Bioran). Initial experiments were performed to describe the fluidization of the glass material. Comparison with the agarose material showed several differences, the agarose matrix allowing liquid flow closer to plug flow than the glass material. Increased backmixing in the liquid phase was detected when fluidizing the glass adsorbent compared with the agarose-based matrix. Despite this fact, comparison of the two materials with respect to antibody binding and elution demonstrated a similar performance. © 1995 John Wiley & Sons, Inc.
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    Characterization of tryptic casein phosphopeptides prepared under industrially relevant conditions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 196-204 
    Details
    ISSN: 0006-3592
    Keywords: tryptic casein phosphopeptides ; peptides ; casein phosphopeptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anticariogenic casein phosphopeptides (ACPP) contain the cluster sequence -Ser(P)-Ser(P)-Ser(P)-Glu-Glu- and have commercial potential as toothpaste, mouthwash, and food additives for the prevention of dental caries. In an approach to develop a commercial-scale process for the production of ACPP we have comprehensively characterized casein phosphopeptides (CPP) produced under industrially relevant conditions. Sodium caseinate (10% w/v) was hydrolyzed by Novo trypsin (commercial grade) at 50°C for 2 h and CPP were purified from the acid clarified hydrolysate by a single-step selective precipitation procedure involving Ca2+ (20 mol/mol casein) and ethanol (50% v/v) at pH 4.6 or 8.0. The individual peptides of the CPP preparations were purified by reversed-phase high-performance liquid chromatography (HPLC) and then identified by amino acid composition and sequence analyses. The yield of the pH 8.0 precipitate (13.85 ± 0.48 wt % of the caseinate) was slightly higher than that of the pH 4.6 precipitate (11.04 ± 0.30 wt % of the caseinate). However, the pH 4.6 precipitate contained predominantly (86.4 mol %) ACPP cluster peptides with small amounts of the diphosphorylated peptides (13.6 mol %), αs1(43-58) and αs2(126-136). In the pH 8.0 precipitate the cluster peptides represented a smaller proportion of the total peptides (61.9 mol %) due to increased recoveries of the diphosphorylated peptides (24.4 mol %) as well as the additional recovery of the monophosphorylated peptide β(33-48) (13.7 mol %) indicating increased cross-linking by Ca2+ at the higher pH. The recovery of the ACPP from the original caseinate was similar for both the pH 4.6 and 8.0 precipitates. Slight chymotryptic activity was detected in the industrial-grade enzyme, resulting in minor truncation of some peptides. Also some deamidation and methionine oxidation of one peptide, αs1(59-79), were detected. In conclusion, ACPP can be produced under industrially relevant conditions with only minor modifications such as slight truncation, deamidation, and methionine oxidation. However, in order to prepare casein phosphopeptides predominantly containing the cluster sequence -Ser(P)-Ser(P)-Ser(P)-Glu-Glu-, the single-step selective precipitation with Ca2+/ethanol should be performed at pH 4.6 rather than pH 8.0. © 1995 John Wiley & Sons, Inc.
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    High cell density fermentation of recombinant Vibrio cholerae for the production of B subunit of Escherichia coli enterotoxin (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 245-250 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli enterotoxin ; fed batch ; high cell density ; fermentation ; purification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High cell density fermentation studies were performed to produce the B subunit of Escherichia coli heat-labile enterotoxin (LTB) from a Vibrio cholerae culture that carries a recombinant plasmid with an ampicillin resistance gene, tac promoter, and the gene encoding LTB. Upon induction with isopropyl-β-D-thiogalactopyranoside (IPTG) the culture secreted the protein into the extracellular milieu. Fed-batch fermentation with stepwise addition of a total of 5 mM of IPTG during the active growth phase of the organism resulted in the production of 400 mg/L of LTB in 9 h and a cell optical density (OD) of 24. The LTB was purified to homogeneity with 70% recovery from the fermentation broth and was found to be chemically and biologically identical to the native protein by N-terminal amino acid sequencing and receptor binding assay. © 1995 John Wiley & Sons, Inc.
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    Effect of surfactant and particle size reduction on hydrolysis of deinking sludge and nonrecyclable newsprint (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 239-244 
    Details
    ISSN: 0006-3592
    Keywords: cellulase ; newsprint ; deinking sludge ; surfactant ; hydrolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Disposal of sludge from deinking mills represents a significant proportion of operating costs. Bioconversion of the cellulosic fraction of deinking sludge (DIS) to ethanol greatly reduces disposal costs while producing an environmentally friendly fuel. In this study, the cellulosic fraction of newsprint and deinking sludge was hydrolysed to produce fermentable sugars. For newsprint, a particle size of 1 to 1.5 mm provided optimal reaction rates in batch reactors over practical hydrolysis times, and reducing sugar concentrations as high as 35 g/L could be achieved using a fed-batch reactor configuration. For both newsprint and DIS, the hydrolysis rate increased nonlinearly with enzyme loading. Tween-80 only marginally improved sugar production but was able to release sugars from cellulosic substrates in the absence of lytic enzymes, in an amount proportional to the surfactant concentration and the substrate particle size. DIS was relatively recalcitrant to enzymatic hydrolysis, possibly due in part to inhibition by hydrophobic constituents. © 1995 John Wiley & Sons, Inc.
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    Modeling of anaerobic formate kinetics in mixed biofilm culture using dynamic membrane mass spectrometric measurement (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 219-228 
    Details
    ISSN: 0006-3592
    Keywords: formate conversion ; mass spectrometer ; anaerobic conversion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamics of the anaerobic conversion of formate in a microbial mixed culture taken from an anaerobic fluidized bed reactor was studied using a new stirred micro reactor equipped with a membrane mass spectrometer. The microreactor with a toroidally shaped bottom and pitched blade turbine and a cylindrical flow guide was thermostated and additionally equipped with a pH electrode and pH control. During fed-batch experiments using formate, the dissolved gases (methane, hydrogen, and carbon dioxide), as well as the acid consumption rates for pH control were monitored continuously. Initially and at the end of each experiment, organic acids were analyzed using ion chromatography (IC). It was found that about 50% of the formate was converted to methane via hydrogen and carbon dioxide, 40% gave methane either directly or via acetate. This was calculated from experiments using H13CO3- pulses and measurement of 12CH4 and 13CH4 production rates. About 10% of the formate was converted to lactate, acetate, and propionate, thereby increasing the measured CO2/CH4 production ratio. The nondissociated formic acid was shown to be rate determining. From the relatively high Ks value of 2.5 mmol m-3, it was concluded that formate cannot play an important role in electron transfer. During dynamic feeding of formate, hydrogen concentration always increased to a maximum before decreasing again. This peak was found to be very discriminative during modeling. From the various models set up, only those with two-stage degradation and double Monod kinetics, both for CO2 and hydrogen, were able to describe the experimental data adequately. Additional discrimination was possible with the IC measurement of organic acids. © 1995 John Wiley & Sons, Inc.
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    Batch cultivation of Methylosinus trichosporium OB3B: IV. Production of hydrogen-driven soluble or particulate methane monooxygenase activity (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 229-238 
    Details
    ISSN: 0006-3592
    Keywords: methanotroph ; methane monooxygenase ; nitrogenase ; hydrogenase ; batch culture conditions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch culture conditions were established for the formation of H2-driven whole-cell soluble or particulate methane monooxygenase (sMMO or pMMO) activity in the obligate methanotroph, Methylosinus trichosporum Ob3b, to expand its potential uses in groundwater bioremediation and the production of specific chemicals. Addition of either Ni and H2 to a nitrate-containing minimal salts growth medium or Ni and Mo to a nitrate-lacking growth medium (induces a nitrogenase that generates intracellular H2) markedly enhanced both the hydrogenase and the accompanying washed-cell H2-driven MMO activities of shake-flask cultured cells. For sMMO containing cells, H2 provided in vitro reducing power for the oxidation of chlorinated solvents such as chloroform and trichloroethylene. Cell cultivations under N2-fixing conditions in a 5-L bioreactor, however, required an initial nitrate concentration of at least 1 to 2 mM to achieve high biomass yields (5 to 7 g of dry cell wt/L) for cells producing H2-driven sMMO or pMMO activity. Elevation of the initial medium nitrate concentration to 20 mM shortened the culture time for pMMO producing cells by 40%, yet still generated an equivalent growth yield. High nitrate also shortened the culture time for sMMO containing cells by ∼25%, but it lowered their biomass yield by 26%. Upon storage for 5 weeks at room temperature, washed resting-state cells retained 90% and 70% of their H2-driven sMMO and pMMO activity, respectively. This makes their practical use quite feasible. © 1995 John Wiley & Sons, Inc.
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    Photolithotrophic cultivation of Laminaria saccharina gametophyte cells in a stirred-tank bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 251-260 
    Details
    ISSN: 0006-3592
    Keywords: macroalgal cells ; stirred-tank bioreactor ; photolithotrophic cultivation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Filamentous cell cultures derived from female gametophytes of the temperate brown macroalga Laminaria saccharina were photolithotrophically cultivated in artificial seawater medium within an illuminated 1.3-L stirred-tank bioreactor at 13°C using CO2 in air as the carbon source. A Monod model adequately described light-saturated growth. The apparent half-saturation constant (Ko) was 23 μE/m2-s, and maximum specific growth rate was 0.15 day-1. At a constant inoculation cell density of 50 mg DCW/L, biomass productivity after 26 days of cultivation increased from 630 mg DCW/L at 18 μE/m2-s to 890 mg DCW/L at 228 μE/m2-s. At 98 μE/m2-s, 1.1 vvm aeration rate, and 250 rpm impeller speed, the CO2 transfer rates (CO2 TRs) and CO2 consumption rates (rco2) were determined over the cultivation period. At peak CO2 demand, the maximum CO2 TR was 0.19 mmol CO2/L-h, but rco2 was only 0.15 mmol CO2/L-h, implying that the culture was not CO2 transport limited. This is the first reported bioreactor cultivation study of cell cultures derived from a macrophytic marine alga. © 1995 John Wiley & Sons, Inc.
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    Enzyme catalyzed biotransformations in aqueous two-phase systems with precipitated substrate and/or productTo Professor Joachim Klein on the occasion of his 60th birthday. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 261-267 
    Details
    ISSN: 0006-3592
    Keywords: Biotransformations in aqueous suspensions ; chymotrypsin ; penicillin amidase ; immobilized enzyme ; peptide synthesis ; D-phenylglycine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biotransformations catalyzed by free and immobilized enzymes have been carried out in aqueous suspensions with up to 25% (w/w) precipitated substrate or product. For the kinetically controlled synthesis of N-Acetyl-Tyr-Arg-NH2 with up to 0.8 M insoluble activated substrate N-Acetyl-TyrOEt catalyzed by α-chymotrypsin (EC3.4.21.1) the dipeptide yield was found to be 〉90%. This and the space-time yields were higher than those observed for one-phase aqueous systems and much higher than in systems where the insoluble substrate had been solubilized by addition of organic solvents. In the equilibrium controlled hydrolysis of 0.4 M D-phenylglycine-amide catalyzed by immobilized penicillin amidase (EC 3.5.1.11) the product precipitates. The enzyme immobilized in the support with the smallest pores could be reused without reduction in the rate due to precipitation in the pores. This decreases the number of immobilized enzyme molecules that can be used as biocatalysts. The latter was observed for supports with larger pores as the solubility decreases with increasing particle size. These results demonstrate that biotransformations with insoluble substrates or products using free or immobilized enzymes can be easily carried out in aqueous two-phase systems, without organic solvents, provided that the pore sizes of the supports are sufficiently small and that the rate of mass transfer from the precipitated substrate is large. The latter increases with decreasing particle size. © 1995 John Wiley & Sons, Inc.
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    Enzymic peptide synthesis in microaqueous, solvent-free systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 276-278 
    Details
    ISSN: 0006-3592
    Keywords: enzymic peptide synthesis ; solvent free system, chymotrypsin ; thermolysin ; peptides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermolysin-catalyzed (EC 3.4.24.4) and chymotrypsin-catalyzed (EC 3.4.21.1) peptide synthesis reactions were accomplished without any organic solvent in the presence of low amounts of water under sonication and fluidization. The systems used are considered to be microaqueous solvent-free ones. The influence of several reaction parameters, such as time, the amount of enzyme, the amount of water in free form or bound as hydration water, and the N/C component ratio, on the vield of the thermolysin-catalyzed synthesis of Z-Phe-Leu-NH2 (up to 87% yield) was investigated in a sonicated system. Besides Z-Phe-Leu-NH2, the tripeptide derivatives Ac-Xaa-Trp-Leu-NH2, (Xaa = Gly, Ala) were also obtained in good yields of 79 and 71% respectively. In the latter case, no hydrolytic side reactions were observed. Using a fluidized-bed reactor, chymotrypsin- and thermolysin-catalyzed syntheses of N-protected di- and tripeptide amides could be perfromed with yields in the range of 10 to 40%. © 1995 John Wiley & Sons, Inc.
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    Production of poly(D-3-hydroxybutyrate) from CO2, H2, and O2 by high cell density autotrophic cultivation of Alcaligenes eutrophus (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 268-275 
    Details
    ISSN: 0006-3592
    Keywords: poly(D-3-hydroxybutyrate) ; P(3HB) ; Alcaligenes eutrophus ; gas explosion ; autotroph ; hydrogen oxidizing bacterium ; carbon dioxide fixation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrogen-oxidizing bacterium, Alcaligenes eutrophus autotrophically produces biodegradable plastic material, poly(D-3-hydroxybutyrate), P(3HB), from carbon dioxide, hydrogen, and oxygen. In autotrophic cultivation of the microorganism, it is essential to eliminate possible occurrence of gas explosions from the fermentation process. We developed a bench-plant scale, recycled-gas, closed-circuit culture system equipped with several safety features to perform autotrophic cultivation of A. eutrophus by maintaining the oxygen concentration in the substrate gas phase below the lower limit for a gas explosion (6.9%). The culture vessel utilized a baskettype agitator, resulting in a KL a value of 2970 h-1. Oxygen gas was also directly fed to the fermentor separately from the other gases. As a result, 91.3 g · dm-3 of the cells and 61.9 g · dm-3 of P(3HB) were obtained after 40 h of cultivation under this oxygen-limited condition. The results compared favorably with those reported for mass production of P(3HB) by heterotrophic fermentation. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    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.260450401
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    Kinetics of nitrate inhibition of carbon tetrachloride transformation by a denitrifying consortia (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 279-284 
    Details
    ISSN: 0006-3592
    Keywords: carbon tetrachloride ; nitrate inhibition ; biodegradation ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of nitrate inhibition of carbon tetrachloride (CT) transformation were examined using a denitrifying consortium. Comparison of data from fed-batch experiments to the model reported by Hooker et al. indicate that the inhibition constant ranges between 3.2 and 21 mg/L, with an average of 8.8 mg/L. This range is much lower than the previously reported value of 169 mg/L. Simulations using the corrected parameter accurately reflect this new data and the data reported by Hooker et al. In contrast, the earlier reported coefficient value does not reflect the data reported in this work. © 1995 John Wiley & Sons, Inc.
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    Microbial production of (+)-trans-isochorismic acid (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 285-291 
    Details
    ISSN: 0006-3592
    Keywords: Klebsiella pneumoniae 62-1 ; isochorismate hydroxymutase (E.C. 5.4.99.6) ; affinity immobilization ; isochorismate excretion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two methods are described for the preparation of enantiomerically pure (+)-trans-isochorismic acid, an important metabolite of the postchorismate pathway. Both methods can be employed to prepare isotopically labeled isochorismic acid. One of the two methods is suitable to prepare bulk quantities of isochorismic acid using a recombinant strain of Klebsiella pneumoniae 62-1. © 1995 John Wiley & Sons, Inc.
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    Intracellular flux analysis in hybridomas using mass balances and in vitro 13C nmr (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 292-303 
    Details
    ISSN: 0006-3592
    Keywords: fluxes ; intracellular fluxes ; hybridoma cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Intracellular fluxes are important in defining cellular physiology and its changes in response to environmental variations. Stoichiometric balances combined with extra cellular metabolite measurements were applied to the estimation of intracellular fluxes and the study of energy metabolism in the hybridoma cell line ATCC CRL 1606. Redundant measurements allowed the evaluation of the consistency of the stoichiometry, measurements, and pseudo-steady-state assumption leading to refinement of the assumed biochemistry and identification of measurement errors. To validate the flux estimates, two batch experiments were performed with glucose labeled in the 1 position with 13C. The distribution of 13C in secreted lactate was measured via nuclear magnetic resonance spectroscopy (NMR) and compared to that predicted from the estimated intracellular fluxes. There was good agreement between the measured and estimated isotope distributions, demonstrating the validity of the flux estimates obtained from stoichiometric balances. © 1995 John Wiley & Sons, Inc.
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    Removal of phenols and aromatic amines from wastewater by a combination treatment with tyrosinase and a coagulant (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 304-309 
    Details
    ISSN: 0006-3592
    Keywords: phenol ; substituted phenol ; tyrosinase ; immobilization ; chitosan ; coagulant ; immobilized enzyme ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Removal of phenols and aromatic amines from industrial wastewater by tyrosinase was investigated. A color change from colorless to darkbrown was observed, but no precipitate was formed. Colored products were found to be easily removed by a combination treatment with tyrosinase and a cationic polymer coagulant containing amino group, such as hexamethylenediamine-epichlorohidrin polycondensate, polyethleneimine, or chitosan. The first two coagulants, synthetic polymers, were more effective than chitosan, a polymer produced in crustacean shells. Phenols and aromatic amines are not precipitated by any kind of coagulants, but their enzymatic reaction products are easily precipitated by a cationic polymer coagulant. These results indicate that the combination of tyrosinase and a cationic polymer coagulant is effective in removing carcinogenic phenols and aromatic amines from an aqueous solution. Immobilization of tyrosinase on magnetite gave a good retention of activity (80%) and storage stability i.e., only 5% loss after 15 days of storage at ambient temperature. In the treatment of immobilized tyrosinase, colored enzymatic reaction products were removed by less coagulant compared with soluble tyrosinase. © 1995 John Wiley & Sons, Inc.
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    Development of optimized transfectoma cell lines for production of chimeric antibodies in hollow fiber cell culture systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 310-319 
    Details
    ISSN: 0006-3592
    Keywords: chimeric antibodies ; transfectoma cells ; hollow fiber fermentor ; immunoglobulin enhancer ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Methods for the selection of transfectoma cells that express large quantities of mouse-human chimeric antibodies have been develped. SP2/0 mouse myeloma cells were transfected with pSV2-gpt and pSV2-neo based immunoglobulin expression vectors. Double transfectants were selected using the xanthine-guanine phosphoribosyl transferase (gpt)and the neomycin (neo) selection marker genes. ELISA-based screening of transfectoma clones resulted in the isolation of IgG-producing transfectomas. Introduction of the kappa light-chain 3′-enhancer into the light-chain expression vector significantly increased immunoglobulin expression, but only when the enhancer was located at its physiological site, 9 kb downstream of the kappa constant region exon. With some of the transfectomas, final yields of up to 80 mg/L of chimeric IgG were obtained in conventional flask cultures using serum-free growth medium. A pilot-scale AcuSyst Maximizer hollow fiber cell culture system was used for the production of gram amounts of chimeric IgG. Results obtained with different transfectoma clones in conventional culture were not fully predictive for yields in the hollow fiber system. In contrast, differences in productivity between individual clones in the laboratory-scale Tecnomouse cell culture unit were comparable with those in the Maximizer system. Up to 200 mg of chimeric IgG were produced per day in one Maximizer bioreactor. © 1995 John Wiley & Sons, Inc.
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    Evaluation of cellulase recycling strategies for the hydrolysis of lignocellulosic substrates (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 328-336 
    Details
    ISSN: 0006-3592
    Keywords: cellulase recycling ; lignin ; lignocellulose hydrolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recycling of cellulases should lower the overall cost of lignocellulosiic bioconversion processes. In this study, three recycling strategies were evaluated to determine their efficiencies over five successive rounds of hydrolysis. The effect of lignin on recycling was examined by comparing water-washed, steam-exploded birch (WB; 32% lignin) and WB which had been further extracted with alkali and peroxide (PB; 4% lignin). When the cellulases were recovered from the residual substrates after partial hydrolysis of both substrates, the recovered cellulase activity toward the mixture of fresh and residual substrates decreased after each recycling step. When the cellulases in the supernatants were also recycled, up to 20% more activity could be recovered. In both of these cases, the recovered activities did not correspond to the activities expected from the amount of cellulase protein recovered during recycling. The best recovery was obtained when the cellulases were recovered from both the residue and the supernatant after complete hydrolysis of the PB substrate. In this case, all of the originally added cellulase activity could be recovered for four consecutive hydrolysis rounds. However, when the same recycling strategy was carried out using the WB substrate, the recovered cellulase activity declined quickly with each recycling round. In all three of the recycling strategies, lower cellulase activities were recovered from the substrates with higher lignin contents. © 1995 John Wiley & Sons, Inc.
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    Dielectrophoretic separation of cells: Continuous separation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 337-343 
    Details
    ISSN: 0006-3592
    Keywords: dielectrophoresis ; cells, separation of ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dielectrophoresis is the movement of particles in non-uniform alternating and direct current (AC, DC) electric fields. When nonuniform electric fields are created between microelectrodes, cells will redistribute themselves around the electrodes, the force holding the cells in place dependig on the local electric field and on the electrical properties of the cells themselves and the suspending medium. Steric drag forces produced by a gentle fluid flow in the chamber can be used to separate cells by selectively lifting cells from potential energy wells produced by the electric field. The technique is demonstrated in the batch separation of bacteria, yeast cells, and plant cells. Continuous separation and extraction of two cell types can be achieved by repeated reversing of the fluid flow direction in phase with the switching on and off of the applied voltage, and the efficacy of the technique is demonstrated for viable and nonviable (heat-treated) yeast cells. © 1995 John Wiley & Sons, Inc.
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    Operational patterns affecting lactic acid production in ultrafiltration cell recycle bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 320-327 
    Details
    ISSN: 0006-3592
    Keywords: cell recycle reactor ; ultrafiltration tubular membranes ; high lactic acid productivities ; best operational conditions ; different dilution rates ; start-up strategy ; membrane permeability ; long-term fermentations ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lactic acid production with cell recycling on an ultrafiltration tubular membrane reactor was studied; higher lactic acid concentrations as well as productivities were obtained under long-term fermentations compared with other high cell density systems. Different operational conditions, namely dilution rates and start-up modes, were assessed. Performances were very different at the three different dilution rates tested (D = 0.20 h-1, D = 0.40 h-1, or D = 0.58 h-1). The different behaviours are discussed and factors responsible for them are presented. The best way to operate for lactic acid production is chosen, the dilution rate of D = 0.40 h-1 being the one providing the best overall performance. On the other hand, results show that of the two start-up modes tested, continuous start (membrane open) permits higher permeabilities throughout the operational runs than batch start (membrane closed). Operational stability was found to be directly associated with membranes that work at “steady state,” the membrane permeability being kept around 15 L/m2 h. Optimized cell bleed can improve time of operation if such membrane permeability can be maintained for a longer time. A comparison of results with those obtained in other lactic acid production systems is presented; such comparison shows that this tubular ultrafiltration membrane cell recycle reactor presents three important advantages: (1) concomitant lactic acid concentrations and productivities; (2) long periods of operation at reasonable permeabilities; and (3) good mechanical stability permitting the use of steam sterilization. © 1995 John Wiley & Sons, Inc.
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    Esterification reactions catalyzed by Chromobacterium viscosum lipase in CTAB-based microemulsion systems (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 344-355 
    Details
    ISSN: 0006-3592
    Keywords: esterification ; Chromobacterium viscosum ; lipase ; microemulsions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chromobacterium viscosum (CV) lipase solubilized in water-in-oil (w/o) microemulsions based on the cationic surfactant hexadecyltrimethylammonium bromide (CTAB) have been used for multigram-scale ester synthesis, including the kinetic resolution of a secondary alcohol. The stability of CV lipase in all the CTAB microemulsions studied was excellent and was superior to that observed in aqueous buffer at the same pH and temperature. Kinetic studies were performed using the synthesis of ethylhexadecanoate as a model reaction. Under pseudo-first-order conditions, the synthesis rates were linearlydependent on the enzyme and fatty acid concentrations and the R dependence shows the characteristic bell-shaped curve (where R = [H2O]/[surfactant]). The dependence of enzyme activity toward octyldecanoate synthesis on the pH of the dispersed buffer phase is in marked contrast to that observed for the pH dependence of CV lipase toward p-nitrophenylbutyrate hydrolysis. In the former case, the pH-activity profile is approximately sigmoidal, which may reflect the ionization state of the fatty acid substrate. In the latter case, the pH dependence is minimal at both R = 10 and R = 50, suggesting the enzyme does not experience a changed pH environment. Inclusion of a pH-sensitive probe molecule into those incubations containing fatty acid clearly demonstrates that the probe molecule experiences a changed environment consistent with that expected for the selected buffer. An in situ Fourier transform nuclear magnetic resonance (FT-NMR) assay has been developed which allows continuous monitoring of the esterification reactions, thereby providing an additional means of determining initial rates. The method may be of general value for lipase assays in microemulsions since it may provide, at the same time, information regarding enzyme regioselectivity. © 1995 John Wiley & Sons, Inc.
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    Kinetics of ethanol production by recombinant Escherichia coli KO11 (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 356-365 
    Details
    ISSN: 0006-3592
    Keywords: Escherichia coli KO11 ; ethanol production ; kinetic model ; lignocellulosic hydrolysate ; fermentation, mixed sugar ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fermentation kinetics for separate as well as simultaneous glucose and xylose fermentation with recombinant ethanologenic Escherichia coli KO11 are presented. Glucose and xylose were consumed simultaneously and exhibited mutual inhibition. The glucose exhibited 15 times stronger inhibition in xyclose fermentation than vice versa. The fermentation of condensate from steampretreated willow (Salix) was investigated. The kinetics were studied in detoxified as well as in nondetoxified condensate. The fermentation of the condensate followed two phases: First the glucose and some of the pentoses (xylose in addition to small amounts of arabinose) were fermented simultaneously, and then the remaining part of the pentoses were fermented. The rate of the first phase was independent of the detoxification method used, whereas the rate of the second phase was found to be strongly dependent. When the condensate was detoxified with overliming in combination with sulfite, which was the best detoxification method investigated, the sugars in the condensate, 9 g/L, were fermented in 11 h. The same fermentation took 150 h in nondetoxified condensate. The experimental data were used to develop an empirical model, describing the batch fermentation of recombinant E. coli KO11 in the condensate. The model is based on Monod kinetics including substrate and product inhibition and the sum of the inhibition exerted by the rest of the inhibitors, lumped together. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    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.260450501
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    Development of effective modified cellulase for cellulose hydrolysis process (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 366-373 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic hydrolysis ; cellulase ; polyoxyalkylene ; adsorption ; reactive two-phase partition ; solubilization in organic solvent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cellulase was modified with amphilic copolymers made of α-allyl-ω-methoxy polyoxyalkylene (POA) and maleic acid anhydride (MAA) to improve the cellulose hydrolytic reactivity and cellulase separation. Amino groups of the cellulase molecule are covalently coupled with the MAA functional groups of the copolymer. At the maximum degree of modification (DM) of 55%, the modified cellulase activity retained more than 80% of the unmodified native cellulase activity. The modified cellulase shows greater stability against temperature, pH, and organic solvents, and demonstrated greater conversion of substrate than native cellulase does. Cellulase modification is also useful for controlling strong adsorption of cellulase onto substrate. Moreover, cellulase modified with the amphiphilic copolymer displays different separation characteristics which are new. One is a reactive two-phase partition and another is solubility in organic solvents. It appears that these characteristics of modified cellulase work very effectively in the hydrolysis of cellulose as a total system, which constitutes the purification of cellulase from culture broth, hydrolysis of cellulose, and recovery of cellulase from the reaction mixture. © 1995 John Wiley & Sons, Inc.
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    Preferential release of one daughter cell during division of immobilized chinese hamster ovary cells (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 374-378 
    Details
    ISSN: 0006-3592
    Keywords: cell culture ; patterened surfaces ; cell adhesion ; hydrogel ; polyHEMA ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chinese hamster ovary (CHO) cells were attached to tiny adhesive sites in poly-2-hydroxyethyl methacrylate(polyHEMA-) coated glass, and their divison properties were examined. The adhesive sites were produced by placing a metal mask, containing 8-μm-diameter holes arranged in a regular pattern, on top of the coated glass and exposing the sandwich to glow discharge treatment. This treatment produced an ordered array of circular cavities in the polyHEMA down to the glass. These adhesive sites were smaller in diameter than a newborn CHO cell, so that, upon division, there would theoretically be room for only one of the two new daughter cells to remain attached. It was found that individual CHO cells attached to, and grew upon, the sites, and that division normally resulted in the releas of one of the two new daughters. It is concluded that this culture technique has applications in research on the mammalian cell cycle, cell partitioning, and cellular senescence. © 1995 John Wiley & Sons, Inc.
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    Working at controlled water activity in a continuous process: The gas/solid system as a solution (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 387-397 
    Details
    ISSN: 0006-3592
    Keywords: transesterification ; water activity ; lipolytic enzymes ; gas ; bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fusarium solani cutinase and Candida cylindracea lipase were used to catalyze a transesterification reaction in a continuous gas/solid bioreactor. In this system, a solid phase composed of a packed enzymatic preparation was continuously percolated with carrier gas which fed substrate and removed reaction products simultaneously. Different conditions of immobilization were used and compared to the results obtained with a nonsupported enzyme. The enzymatic activity was found to be highly dependent of a key parameter: water activity (aw). Biocatalyst stability was greatly influenced by water activity and the choice of immobilization technique for the enzymatic material. For free and adsorbed enzymes, water requirements exhibited optima which corresponded to the complete hydration coverage of the protein. These optima presented a good correlation with the isotherm sorption curves obtained for the different preparations. In this work are reported the results concerning the possibility of using a continuous system able to operate at controlled water activity in a heterogeneous medium. Lipolytic enzyme in such a system appears to be a new process for the biotransformation of volatile esters. © 1995 John Wiley & Sons, Inc.
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    Performances of a full-scale novel multiplate anaerobic reactor treating cheese whey effluent (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 398-405 
    Details
    ISSN: 0006-3592
    Keywords: anaerobic digestion ; full-scale ; granule activity ; multiplate reactor ; solid retention ; whey permeate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A 450-m3 multiplate anaerobic reactor (MPAR) has been started-up in April 1992 for treating wastewater (whey permeate and domestic wastewater) at the Nutrinor (Lactel) cheese factory in Chambord (Québec, Canada). The MPAR consists of four superimposed sections. The liquid flows upwards from one section to the next, while the gas is collected below each plate and evacuated through side-outlets. The wastewater is concurrently distributed at the bottom of the first, second, and third sections, as 50%, 33%, and 17% of the total influent stream, respectively. Granular anaerobic sludge at an initial concentration of 30 kg of volatile suspended solids (VSS) per cubic meter of reactor liquid volume was used to inoculate the reactor. Under normal operation of the factory, the chemical oxygen demand (COD) concentration of the influent ranged from 20 to 37 kg COD m-3. The reactor organic loading rate (OLR) fluctuated between 9 and 14.7 kg COD m-3 d-1 for hydraulic retention times (HRT) maintained between 55 and 68 h. At the highest OLR, the MPAR showed an efficiency of 98% and 92% for soluble and total COD removal, respectively, and a methane production rate averaging around 4 m3 m-3 d-1.Biomass-specific activities ranged between 7 and 51, 1.3 and 8.5, 5.3 and 12.2, 60 and 119, and 119 and 211 mmol g-1 VSS d-1 for glucose, propionate, acetate, formate, and hydrogen, respectively. Average equivalent-diameter of the granules was around 0.65 mm. The MPAR reactor generally showed a large capacity for solid retention with a biomass content between 32 and 37 kg VSS m-3. © 1995 John Wiley & Sons, Inc.
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    A novel recycle batch immobilized cell bioreactor for propionate production from whey lactose (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 379-386 
    Details
    ISSN: 0006-3592
    Keywords: propionic acid fermentation ; Propionibacterium acidipropionici ; immobilized cell bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recycle batch fermentations using immobilized cells of Propionibacterium acidipropionici were studied for propionate production from whey permeate, de-lactose whey permeate, and acid whey. Cells were immobilized in a spirally wound fibrous sheet packed in a 0.5-L column reactor, which was connected to a 5-L stirred tank batch fermentor with recirculation. The immobilized cells bioreactor served as a breeder for these recycle batch fermentations. High fermentation rates and conversions were obtained with these whey media without nutrient supplementation. It took ∼55 h to ferment whey permeate containing ∼45 g/L lactose to ∼20 g/L propionic acid. Higher propionate concentrations can be produced with various concentrated whey media containing more lactose. The highest propionic acid concentration obtained with the recycle batch reactor was 65 g/L, which is much higher than the normal maximum concentration of 35 to 45 g/L reported in the literature. The volumetric productivity ranged from 0.22 g/L · h to 0.47 g/L · h, depending on the propionate concentration and whey medium used. The corresponding specific cell productivity was 0.033 to 0.07 g/L · g cell. The productivity increased to 0.68 g/L · h when whey permeate was supplemented with 1% (w/v) yeast extract. Compared with conventional batch fermentation, the recycle batch fermentation with the immobilized cell bioreactor allows faster fermentation, produces a higher concentration of product, and can be run continually without significant downtime. The process also produced similar fermentation results with nonsterile whey media. © 1995 John Wiley & Sons, Inc.
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    Fluid shear effects on suspension cultures of Morinda citrifolia (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 415-425 
    Details
    ISSN: 0006-3592
    Keywords: plant cell suspension culture ; capillary shear loop ; Morinda citrifolia ; shear susceptibility ; morphology ; stirred tank reactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The shear susceptibility of cell suspension cultures of the plant cell Morinda citrifolia was investigated by subjecting the cells to the well-defined shear field generated in turbulent flow through a capillary. Suspensions were circulated using a peristaltic pump and average shear stresses between 25 and 350 N m-2 were generated in the capillary test section. Control experiments were performed to assess the possible contribution of the peristaltic pump to the observed cell damage. There was clear evidence of pump-induced damage at the more severe test conditions and all viability measurements were corrected accordingly. Both shake flask suspension cultures (aged between 9 and 15 days) and repeated batch fermentation cultures, grown in a stirred tank reactor (STR) under a variety of controlled agitation conditions, were tested in the capillary shear loop. The cell damage incurred was evaluated in terms of suspension viability, as determined by a dye exclusion technique. Viability loss was found to conform closely to a first-order model in which the rate constant was observed to increase with the imposed shear stress. Furthermore, a linear relationship was identified between the specific death constant and the cumulative energy dissipated. Post-shear morphological measurements showed that the chain length distribution is shifted toward markedly lower values. In comparison with shake flask cultures, repeated batch fermentation cultures exhibited a marked increase in sensitivity to capillary shear. Based upon the determined morphological characteristics, this result is primarily attributable to the increased chain lengths characteristic of the repeated batch cultures. © 1995 John Wiley & Sons, Inc.
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    Effects of sorbitol addition on the action of free and immobilized hydrolytic enzymes in organic media (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 406-414 
    Details
    ISSN: 0006-3592
    Keywords: chymotrypsin ; differential scanning calorimetry ; ligands ; lipase ; organic media ; sorbitol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of the addition of sorbitol on the activity and stability of enzymes was examined by monitoring transesterification reactions performed in organic media at various water activities (aw = 0.08 to 0.97). Lipases from Chromobacterium viscosum and Candida rugosa immobilized on celite, and chymotrypsin, free or immobilized on celite, were used. When the sorbitol-containing enzymes were employed, higher reaction rates and less hydrolysis were observed. Immobilization of chymotrypsin resulted in high activity and operational stability, while the nonimmobilized enzyme was stable only in the presence of sorbitol. The activity of all preparations diminished after washing them with pyridine to remove sorbitol. Furthermore, severe stability problems occurred in the preparations lacking sorbitol. Sorbitol treatment, even after removal of the sorbitol itself, improved the activity of nonimmobilized chymotrypsin relative to the washed control. On the other hand, washing to remove sorbitol had a negative effect on the activity of both coimmobilized lipase and coimmobilized chymotrypsin. Addition of a substrate analogue, N-acetyl-L-phenylalanine, to chymotrypsin yielded a preparation that exhibited higher activity than both the control and its sorbitol-containing counterpart. Differential scanning calorimetry measurements revealed that the chymotrypsin-sorbitol complex was stable against thermal denaturation, undergoing transition at a high temperature (89°C). The transition temperatures of the substrate-containing chymotrypsin and of the control were identical (72°C). © 1995 John Wiley & Sons, Inc.
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    Relation between dissolved oxygen concentration and ajmalicine production rate in high-density cultures of Catharanthus roseus (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 435-439 
    Details
    ISSN: 0006-3592
    Keywords: Catharanthus roseus ; ajmalicine production rate ; dissolved oxygen concentration ; kinetic model ; high-density culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The relation between dissolved oxygen (DO) and the ajmalicine production rate of Catharanthus roseus was investigated in 15-L tank reactors at constant stirrer speed and gas flow rate. Below a DO concentration of 29% of air saturation the ajmalicine production rate was less than 0.06 μmol/g/d. Above a DO of 43% the ajmalicine production rate was constant at 0.21 μmol/g/d. Between a DO of 29% and 43% there was a strong relation between the ajmalicine production rate and the DO concentration. After a period of at least 12 days at DO ≤29% the culture lacked the ability to adapt to a DO ≥57%. A kinetic equation is proposed for the relation between DO and the specific ajmalicine production rate. © 1995 John Wiley & Sons, Inc.
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    Controlling enzyme-catalyzed regioselectivity in sugar ester synthesis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 426-434 
    Details
    ISSN: 0006-3592
    Keywords: regioselectivity of enyzmatic catalysis ; sucrose acylation in organic solvents ; molecular modeling ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rational control over enzyme-catalyzed regioselectivity has been studied using sucrose acylation by vinyl esters in organic media as a model. Subtilisins BPN' and Carlsberg preferentially acylate at the 1′-hydroxyl of sucrose with some acylation observed at the 6-hydroxyl. The preference for the 1′-hydroxyl is strongly affected by the hydrophobicity of the organic solvent and the chain length of the vinyl ester. Increasingly hydrophobic solvents and longer chain lengths lower the favorable formation of the 1′-acylation and improve 6-acylation. Molecular modeling of sucrose in the binding pocket of subtilisin BPN' shows that the 1′-acylation is favored in solvents that can solvate sugars (such as pyridine) as the glucose moiety is exposed to the medium, whereas 6-acylation leaves the entire sucrose molecule buried within the enzyme's binding pocket. Thus, 1′-acylation is sterically more favorable than 6-acylation. Increasingly hydrophobic solvents affect regioselectivity by changing the degree of solvation of the glucose moiety in the medium and forcing the sucrose 1′-ester completely into the binding pocket. In a related modeling, the vinyl ester chain length was shown to modulate regioselectivity by controlling the bond angles between the resulting acylenzymes and the sucrose thereby affecting the positioning of the sucrose in the binding pocket of subtilisin BPN'. This study shows that control over enzymic regioselectivity can be achieved by rational choices of substrate and solvent. © 1995 John Wiley & Sons, Inc.
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    Diffusion of Cu2+ in calcium alginate gel beads: Further analyses (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 454-457 
    Details
    ISSN: 0006-3592
    Keywords: copper ; diffusion ; alginate gel beads ; diffusion models ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The diffusivity of Cu2+, as determined by previous authors from analysis of experimental data in terms of the shrinking core (SCM) and linear absorption (LAM) models, is examined in light of the ability of the models to curve fit all the data. It is concluded from this further analysis that previous conclusions depicting the LAM to have an advantage over the SCM for predictive value are not justified. It is also shown that equally good curve fits can be obtained with a recent absorption/desorption model of diffusion which considers directly, through distribution theory, the effect of heterogeneity of material properties on the rate of diffusion. © 1995 John Wiley & Sons, Inc.
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    Metal recognition by in-vitro selection (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 458-462 
    Details
    ISSN: 0006-3592
    Keywords: molecular recognition ; in vitro selection ; metal-binding protein ; molecular process engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We propose an in vitro selection strategy to identify bacteriophage variants that recognize metal ions in solution. In 6 M urea, phage T7 loses 99.9% of its activity in less than 5 min. Inactivation is accelerated by gold, but slowed by zinc and magnesium. Selection of phage over five generations in the presence of gold, zinc, and magnesium increases phage half-lives 4-, 10-, and 70-fold, respectively. As selections are repeated, phage become increasingly dependent on the specific metal employed in the selection, indicating the suitability of the strategy for optimization of metal-ion recognition. © 1995 John Wiley & Sons, Inc.
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    Transformation capacities of chlorinated organics by mixed cultures enriched on methane, propane, toluene, or phenol (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 440-449 
    Details
    ISSN: 0006-3592
    Keywords: transformation capacity ; product toxicity ; oxygenase enzymes ; chlorinated organics ; trichloroethylene ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The degradation of trichloroethylene (TCE), chloroform (CF), and 1,2-dichloroethane (1,2-DCA) by four aerobic mixed cultures (methane, propane, toluene, and phenol oxidizers) grown under similar chemostat conditions was measured. Methane and propane oxidizers were capable of degrading both saturated and unsaturated chlorinated organics (TCE, CF, and 1,2-DCA). Toluene and phenol oxidizers degraded TCE but were not able to degrade CF, 1,2-DCA, or other saturated organics. None of the cultures tested were able to degrade perchloroethylene (PCE) or carbon tetrachloride (CC4). For the four cultures tested, degradation of each of the chlorinated organics resulted in cell inactivation due to product toxicity. In all cases, the toxic products were rapidly depleted, leaving no toxic residues in solution. Among the four tested cultures, the resting cells of methane oxidizers exhibited the highest transformation capacities (Tc) for TCE, CF, and 1,2-DCA. The Tc for each chlorinated organic was observed to be inversely proportional to the chlorine carbon ratio (Cl/C). The addition of low concentrations of growth substrate or some catabolic intermediates enhanced TCE transformation capacities and degradation rates, presumably due to the regeneration of reducing energy (NADH); however, addition of higher concentrations of most amendments reduced TCE transformation capacities and degradation rates. Reducing energy limitations and amendment toxicity may significantly affect Tc measurements, causing a masking of the toxicity associated with chlorinated organic degradation. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995) 
    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.260450601
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    Enhancing effect of albumin hydrolysate on ethanol production employing Saccharomyces sake (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 450-453 
    Details
    ISSN: 0006-3592
    Keywords: ethanol production ; albumin hydrolysate ; plasma membrane ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enhancing effect of albumin hydrolysate on ethanol production was investigated in ethanol fermentations using Saccharomyces sake. In batchwise ethanol production, addition of supplemental albumin hydrolysate and phosphatidylcholine, or albumin hydrolysate alone, brought about a more than 60% increase in final ethanol concentration (148 or 144 g/L compared with 88 g/L with no supplementation [control] after 72 h). The effect of the supplements is believed to be due to an enhanced alcohol tolerance of cells grown in media containing the supplements. Cells grown in media containing albumin hydrolysate were enriched in phenyalanine, tyrosine, and methionine in their plasma membranes. All three amino acids were also present in considerable amounts in the albumin hydrolysate. This fact suggests that the three amino acids, which are present in albumin hydrolysate, are incorporated into the plasma membranes of cells. Under ethanol production conditions in which only one amino acid among the components of albumin hydrolysate was excluded, namely phenlalanine, tyrosine, or methionine, significant reductions in ethanol production resulted. © 1995 John Wiley & Sons, Inc.
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    Dynamics of biofilm detachment in biofilm airlift suspension reactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 481-487 
    Details
    ISSN: 0006-3592
    Keywords: biofilms ; detachment ; substrate loading ; airlift reactor ; abrasion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamic change in the overall detachment rate of spherical biofilms in a biofilm airlift suspension reactor was measured after a downshift of the substrate loading rate to zero while all other conditions remained constant. In contrast to the expectations, the overall detachment rate decreased rapidly to a nearly stable level. Correlations available from literature were not able to describe this phenomenon. Concepts were formulated which can describe the observations from this study. Research under dynamic conditions and careful monitoring of the biofilm surface area and biofilm morphology are necessary to elucidate and discriminate biofilm detachment mechanisms. © 1995 John Wiley & Sons, Inc.
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    The protective effect of specific medium additives with respect to bubble rupture (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 473-480 
    Details
    ISSN: 0006-3592
    Keywords: cell adhesion ; protective additives ; interfacial tensions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A significant degree of cell damage is observed during suspension cell culture with air sparging. Protective agents can be added to the culture medium to protect the cells from damage. It has been observed that cells tend to adhere to air-medium interfaces and cell damage is mainly due to this cell-bubble interaction; protective additives have been found to prevent this cell adhesion to the bubble surfaces. In this article, it is demonstrated that the interfacial tension between the air and medium is related to the effectiveness of the protective additives to prevent adhesion of cells to this interface. Five different types of additives (Pluronic F-68, Methocels, dextran, Polyvinyl alcohol, and polyethylene glycols) were studied in an effort to determine their protective characteristics. Liquid-vapor interfacial tensions of the culture medium, with and without the additives, were measured by two different techniques (maximum bubble pressure method and Wilhelmy plate method). In addition, visualization techniques showed that in the presence of certain protective additives cells do not adhere to the bubble surface. Results obtained from these experiments indicate that the additives which rapidly lower the liquid-vapor interfacial tension of the culture medium also prevent adhesion of cells to the bubble surface. Experiments have also been conducted to determine the number of cells killed due to bubble rupture, and it was observed that this number is related to the amount of cells adhering to the bubble surface. © 1995 John Wiley & Sons, Inc.This article is a US Government Work and, as such, is in the public domain in the United States of America.
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    Death mechanisms of animal cells in conditions of intensive agitation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 463-472 
    Details
    ISSN: 0006-3592
    Keywords: apoptosis ; animal cell death ; hybridoma cells ; agitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The question is addressed as to whether cells which are subject to high-energy dissipation rates in agitated bioreactors show an apoptotic response. Murine hybridoma cells in batch culture were agitated in bench-scale (1-L) bioreactors without gas sparging. At an energy dissipation rate of 1.5 W m-3 there was no apparent damage. At 320 W m-3 cell viability declined, and increasing proportions of the dead cells displayed the morphological features of apoptosis, but necrosis also remained as a significant mechanism of death. When cells were subjected to the intensive energy dissipation rate of 1870 W m-3 in a bioreactor without gas headspace, the cell number dropped by 50% within 2 h and a subpopulation of smaller-sized cells emerged. This excluded trypan blue but showed some apoptotic characteristics such as reduced and condensed DNA content and low F-actin content. The incidence of apoptotic activity was further demonstrated by the appearance of numerous apoptotic bodies. Analysis of the cell cycles of both small and normal size populations indicated that greater proportions of S and G2 cells had become apoptotic and there was evidence of preferential survival of G1 cells. It is suggested that two mechanisms of cell death are apparent in hydrodynamically stressful situations, but their relative expression depends on the energy dissipation rate. © 1995 John Wiley & Sons, Inc.
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    Evaluation and applications of optical cell density probes in mammalian cell bioreactors (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 495-502 
    Details
    ISSN: 0006-3592
    Keywords: optical cell density probes ; turbidity probes ; on-line monitoring ; in situ probes ; mammalian cell bioreactors/fermentors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line optical cell density probes were implemented to continuously monitor the cell densities in mammalian cell bioreactor and to achieve advanced bioreactor controls. We tested cell density probes from six manufacturers in high cell density bioreactors. When externally calibrated, Aquasant and Ingold backscattering probes produced the most linear probe responses (PR) versus cell density (CD), followed by the ASR and Cerex laser probes. Monitek and Wedgewood transmission probes had lower resolutions. All probes were tested in two murine hybridoma fermentations. Cell densities varied between 1 × 106 cells/mL to 20 × 106 cells/mL and the bioreactors were operated for 5 to 7 weeks. For our bioreactors, Aquasant, Ingold, ASR, Wedgewood, and Monitek probes gave satisfactory responses. Little fouling was observed with any probe at the end of 2 weeks. Fouling was a possibility after 3 weeks in one bioreactor but its effect can be easily corrected. Cell density control and specific perfusion control of bioreactors based on the Aquasant probe were achieved. Implementation of cell density probe based perfusion control, instead of “step perfusion adjustments” based on manual hemacytometer control, will result in smoother operation, healthier cultures, increased medium delivery efficiency, and reduced operational excursions. © 1995 John Wiley & Sons, Inc.
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    Cometabolic degradation of trichloroethylene in a bubble column bioscrubber (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 461-469 
    Details
    ISSN: 0006-3592
    Keywords: trichloroethylene ; bioscrubber ; bubble column ; cometabolism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bubble column bioreactor was used as bioscrubber to carry out a feasibility study for the cometabolic degradation of trichloroethylene (TCE). Phenol was used as cosubstrate and inducer. The bioreactor was operated like a conventional chemostat with regard to the cosubstrate and low dilution rates were used to minimize the liquid outflow. TCE degradation measurements were carried out using superficial gas velocities between 0.47and 4.07 cm s-1 and TCE gas phase loads between 0.07 and 0.40 mg L-1 Depending on the superficial gas velocity used, degrees of conversion between 30% and 80% were obtained. A simplified reactor model using plug flow for the gas phase, mixed flow for the liquid phase, and pseudo first order reaction kinetics for the conversionof TCE was established. The model is able to give a reasonable approximation of the experimental data. TCE degradation at the used experimental conditions is mainly limited by reaction rate rather than by mass transfer rate. The model can be used to calculate the reactor volume and the biomass concentration for a required conversion. © 1995 John Wiley & Sons Inc.
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    Recombinant cyclin E expression activates proliferation and obviates surface attachment of chinese hamster ovary (CHO) cells in protein-free medium (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 476-482 
    Details
    ISSN: 0006-3592
    Keywords: cyclin E expression ; CHO cells ; insulin ; fibroblast growth factor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Exogenous growth factors normally required in cell culture activate cell proliferation via the molecular controls of cell-cycle progression. Highly differing influences of mitogenic stimulation of Chinese hamster ovary (CHO) cells by insulin and basic fibroblast growth factor(bFGF) have been clearly observed in a defined protein-free medium. CHO K1 cells stimulated only with insulin grow with flattened cell morphology and extensive cell-cell contact, whereas stimulation with only bFGF or bFGF plus insulin results in loss of cell-cell contact and a transformed and rounded-up morphology. Compared with insulin-stimulated cells, bFGF-stimulated cells exhibit a relatively long G1, and short S phase, and contain higher levels of cyclin E. Observation of elevated levels of cyclin E in wild-type CHO K1 cells mitogenically stimulated by basic fibroblast growth factor motivated transfection of these cells by a cyclin E expression vector. These transfectants grew rapidly in protein-free basal medium and had similar cyclin b levels, distributions of nuclear cell-cycle times, and cell morphologies as bFGF-stimutated CHO K1 culture. Metabolic engineering of cell-cycle regulation thus bypasses exogenous growth factor requirements, addressing a priority objective in economical, reproducible, and safe biopharmaceutical manufacturing. © 1995 John Wiley & Sons Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995) 
    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.260470501
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    Sustained and constitutive high levels of protein production in continuous cultures of bacillus subtilis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 520-524 
    Details
    ISSN: 0006-3592
    Keywords: bacillus subtilis ; plasmid ; continuous culture ; CAT ; recombinant cultures ; acid formation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The feasibility of continuous production of proteins in chemostat cultures of Bacillus subtilis was investigated. An expression system consisting of the bacterium B. subtilis BR151 carrying plasmid p602/19 was used. The plasmid contains the cat (chioramphenicol acetyltrans-ferase) gene downstream of a strong vegetative T5 promoter. It was found that, at a dilution rate of 0.2 h-1 production of relatively high levels of CAT protein (about 4% ofcellular protein) can be sustained. But, experiments at a higher dilution rate of 0.4 h-1 were unproductive because of high acidformation and washout. Combination of low cell yield, which results from excessive acid formation, and low dilution rate led to a low volumetric CAT productivity. Our recent work with the nonrecombinant cells, has demonstrated that uptake of small amounts of citrate significantly reduces or entirelyeliminates the acid formation. This superior performance in the presence ofcitrate was hypothesized, based on strong experimental evidence, to be the result of a reduction in glycolysis flux through a sequence of events leading to a reduction in pyruvate kinase and phosphof- ructokinase activities, the regulatory enzymes of glycol-ysis. In this study, it is demonstrated that cofeeding of glucose and citrate substantially reduces theorganic acid formation and significantly increases the recombinant culture productivity. The combination of high specific CAT activity and cell density resulted in a total of six- to tenfold higher culture productivitywhen citrate and glucose were cometabolized than when glucose was the only carbon source. © 1995 John Wiley & Sons Inc.
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    Membrane anchored protein production from spheroid, porous, and solid microcarrier chinese hamster ovary cell cultures (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 550-556 
    Details
    ISSN: 0006-3592
    Keywords: spheroids ; porous and solid microcarriers ; CHO ; controlled release ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of the microcarrier type on the performance of a controlled release process used to produce a recombinant glycosyl-phosphatidylinositol anchored protein was investigated. Chinese hamster ovary (CHO) cells expressing the human melanoma tumor antigen (p97) were cultured in 10% serum on Cultispher-GH porous microcarriers and then, for protein production, maintained in 2% serum. Cells were harvested every 48 h and p97 was recovered at 90 μg/mL and 40% purity. Harvested p97 concentrations were increased by harvestingfrom spheroid (241 μg/mL) and smaller porous microcarrier, Cultispher-G (167 μg/mL) cultures. The low total cell specific p97 production of cells cultured on Cultispher-GH was due to necrosis of cells within the beads, decreased p97 expression of the immobilized cells, dilution by the liquid (up to 40% volume) associated with settled beads, and incomplete recovery of p97 from within the beads. Cells cultured on solid microcarriers, Cytodex-1, had the highest cell viability and cell specific p97 production, It is recommended that a two-stage cyclic harvesting process of cells cultured on small Cultispher-G or on Cytodex-1 beads would minimize protein loss and maximize cell specific protein recovery. © 1995 John Wiley & Sons Inc.
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    Modeling of continuous Ph-stat stirred tank reactor with Lactococcus lactis ssp. lactis bv. diacetylactis immobilized in calcium alginate gel beads (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 567-574 
    Details
    ISSN: 0006-3592
    Keywords: immobilized Lactococcus diacetylactis ; alginate beads ; diffusionl/reactionl/growth model ; lactosecitrate cometabolism ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic diffusion-reaction-growth model is proposed for the study of lactic fermentation, the bioconversion of citric acid, and cell release in an immobilized cell reactor [pH-stat continuous stirred tank-reactor (CSTR)]. The model correctly simulates the onset of fermentation and colonization of the gel, followed by the steady state. External diffusion is nonlimiting and internal diffusion is limited by high cell densities at the periphery of the gel beads. Lactose-citrate cometabolism in the gel is related to the distribution of active included biomass within the gel and to gradients of substrates (lactose, citrate) and products (lactate, pH) in the beads. The utilization of lactose is limited by reaction, whereas that of citrate is limited by diffusion. Cell release from gel to the liquid medium occurs in the external spherical cap of the beads. In this peripheral zone viability is maintained at around 90%. © 1995 John Wiley & Sons Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995) 
    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.260470601
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    Cross-flow ultrafiltration of proteins through asymmetric polysulfonic membranes: I. Retention curves and pore size distributions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 617-625 
    Details
    ISSN: 0006-3592
    Keywords: cross-flow ultrafiltration ; polysulfonic membranes ; proteins ; concentration-polarization ; pore size distributions ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flux and retention of 0.1%w/w aqueous solutions of several proteins [lysozyme, pepsin, bovine serum albumin (BSA), lipase, and γ-globulin] with molecular weights of 14.6, 36, 67, 801 and 150 kDa are studied when they are tangentially filtered, with transmembrane pressure differences until 1 MPa and circulation velocities in the re-tentate loop from 0.04 to 1.98 m/s (laminar regime), through two asymmetric polysulfone commercial membranes (E-100 with a nominal pore size of 0.01 μm and E-500 with a nominal pore size of 0.04 μm). Results are analyzed with the film theory for the concentration-polarization phenomenon, obtaining the mass transfer coefficient along with the apparent and true retention coefficients for the cell used, as a function of the feed circulation velocity and the molecular weight of the solute. The standard retention curves lead to pore size distributions differing from the nominal ones. These differences can be attributed to the modifications of the membranes when they are in operational conditions, probably due to protein adsorption. © 1995 John Wiley & Sons, Inc.
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    On the use of the pH control reagent addition rate for fermentation monitoring (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 651-665 
    Details
    ISSN: 0006-3592
    Keywords: abiotic proton balance ; acid, base ; bicarbonate buffer system ; fermentation ; pH ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The linear relation between the pH control reagent addition rate, the net conversion rates of metabolites, the carbon dioxide mass transfer rate and the feed rates is developed and shown to have the same form for batch, fed-batch, and continuous reactors, regardless of the number of feeds. The magnitudes of various biological and solution chemistry effects on the pH control reagent addition rate are estimated to be negligible, facilitating the use of the pH control reagent addition rate as a straightforward indicator of primary metabolism. Finally, application of the linear relation, termed the abiotic proton balance, is discussed for a number of fermentation processes. © 1995 John Wiley & Sons, Inc.
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    Taxol production in bioreactors: Kinetics of biomass accumulation, nutrient uptake, and taxol production by cell suspensions of Taxus baccata (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 666-676 
    Details
    ISSN: 0006-3592
    Keywords: taxol ; plant cell culture ; bioreactors, kinetics ; Taxus baccata ; secondary metabolite ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of biomass accumulation, nutrient uptake and taxol production of Taxus baccata cell suspensions were examined in three bioreactor configurations, viz. 250-mL Erienmeyerflasks, 1-L working volume pneumatically mixed (PMB), and stirred tank (STB) bioreactors. Qualitatively similar kinetics were observed in all three bioreactor types. Biomass accumulation and specific nutrient uptake rates exhibited biphasic characteristics. Carbohydrate uptake and biomass accumulation substantially ceased when phosphate was depleted from the medium. Phosphate was identified as a possible growth-limiting nutrient. Taxol accumulated exclusively in the second phase of growth. A maximum taxol concentration of 1.5 mg/L was obtained in the PMB which was fivefold greater than that obtained in the Erienmeyer flasks and the STB, but the relative kinetics of taxol production was the same in all three reactor types. Biomass yields were calculated from the kinetic data and a stoichiometry for biomass formation was evaluated. The similarity of kinetics in the three bioreactor configurations suggests that taxol production by T. baccata cell suspensions is amenable to scateup. © 1995 John Wiley & Sons, Inc.
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    Use of comparative reasoning tools for evaluation of the effect of sterilization conditions on fermentations to produce acidic fibroblast growth factor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 688-695 
    Details
    ISSN: 0006-3592
    Keywords: acidic fibroblast growth factor ; Escherichia coli ; sterilization ; comparative reasoning tools ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of various medium sterilization conditions on fermentations of a recombinant, acidic fibroblast growth factor (aFGF) producing Escherichia coli have been studied. Changes in the medium resulting from sterilization were monitored by pH and absorption spectra. This simple experiment provided excellent data for the demonstration of the usefulness of comparative reasoning tools in order to evaluate the effect of sterilization on fermentation performance. The time profiles of the main parameters (e.g., carbon dioxide evolution rate, dissolved oxygen, pH, and aFGF productivity) were simplified into piecewise contiguous linear segments, each of which was sequentially numbered. The length, position, and slope of each tine were then characterized. Application of the comparative reasoning tools confirmed that separate sterilization of the glucose was necessary for the success of the process, despite adding to the cost and complexity. The comparative data analysis also showed that scaleup with longer sterilization holding and cooling times would not be detrimental to aFGF production. © 1995 John Wiley & Sons, Inc.
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    Announcement from the publisher (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. ii 
    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.260480102
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    Modeling biofilm accumulation and mass transport in a porous medium under high substrate loading (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 47 (1995), S. 703-712 
    Details
    ISSN: 0006-3592
    Keywords: biofilm modeling ; detachment ; porous media ; biobarriers ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A packed bed biofilm reactor inoculated with pure culture Pseudomonas aeruginosa was run under high substrate loading and constant flow rate conditions. The 3.1-cm-diameter cylindrical reactor was 5 cm in length and packed with 1-mm glass beads. Daily observations of biofilm thickness, influent and effluent glucose substrate concentration, and effluent dissolved and total organic carbon were made during the 13-day experiment. Biofilm thickness appeared to rech quasi-steady-state condition after 10 days. A published biofilm process simulation program (AQUASIM) was used to analyze experimental data. Comparison of observed and simulated variables revealed three distinct phases of biofilm accumulation during the experiment: an initial phase, a growth phase, and a mature biofilm phase. Different combinations of biofilm and mass transport process variables were found to be important during each phase. Biofilm detachment was highly correlated with shear at the biofilm surface during all three phases of biofilm development. © 1995 John Wiley & Sons, Inc.
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    Characterization of an oligonucleotide-binding fluorescent ligand for application in affinity purification of dsDNA (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 25-35 
    Details
    ISSN: 0006-3592
    Keywords: DNA purification ; DNA-binding fluorophore ; Fluorescent ligand ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The fluorescent probe PO-PRO-3 was investigated as a potential ligand for the affinity immobilization and purification of genomic or plasmid DNA fragments. Affinities and mechanisms for PO-PRO-3 binding to superhelical and linearized pUC 18 plasmid DNA were examined through measurement of binding isotherms, continuous-variation analysis, and DNA titrations. In addition, the effects of DNA conformation, protein and RNA contaminants, solvent polarity, and ionic strength are examined with the aim of optimizing binding and elution conditions and of assisgning limits to the range of applicability of the affinity purification. © 1995 John Wiley & Sons, Inc.
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    Implantable hollow fiber bioreactor as a potential treatment for hypercholesterolemia: Characterization of the catalytic unit (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 36-41 
    Details
    ISSN: 0006-3592
    Keywords: hollow fiber ; bioreactor ; immobilized enzymes ; porosity ; phospholipase A2 ; low densitylipoprotein ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous studies have shown that the modification of low density lipoprotein (LDL) by the enzyme phospholipase A2(PLA2)results in a reduction of cholesterol levels in the plasma of hypercholesterolemic rabbits, due to accelerated clearance of the modified LDL. In the current study, we established techniques and optimized the ratio of enzyme to support for the immobilization of PLA2 on a polymeric support. Hollow fiber bioreactors made from polytetrafluoroethylene (PTFE) polymers were used to encapsulate immobilized PLA2. This design was adopted to eliminate hemolysis of red blood cells by the enzyme. Characterization of the resulting immobilized enzyme in terms of its activity, Michaelis-Menten kinetic constants, and the variation of its activity with incubation time is presented. The enzyme activity was not significantly altered upon incubation at 37°C in lipoprotein-deficient serum (LPDS), over the course of 2 months. The Michaelis-Menten kinetics constants are KM = 8.9 mM, Vmax = 6434.2 for the free enzyme and KappM = 16.7 mM, Vappmax = 619.7 for the immobilized enzyme. These data suggest that a system based on immobilized PLA2 in conjunction with hollow fiber bioreactors (HFBs) may be a good candidate for lowering LDL levels in plasma. © 1995 John Wiley & Sons, Inc.
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    A synthetic medium for continuous culture of the S-layer carrying Bacillus stearothermophilus PV 72 and studies on the influence of growth conditions on cell wall properties (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 66-77 
    Details
    ISSN: 0006-3592
    Keywords: crystalline surface layers ; synthetic medium ; Bacillus stearotherrnophilus ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bacterial cell surface layers (S-layers) which show a crystalline structure, defined pores, and a regular arrangement of functioal groups can be used for production of isoporous ultrafiltration membranes and as a matrix for immobilization of macromolecules. S-layer-carrying cell wall fragments from thermophilic Bacillaceae possess an extremely thin peptidoglycan-containing layer with pores larger than those in the S-layer lattice. Thus, they can directly be used for biotechnological applications, when an S-layer protein pool is stored in the rigid cell wall layer which is released during cell wall preparation, forming an inner S-layer. In the present study, a synthetic medium for Bacillus stearothermophilus PV 72 was developed by applying the pulse and shift technique with the aim to produce cell wall fragments with before-mentioned properties by varying the growth conditions in condtinuous culture. The organism was grown at 57°C in a bioreactor with 1 L working volume equipped with exhaust gas analysis and connected to a PC-based process control system. Biomass concentration was 2.2 g/L out of 8 g/L glucose at a dilution rate of 0.3 h-1, giving a biomass productivity of 0.66 g/L h. Although the organism was grown under different conditions, no change in peptidoglycan composition, extent of peptidoglycan crosslinking, and content of secondary cell wall polymers was observed. The amount of S-layer protein pool stored in the rigid cell wall layer and the autolytic activity depended mainly on the specific growth rate. Cell wall fragments with properties required for ultrafiltration membrane production could be produced by parameter settings in continuous culture. © 1995 John Wiley & Sons, Inc.
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    Enzyme-mediated proteolysis of fibrous biopolymers: Dissolution front movement in fibrin or collagen under conditions of diffusive or convective transport (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 89-107 
    Details
    ISSN: 0006-3592
    Keywords: fibrin ; collagen ; proteolysis ; plasminogen ; diffusion ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A numerical model based on the convective-diffusive transport of reacting and adsorbing proteolytic enzymes within erodible fibrous biopolymers was used to predict lysis fronts moving across biogels such as fibrin or collagen. The fiber structure and the transport properties of solutes in fibrin (or collagen) were related to the local extent of dissolution within the dissolving structure. An accounting for solubilization of adsorbed species into solution from the eroding fiber phase provided for complete conservation of mass in reacting systems containing over 10 species. At conditions of fibrinolysis typical of clinical situations, the model accurately predicted the dynamic rate of lysis front movement for plasmin, urokinase, and tissue plasminogen activator (tPA)-mediated lysis of fibrin gels measured in vitro. However, under conditions of extremely fast fibrinolysis using high enzyme concentrations, fibrinolytic fronts moved very rapidly (〉0.1 mm/mm) - faster than predicted for diffusionlimited reactions - at nearly constant velocity for over 2 h, indicating non-Fickian behavior. This was due to proteolysis-mediated retraction of dissolving fibrin fibers that resulted in fiber convection and front-sharpening within 3 μm of the reaction front, as observed by digitally enhanced microscopy. In comparing the model to fibrinolysis measurements using human lys77-plasmin, the average first order rate constant for non-crosslinked fibrin bond cleavage by fibrin-bound plasmin was calculated to be 5s-1 assuming that 10 cleavages per fibrin monomer were required to solubilize each monomer. The model accurately predicted lysis front movement using pressure-driven permeation of plasmin or urokinase into fibrin as well as literature data obtained under well- mixed conditions for tPA-mediated fibrinolysis. This numerical formulation provides predictive capability for optimization of proteolytic systems which include thrombolytic therapy, wound healing, controlled drug release, and tissue engineering applications. © 1995 John Wiley & Sons, Inc.
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    Gas phase composition effects on suspension cultures of Taxus cuspidata (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 123-132 
    Details
    ISSN: 0006-3592
    Keywords: secondary metabolite ; taxol ; ethylene ; carbon dioxide ; oxygen ; taxus cuspidata ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of different concentrations and combinations of oxygen, carbon dioxide, and ethylene on cell growth and taxol production in suspension cultures of Taxus cuspidata was investigated using several factorial design experiments. Low head space oxygen concentration (10% v/v) promoted early production oftaxol. High carbon dioxide concentration (10% v/v) inhibited taxol production. The most effective gas mixture composition in terms of taxol production was 10% (v/v) oxygen, 0.5% (v/v) carbon dioxide, and 5 ppm ethylene. Cultures grown underambient concentration of oxygen had a delayed uptake of glucose and fructose compared to cultures grown under 10% (v/v) oxygen. Average calcium uptake rates into the cultured cells decreased and average phosphate uptake rates increased as ethylene was increased from 0 to 10 ppm. These results may indicate that gas composition alters partitioning of nutrients, which in turn affects secondary metabolite production. © 1995 John Wiley & Sons, Inc.
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    Studies on the synthesis of βhCG hormone in vero cells by recombinant vaccinia virus (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 158-168 
    Details
    ISSN: 0006-3592
    Keywords: Vero ; vaccinia virus expression ; MOI ; βhCG ; mRNA ; immunoligical and biological activity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Synthesis of the β-subunit of human chorionic gonado-tropin (βhCG) in Vero cells by the recombinant vaccinia virus has been studied. The yield of βhCG was a function of the multiplicity of infection (MOI), and was highest at 25 MOI. The kinetics of synthesis and initial secretion of βhCG, deduced from the pulse-chase experiments were “zero order.” At 30 h postinfection, the relative values of net synthesis and secretion rates were 4.0 AU. mm2 βhCG/106 cells. h and 1.55 AU. mm2 βhCG/106 cells. h, respectively. The time required to secrete 50% of intracellular βhCG was 210 min. Pulse-chase data also showed that 24% of βhCG was degraded intracelluiarly within 10 h, of which 17% was detected in the autoradiogram. Along with 30 kD βhCG, a satellite band of 28 kD was evident among the peptide synthesized in Vero cells. The molecular weight of vaccinia-derived βhCG was 13 kD more that its nonglycosylated form, indicating extensive glycosylation in Vero cells. The mRNA levels in infected Vero cells at different postinfection times were quantified by excess DNA dot-blot hybridization. It appears that the Vero cell possesses some host cell-associated factor(s), which prevented the transcription of early βhCG-mRNA promoted by the early signal of the vaccinia P 7.5 promoter. The half-life of βhCG-mRNA, as determined by follow-up of decay after blocking transcription initiation, was found to be 6.4 h. The synthesized βhCG was immunoreactive as it reacted with monoclonal and polyclonal monospecific antibodies. The subunit was also biologically active, as it combined with native βhCG to form heterodimer βhCG, which competed with 125I-hCG for radioreceptors and stimulated testosterone synthesis in Leydig cells. © 1995 John Wiley & Sons, Inc.
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    Thermodynamic and kinetic parameters of lipase-catalyzed ester hydrolysis in biphasic systems with varying organic solvents (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 179-189 
    Details
    ISSN: 0006-3592
    Keywords: biphasic system ; activity coefficient ; organic solvents ; solvation ; hydrolysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetics of lipase-catalyzed hydrolysis of esters were modeled using reactant activities for aqueous-organic, biphasic systems. By using thermodynamic activities of the substrates in ordinary rate equations, the kinetic parameters were corrected for the contribution of substrate-solvent interactions and a uniform quantification of the substrates for lipase attached to the interface can be achieved. The kinetic parameters, on the basis of their thermodynamic activities, should be constant in different systems, provided that the solvents do not interfere with the binding of the substrates to the enzyme nor affect the catalytic mechanism. Experimental and computational methods on how to obtain the thermodynamic activities of the substrates are presented. Initial rates were determined for Pseudomonas cepacia lipase (PcL)-catalyzed hydrolysis of decyl chloroacetate in dynamic emulsions with various solvents. The thermodynamic equilibrium and corrected kinetic constants for this reaction appeared to be similar in various systems. The kinetics of PcL in an isooctane-aqueous biphasic system could be adequately described with the rate equation for a ping-pong mechanism. The observed inhibitory effect of decanol appeared to be a consequence of this mechanism, allowing the backreaction of the decanol with the chloroacetyl-enzyme complex. The kinetic performance of PcL in systems with toluene, dibutyl ether, and methyl isobutyl ketone could be less well described. The possible causes for this and for the remaining differences in corrected kinetic parameters are discussed. © 1995 John Wiley & Sons, Inc.
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    Fed-batch culture of Bacillus thuringiensis for thuringiensin production in a tower type bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 207-213 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus thuringiensis ; glucose ; thuringiensin production ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fed-batch culture of Bacillus thuringiensis in a modified airlift reactor has been developed by using adaptive control of glucose concentration in the reactor. The glucose concentration was estimated via a correlation equation between carbon dioxide production rate and glucose consumption rate. The estimated glucose concentration as the output variable was fed back to computer for calculation of substrate addition. The modified reactor was an airlift reactor with a net draft tube. The airlift reactor had high oxygen transfer rate and low shear stress which were important factors for production of thuringiensin. Fed-batch culture of Bacillus thuringiensis in the modified airlift reactor provided significant improvement of thuringiensin production. © 1995 John Wiley & Sons, Inc.
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    A metabolic model of the biological phosphorus removal process: II. Validation during start-up conditions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 234-245 
    Details
    ISSN: 0006-3592
    Keywords: phosphorus removal, biological ; metabolic model ; polyphosphate ; PHB, ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A metabolic model of the biological phosphorus removal process has been developed and validated previously for complex conversions during the process under anaerobic and aerobic conditions at different growth rates in sequencing batch reactors in steady state. For additional validation of the metabolic model, the model was applied to the dynamic conditions which occur during the start-up phase of the biological P removal in the presence and absence of non-polyP heterotrophic microorganisms. In a laboratory scale sequencing batch reactor, experiments were performed to examine the enrichment of the population with polyphosphate organisms during the start-up and the subsequent shift from non-polyP, heterotrophic organisms to polyP organisms in the sludge. The effect of different influent loading patterns for acetate and phosphate was studied. In these experiments, the maximal growth rate of the polyP organisms and the behavior of the internal storage compounds could be derived. The metabolic model was capable of describing the experimental results, without the need to adjust the kinetic or stoichiometric parameters obtained under steady state conditions. © 1995 John Wiley & Sons, Inc.
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995) 
    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.260480401
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    Biomimetic-dye affinity adsorbents for enzyme purification: Application to the one-step purification of Candida boidinii formate dehydrogenase (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 278-288 
    Details
    ISSN: 0006-3592
    Keywords: affinity chromatography ; biomimetic dye ; Candida boidinii ; enzyme purification ; oformate dehydrogenase ; triazine dye ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Formate dehydrogenase (FDH, EC 1.2.1.2) was purified from Candida boidinii cells in a single step by biomimetic-dye affinity chromatography. For this purpose, seven' biomimetic analogues of the monochlorotriazine dye, Cibacron® Blue 3GA (CB3GA), and parent dichloro-triazine dye, Vilmafix® Blue A-R (VBAR), bearing a car-boxylated structure as their terminal biomimetic moiety, were immobilized on crosslinked agarose gel, Ultrogel® A6R. The corresponding new biomimetic-dye adsorbents, along with nonbiomimetic adsorbents bearing CB3GA and VBAR, were evaluated for their ability to purify FDH from extracts obtained after press-disintegration of C. boidinii cells. Optimal conditions for maximizing specific activity of FDH in starting extracts (1.8 U/mg) were realized when cell growth was performed on 4% methanol, and press disintegration proceeded in four consecutive passages before the homogenate was left to stand for 1 h (4°C). When compared to nonbiomimetic adsorbents, biomimetic adsorbents exhibited higher purifying ability. Furthermore, one immobilized biomimetic dye, bearing as its terminal biomimetic moiety mercap-topyruvic acid linked on the chlorotriazine ring (BM6), displayed the highest purifying ability. Adsorption equilibrium data which were obtained for the BM6 adsorbent in a batch system corresponded well to the Langmuir isotherm and, in addition, breakthrough curves were taken for protein and FDH adsorption in a fixed bed of BM6 adsorbent. The dissociation constant ( KD) of the complex between immobilized BM6 and FDH was found to equal 0.05 μM. Adsorbent BM6 was employed in the purification of FDH from a 18-L culture of C. boidinii in a single step (60% overall yield of FDH). The purified FDH afforded a single-band on sodium dodecyl sulphate poly-acrylamide gel electrophoresis, and a specific activity of 7,0 U/mg (30°C). © 1995 John Wiley & Sons, Inc.
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    Metal affinity protein precipitation: Effects of mixing, protein concentration, and modifiers on protein fractionation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 324-332 
    Details
    ISSN: 0006-3592
    Keywords: plasma fractionation ; mixing ; protein precipitation ; metal affinity ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous work by us and others has shown that mixing impacts apparent protein solubility in single protein precipitations. In this work, we probe the effects of contacting conditions on fractional precipitation behavior at the bench scale. We have chosen metal affinity precipitation as our model system; the kinetics of this mode of precipitation are very rapid and largely irreversible and, consequently, mixing conditions govern the extent of fractionation and purity of the product in such a process. Our experimental strategy involved a three-pronged approach to control the effects contacting conditions on precipitate yield, purity, and particle size distribution. First, we studied the impact of process variables that control precipitant concentrations in the reactor including impeller speed and precipitant addition rate. Second, we controlled the rate of precipitation by changing the initial protein concentration to alter the protein-protein collision rate. Third, we examined the role of the molecular-level kinetics of affinity precipitation by using modifiers that compete with surface moieties to bind the metal ion, thereby reducing its availability. Our model process and protein system consisted of zinc precipitations of mixtures of bovine serum albumin and bovine γ-globulins, carried out at a nominal 1-L scale; glycine was examined as a modifier. Faster impeller speeds and lower precipitant addition rates increased the desired protein yields, decreased purities, and reduced average precipitate particle size. Higher initial protein concentrations were found to produce precipitates with higher yields, lower purities and diminished particle size. Experiments with glycine indicated that modifiers in the precipitant solution serve to increase product purity, decrease yield, and increase the average particle size in bench-scale precipitations. © 1995 John Wiley & Sons, Inc.
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    Surfactant structure effects in protein separations using nonionic microemulsions (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 99-108 
    Details
    ISSN: 0006-3592
    Keywords: microemulsions, nonionic ; protein, separations ; sorbitan esters ; alkyl ethoxylates ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this article, the extraction of cytochrome c utilizing various nonionic surfactant microemulsions has been tested to determine the effect of surfactant structure on protein partitioning. Surfactants tested include a linear alcohol ethoxylate (Neodol 91-2.5), two alkyl phenol ethoxylates (lgepal CO-520, Trycol 6985), and a series of alkyl sorbitan esters that are either ethoxylated (Tweens) or un-ethoxylated (Spans). Initial attempts to extract hemoglobin into Neodol 91-2.5 Winsor II microemulsions (oil-continuous) appeared successful based on heme estimation. Careful analysis showed that the hemoglobin had dissociated prior to extraction and that only the heme was extracted with false positive results. In fact, Neodol 91-2.5 microemulsions were unable to extract a variety of proteins with differing biophysical properties. Among all the other nonionic surfactant microemulsions tested only those made using sorbitan esters extracted significant amounts of cytochrome c. The partition coefficients achieved in this study are more than an order of magnitude higher than that seen previously in the literature for comparable sorbitan systems. However, this partition coefficient is extremely sensitive to ionic strength. At an ionic strength as low as 0.001 M, the partition coefficient is reduced to that seen in previous studies. We have found that protein partitioning in sorbitan ester microemulsions is not a function of water content. In addition, extraction is not a function of either alkyl chain length, or polyethylene oxide molecular weight. Hence, the sorbitan group appears to have an important role in extraction, possibly through a weak electrostatic protein-surfactant interaction. © 1995 John Wiley & Sons, Inc.
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    Enzymatic glucosylation of hydrophobic alcohols in organic medium by the reverse hydrolysis reaction using almond-β-D-glucosidase (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 109-116 
    Details
    ISSN: 0006-3592
    Keywords: glucosylation ; alcohol ; hydrolysis, reverse ; galactoside ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alkyl β-D-glucosides were synthesized from D-glucose and alcohols by reverse hydrolysis using the commercially available almond β-D-glucosidase in 9:1 (v/v) acetonitrile-water medium. The main characteristics of this enzyme-catalyzed glucosylation were established by using 2-hydroxybenzyl alcohol. The reaction is entirely regio- and stereoselective. The solvent plays a fundamental role because, by decreasing the water concentration in the medium, the shift of the reaction equilibrium toward synthesis is realized without using an excessive amount of alcohol. Nevertheless, a minimum amount of water is necessary to maintain the enzyme activity. In contrast to the use of the enzyme in aqueous medium, the pH of the added water in acetonitrile did not influence the synthesis. Using this procedure, we have conducted systematic glucosylation of numerous alcohols and we have investigated enzyme specificity and alcohol reactivity. The enzyme has a pronounced affinity for the alcohols containing a phenyl group, and enantioselectivity for the aglycon is obtained with 1-phenylethyl alcohol. Moreover, by using almond β-D-glucosidase it was also possible to synthesize alkyl β-D-galactosides. © 1995 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1002/bit.260460204
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    Photochemistry of a photosynthetic reaction center immobilized in lipidic cubic phases (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 93-98 
    Details
    ISSN: 0006-3592
    Keywords: photosynthetic reaction center ; liquid crystals ; cubic phases ; immobilization ; Chloroflexus aurantiacus ; photochemistry ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Photosynthetic reaction centers, isolated and purified from the facultative phototrophic bacterium Chloroflexus aurantiacus, were immobilized in optically transparent lipidic cubic phases composed of 42% (w/w) 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine and 58% (w/w) water. The immobilized photosynthetic protein retains its native properties, as indicated by visible and circular dichroic spectra. The ground state visible spectrum of the immobilized reaction centers is very similar to the corresponding spectrum in aqueous solution, indicating that the protein pigments are not extracted into the lipidic regions of the cubic phase. The secondary structure of the protein is maintained in the immobilized state, as determined by far-UV circular dichroism spectroscopy in the 200- to 250-nm range. Moreover, immobilized reaction centers retain their photochemical activity: a reversible photo-oxidation of the primary electron donor (P) is seen upon continuous illumination. Furthermore, the entrappment of reaction centers does not affect the kinetics of charge recombination between the photo-oxidized primary donor (P+) and the photoreduced primary quinone acceptor, generated by a short flash of light. Reaction centers devoided of the secondary quinone acceptor can be easily reconstituted in cubic phases by means of their coimmobilization with 1,4-naphtoquinone. Indeed, the kinetics for charge recombination in reconstituted reaction centers is dramatically slower than the corresponding kinetics in the unreconstituted protein. Interestingly, immobilized reaction centers are significantly stabilized as compared with reaction centers in aqueous solution: the integrity of the protein in the cubic phase is maintained for at least 5 months, whereas in water solution 50% of the activity is lost within 2 months. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460202
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    Assessment of a disc stack centrifuge for use in mammalian cell separation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 132-138 
    Details
    ISSN: 0006-3592
    Keywords: centrifuge ; disk stack ; mammalian cell separation ; hybridoma cells ; cell harvest ; debris ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A prototype disc stack centrifuge was tested for the separation of mammalian cell cultures from 80- and 2000-L fermentations. The clarification capacity for mammalian cells was excellent, but some smaller particles remained in the supernatant and reduced its usefulness for downstream processing. In order to identify the source of such particle formation, several parameters were assessed and minimum particle size for separation was calculated. An analysis of particle distribution was performed. Temperature and pressure effects inside the centrifuge bowl were measured. Some modifications of mechanical engineering can be suggested for the improvement of the use of standard disc stack centrifuges for mammalian cells. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460206
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    Development of a predictive description of an immobilized-cell, three-phase, fluidized-bed bioreactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 139-146 
    Details
    ISSN: 0006-3592
    Keywords: fluidized-bed bioreactor ; concentration profile ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fully predictive mathematical description of a three-phase, tapered, fluidized-bed bioreactor is developed. This mathematical model includes the effects of the tapered bed, variable dispersion coefficient, and variable solid holdup upon the concentration profiles developed in the bed. In addition, the effect of the concentration profile which is developed inside the biocatalyst bead is included by means of an effectiveness factor calculation. Using accepted correlations for the dispersion coefficient and for the liquid, gas, and solid holdup in the bed, the model is fully predictive. The model was found to adequately predict experimental obtained concentration profiles. Then, the model was used to examine the various phase holdups through the bed and the degree to which the dispersion coefficient varied through the bed. The effect of changes in these calculated variables upon the reaction rate is discussed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460207
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    Heterogeneity within populations of recombinant Chinese hamster ovary cells expressing human interferon-γ (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 147-158 
    Details
    ISSN: 0006-3592
    Keywords: CHO cell ; cell aggregation ; recombinant human interferon-γ ; mammalian cell culture ; cell culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Chinese hamster ovary (CHO) cell line has great commercial importance in the production of recombinant human proteins, especially those for therapeutic use. Much attention has been paid to CHO cell population physiology in order to define factors affecting product fidelity and yield. Such studies have revealed that recombinant proteins, including human interferon-γ (IFN-γ), can be heterogeneous both in glycosylation and in proteolytic processing. The type of heterogeneity observed depends on the growth physiology of the cell population, although the relationship between them is complex. In this article we report results of a cytological study of the CHO320 line which expresses recombinant human IFN-γ. When grown in suspension culture, this cell line exhibited three types of heterogeneity: (1) heterogeneity of the production of IFN-γ within the cell population, (2) heterogeneity of the number of nuclei and mitotic spindles in dividing cells, and (3) heterogeneity of cellular environment. The last of these arises from cell aggregates which form in suspension culture: Some cells are exposed to the culture medium; others are fully enclosed within the mass with little or no direct access to the medium. Thus, live cells producing IFN-γ are heterogeneous in their environment, with variable access to O2 and nutrients. Within the aggregates, it appears that live cells proliferate on a dead cell mass. The layer of live cells can be several cells deep. Specific cell-cell attachments are observed between the living cells in these aggregates. Two proteins, known to be required for the formation of certain types of intercellular junctions, spectrin and vinculin, have been localized to the regions of cell-cell contact. The aggregation of the cells appears to be an active process requiring protein synthesis. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460208
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    Metabolic flux distributions in Penicillium chrysogenum during fed-batch cultivations (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 117-131 
    Details
    ISSN: 0006-3592
    Keywords: biochemical model ; Penicillium chrysogenum ; flux analysis ; penicillin ; metabolic engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Based on a review of the Penicillium chrysogenum biochemistry a stoichiometric model has been set up. The model considers 61 internal fluxes and there are 49 intracellular metabolites which are assumed to be in pseudo-steady state. In addition to the intracellular fluxes the model considers the uptake of 21 amino acids. From the stoichiometric model the maximum theoretical yield of penicillin V is calculated to 0.43 mol/mol glucose. If biosynthesis of cysteine is by direct sulfhydrylation rather than by transsulfuration, the maximum theoretical yield is about 20% higher, i.e., 0.50 mol/mol glucose. The theoretical yield decreases substantially if α-aminoadipate is converted to 6-oxo-piperidine-2-carboxylic acid (OPC). If only 40% of the α-aminoadipate is recycled, the maximum theoretical yield is 0.31 mol/mol glucose. The uptake rates of glucose, lactate, γ-aminobutyrate, and 21 amino acids were measured during fed-batch cultivations. The rates of formation of penicillin V, δ-(L-α)-aminoadipyl-L-cysteinyl-D-valine (ACV), OPC, and the pool of isopenicillin N, 6-APA, and 8-HPA were also measured. Finally the synthesis rates of the biomass constituents RNA/DNA, protein, lipid, carbohydrate, and amino carbohydrate were measured. From these measured rates and the stoichiometric model the metabolic fluxes through the different intracellular pathways are calculated. The calculations show that penicillin formation is accompanied by a large flux through the pentose phosphate (PP) pathway due to a large requirement for nicotinamide-adenine dinucleotide phosphate (NADPH) used in the biosynthesis of cysteine. If cysteine is added to the medium, the flux through the PP pathway decreases. From the stoichiometric model YxATP is calculated to 87 mmol adenosine triphosphate (ATP)/g dry weight (DW), and from the flux calculations mATP is found to 3 mmol ATP/g DW/h. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460205
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    Reversed micellar extraction of trypsin: Effect of solvent on the protein transfer and activity recovery (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 172-174 
    Details
    ISSN: 0006-3592
    Keywords: reversed micelles ; extraction ; trypsin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: By using trypsin as the model protein and AOT as the model surfactant, the effect of a variety of solvents on protein transfer and activity recovery during the liquid-liquid reversed micellar extraction was investigated. It was found that several solvents, including isooctane, octane, heptane, and kerosene, had a similar effect on the recovery of trypsin activity after a full cycle of forward and backward extraction, and could all be used as the solvents for AOT-reversed micelles in trypsin extraction. Two other solvents (hexane and cyclohexane), however, were not so efficient. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460210
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    Reduction of nitrate and nitrite in a cyclically operated continuous biological reactor (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 159-171 
    Details
    ISSN: 0006-3592
    Keywords: denitrification ; nitrate ; nitrite ; cyclic bioreactors ; wastewater treatment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biological reduction of nitrate and nitrite was studied with a continuously operated cyclic reactor. The medium was fed to the reactor during the first phase of the cycle, and the effluent was drawn from the reactor during the third phase of the cycle; reaction occurred throughout the cycle. The process was described mathematically based on kinetic expressions revealed in an independent study. The model equations were subjected to detailed analysis with numerical codes based on the bifurcation theory for forced systems. The analysis has shown that in the operating parameter space there are extensive regions where the system can reach up to three different periodic states. The results of this analysis are shown in the form of two-dimensional operating diagrams. Numerical results have also shown that under certain operating conditions nitrate can be completely eliminated, while nitrite remains practically untreated. An experimental unit was designed, constructed, and used in experiments with a strain of Pseudomonas denitrificans [American Type Culture Collection (ATCC) 13867] under different operating conditions. The experimental results confirmed the theoretical predictions both qualitatively and quantitatively. Conditions under which complete reduction of both nitrate and nitrite is achieved, were found and experimentally verified. The results of this study suggest a methodology for analysis and design of cyclically operated bioreactors employed in denitrification of wastewaters. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460209
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    Masthead (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995) 
    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.260460301
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    The oxidation of chiral alcohols catalyzed by catalase in organic solvents (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 46 (1995), S. 175-179 
    Details
    ISSN: 0006-3592
    Keywords: catalase ; oxidation ; hydroperoxide ; enantioselectivity ; alcohol ; organic solvents ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The catalytic properties of bovine liver catalase have been investigated in organic solvents. In tetrahydrofuran, dioxane, and acetone (all containing 1% to 3% of water), the enzyme breaks down tert-butyl hydroperoxide several fold faster than in pure water. Furthermore, the rate of catalase-catalyzed production of tert-butanol from tert-butyl hydroperoxide increases more than 400-fold upon transition from aqueous buffer to ethanol as the reaction medium. The mechanistic rationale for this striking effect is that in aqueous buffer the rate-limiting step of the enzymatic process involves the reduction of catalase's compound I by tert-butyl hydroperoxide. In ethanol, and additional step in the reaction scheme becomes available in which ethanol, greatly outcompeting the hydroperoxide, is oxidized by compound I regenerating the free enzyme. In solvents, such as acetonitrile or tetrahydrofuran, which themselves are not oxidizable by compound I, catalase catalyzes the oxidation of numerous primary and secondary alcohols with tert-butyl hydroperoxide to the corresponding aldehydes or ketones. The enzymatic oxidation of some chiral alcohols (2,3-butanediol, citronellol, and menthol) under these conditions occurs enantioselectively. Examination of the enantioselectivity for the oxidation of 2,3-butanediol in a series of organic solvents reveals a considerable solvent dependence. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260460211
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    Protected amino acids as novel low-molecular-weight displacers in cation-exchange displacement chromatography (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 452-460 
    Details
    ISSN: 0006-3592
    Keywords: chromatography ; displacement ; protein purification ; cation exchange systems ; amino acid ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Although the ability to carry out simultaneous concentration and purification in a single displacement step has significant advantages for downstream processing of pharmaceuticals, a major impediment to the implementation of displacement chromatography has been the lack of suitable displacer compounds. An important recent advance in the state of the art of displacement chromatography has been the discovery that low-molecular-weight dendritic polymers can be successfully employed as displacers for protein purification in ion-exchange systems. In this article, protected amino acid esters (based on arginine and lysine) are shown to be useful displacers for protein purification in cation-exchange systems. A dynamic affinity plot is employed to evaluate the affinity of these low-molecular-weight compounds under dis-placement conditions. In contrast to large polyelectroyte displacers, the efficacy of these low-molecular-weight displacers was shown to be dependent on both the initial carrier salt concentration and the displacer concentration. In addition to the funcamental interest generated by low-molecular-weight displacers, it is likely that these displacers will have significant operatioal advantages as compared with large polyelectrolyte displacers. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bit.260480507
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