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  • 1
    Digitale Medien
    Digitale Medien
    Biocatalysis using gelatin microemulsion-based organogels containing immobilized Chromobacterium viscosum lipase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 53 (1997), S. 121-131 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biocalalysis ; microemulsion ; gelatin ; organogel ; lipase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Chromobacterium viscosum (CV) lipase was immobilized in gelatin-containing Aerosol-OT (AOT) microemulsion-based organogels (MBGs). The behavior of this novel, predominantly hydrophobic matrix as an esterification catalyst has been examined. The biocatalyst was most effective when the MBG was granulated to yield gel particles of ∼500 μm diameter, providing a total surface area of ca. 106 mm2 per 10 cm3 of gel. The gel was generally contacted with a solution of the substrate(s) in a hydrocarbon oil. Under most conditions reaction was not diffusion limited. Apparent lipase activity was influenced by certain compositional changes in the MBG, but most significantly when the R value, the mole ratio of water to surfactant, was altered. Higher activities were observed at lower R values. Although gels of lowest R value expressed the highest condensation activity, such formulations were physically unsuitable as immobilization matrices due to their proximity to the gel-solution phase boundary. MBGs of intermediate R values (between 60 and 80) were considered most suitable because they offer relatively high condensation activity and good physical stability. The gelatin concentration also exerted a small but measurable influence on the observed condensation rates. Apparent lipase activity was also influenced to some extent by the nature of the parent hydrocarbon used to prepare the MBG. Higher activities were obtained using formulations derived from isooctane and cyclohexane rather than the n-alkanes. Condensation activities expressed by CV lipase in the MBGs were broadly comparable to those expressed in the analogous parent water-in-oil (w/o) microemulsions. The MBGs functioned effectively in neat substrate solutions, but the condensation activity expressed by the MBGs in a series of successive batch syntheses was adversely affected by the formation and retention of the water coproduct. Selective removal of the water was achieved using a concentrated solution of dry reverse micelles, which resulted in recovery of lost activity. Pretreatment of lipase-containing MBGs resulted in the formation of MBGs with enhanced catalytic properties and modified composing the conventional procedure. © 1997 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    On-line monitoring and control of methanol concentration in shake-flask cultures of Pichia pastoris (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 279-286 
    Details
    ISSN: 0006-3592
    Schlagwort(e): methanol sensor ; methanol monitoring and control ; methylotrophic yeast fermentation ; Pichia pastoris ; transferrin ; shake-flask cultures ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The methylotrophic yeast Pichia pastoris can be used to express recombinant genes at high levels under the control of the methanol-inducible alcohol oxidase 1 (AOX1) promoter. Accurate regulation of the methanol concentration in P. pastoris cultures is necessary to maintain induction, while preventing accumulation of methanol to cytotoxic levels. We developed an inexpensive methanol sensor that uses a gas-permeable silicone rubber tube immersed in the culture medium and an organic solvent vapor detector. The sensor was used to monitor methanol concentration continuously throughout a fed-batch shake-flask culture of a P. pastoris clone producing the N-lobe of human transferrin. The sensor calibration was stable for the duration of the culture and the output signal accurately reflected the methanol concentration determined off-line by HPLC. A closed-loop control system utilizing this sensor was developed and used to maintain a 0.3% (v/v) methanol concentration in the culture. Use of this system resulted in a fivefold increase in volumetric protein productivity over levels obtained using the conventional fed-batch protocol. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 279-286, 1997.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Double inhibition model for degradation of phenol by Pseudomonas putida Q5 (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 560-567 
    Details
    ISSN: 0006-3592
    Schlagwort(e): phenol degradation ; Pseudomonas putida ; inhibition model ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A semiempirical model, based on the presence of an inhibitory intermediate metabolite excreted to the broth, was developed to better predict the dynamic responses to shock loadings of Pseudomonas putida Q5 degrading phenol. Compared to the Haldane equation, the new model exhibited better prediction capabilities for a broad range of inlet concentration and dilution rate step changes. The experiments were performed at 10° and 25°C and ranged from stable responses to washouts. The time delays observed experimentally were successfully predicted with the dual-inhibition model and a very good agreement with the observed phenol profile also was found in a pulse experiment. A possible intermediate metabolite was detected by HPLC analyses based on the high correlation shown with the predicted inhibitory intermediate metabolite in the model. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 560-567, 1998.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Oxygen absorption in stirred tanks: A correlation for ionic strength effects (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 755-782 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new correlation is given for the prediction of the volumetric coefficient for mass transfer (KLa) in stirred tanks from dispersed gas bubbles to basal salt solutions of ionic strengths representative of fermentation media. The correlation includes the effects of both the operating parameters (agitation power per unit volume and gas superficial velocity) and the physicochemical properties of the system: interfacial tension, viscosity, density, diffusion, coefficient and, in particular, ionic strength. The effect of the latter was found to be most significant in the Newtonian systems of water-like viscosity investigated; no previous correlations have included the effect of ionic strength. KLa values were determined by using a dissolved oxygen probe to monitor the steady-state oxygen tension in continuous flow experiments, and/or the rate of change of oxygen tension in unsteady-state semibatch experiments. In the latter cases, results were computed by a nonlinear, least squares computer program which fitted the experimental data to a model of probe transient response characteristics. The general applicability of the model and the computational procedure was verified by comparing the results to those obtained with the same electrolyte solution in the steady-state mode. The experiments were run over a wide range of agitation power inputs, including those typical of both soluble- and insoluble-substrate fermentations. The correlation appears to be valid for both oxygen mass transfer with and without homogeneous chemical reaction in the liquid phase; in the former case, for example, sulfite oxidation, knowledge of the chemical reaction enhancement factor is required. In addition to predicting oxygen transfer capabilities, the correlation may be used for other sparingly soluble gases of interest in fermentation systems, such as methane, hydrogen, and carbon dioxide.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260150409
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  • 5
    Digitale Medien
    Digitale Medien
    Pulp and paper mill solid wastes as substrates for single-cell protein production (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 561-573 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We have investigated the upgrading of some typical pulp and paper mill solid wastes into protein-enriched animal feed using the cellulolytic fungus Chaetomium cellulolyticum. The waste residues used were six different primary clarifier sludges and a sample of tertiary centricleaner rejects. These were obtained from mills whose modes of operation spanned the range typically in present-day usage: groundwood, sulfite, semichemical, Kraft, and thermomechanical pulping, with and without bleaching. Crude protein production from the solid waste residues is compared to that obtainable from fermentation of untreated or caustic-pretreated sawdusts. Some of these waste residues, especially the Kraft pulp mill rejects, appear to be promising sources of substrate for single-cell protein production. In these preliminary findings, up to 28% dry weight crude protein content of the product has been obtained at specific growth rates of up to 0.12hr-1 on direct utilization of the wastes.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260210404
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  • 6
    Digitale Medien
    Digitale Medien
    SCP production by Chaetomium cellulolyticum, a new thermotolerant cellulolytic fungus (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 527-538 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Chaetomium cellulolyticum, a newly isolated cellulolytic fungus, showed 50-100% faster growth rates and over 80% more final biomass-protein formation than Trichoderma viride, a well-known high cellulase-producing cellulolytic organism, when cultivated on Solka-floc (a purified, predominantly amorphorous form of cellulose) or partially delignified sawdust (consisting of a mixture of hardwoods) as the sole-carbon source in the fermentation media. However, in both cases, T. viride produced much higher quantities of free cellulases at faster rates and also degraded more substrate than C. cellulolyticum. It is concluded that the synthesis mechanisms and/or the nature of the cellulase complexes of the two types of organisms are quite different such that C. cellulolyticum is more optimal for single-cell protein (SCP) production, while T. viride is more optimal for the production of extracellular cellulases.It was also found that the amino acid composition of C. cellulolyticum is generally better than that of T. viride and compares favorably with those of the FAO reference protein, alfalfa, and soya meal. In addition, preliminary feeding trials on rats have shown no adverse effects of the SCP produced by C. cellulolyticum fermentations.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260190407
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  • 7
    Digitale Medien
    Digitale Medien
    Oxygen transfer in mechanically agitated aqueous systems containing dispersed hydrocarbon (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 661-682 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effect of dispersed n -dodecane or n -hexadecane on the air-to-aqueous phase overall volumetric oxygen transfer coefficient in a simulated (cell-free) stirred-tank fermentor is described. The oil volume fraction ranged from zero to 0.10; the ionic strength of the aqueous phases was varied from 0 to 0.45. The air-to-aqueous phase coefficients in both oil-free (KLa) and oil-bearing (KLa*) systems were evaluated from unsteady-state experiments using a membrane-covered probe to follow the aqueous phase dissolved oxygen tension.For all systems studied, KLa*/KLa was found to be independent of P/V and vs for all practical purposes. However, for a particular aqueous phase and at a given P/V and vs, the ratio KLa*KLa generally differed from unity. Depending on the combination of hydrocarbon type and volume fraction and the aqueous-phase ionic strength employed, the dispersed hydrocarbon may, in some cases, reduce the rate of oxygen transfer and in others enhance it relative to that of the corresponding oil-free gas-liquid dispersion. Enhancement of the air-to-aqueous transfer rate by such negative spreading coefficient hydrocarbons has not been reported previously.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260190505
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  • 8
    Digitale Medien
    Digitale Medien
    Improved method for the dynamic measurement of mass transfer coefficient for application to solid-substrate fermentation (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 23 (1981), S. 1611-1622 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A new method has been developed for the measurement of overall volumetric mass transfer coefficient (KLa) in gas-liquid-solid systems. This method is based on the examination of gas phase dynamics in a three-phase contactor and consists of measuring continuously the response of the outlet gas composition to a step input change of CO2 in the inlet gas stream. The advantages and limitations of the new method are presented and its sensitivity is discussed on the basis of model predictions. Preliminary results on the implementation of the CO2 method are also reported. Experimental data obtained in a nonviscous electrolyte solution show that the proposed method compares favorably with the conventional dissolved oxygen technique, provided that a correction is made to take account of the difference in diffusivity of oxygen and carbon dioxide.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260230718
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  • 9
    Digitale Medien
    Digitale Medien
    Microbial oxidation of dibenzothiophene by the thermophilic organism Sulfolobus acidocaldarius (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 687-690 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The refractory organic sulfur compound dibenzothiophene (DBT) has been oxidized by the thermophilic, sulfur oxidizing organism Sulfolobus acidocaldarius. Sulfate ions were released into the medium as the oxidation product. The kinetics of this oxidation have been investigated on the basis of sulfate released as a result of oxidation. Dibenzothiophene was found to be inhibitory to the organisms for initial concentrations over 500 mg/L. The organism may prove to be capable of oxidizing thiophene compounds present in oil refinery wastewater, coal, and crude oil.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260260709
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  • 10
    Digitale Medien
    Digitale Medien
    Evaluation of organosolv processes for the fractionation and modification of corn stover for bioconversion (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 572-581 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Corn stover was pretreated for compositional fractionation and structural modification for maximum conversion of carbohydrate to soluble sugars. The process scheme consisted of three steps: (1) mild prehydrolysis in dilute sulfuric acid, (2) delignification with various organosolv solvents, and (3) enzymatic hydrolysis in an agitated bead reactor. Prehydrolysis of corn stover can be achieved at temperatures ranging from 95 to 120°C, which is a much milder condition than must be applied to wood. Various organosolv solvents, including several alcohols with acid as catalyst, ethylene glycol, and its derivatives, and amines were used for delignification of the prehydrolyzed corn stover. Aromatic alcohols were found to be more effective in solubilizing the prehydrolyzed corn stover than were the aliphatic alcohols. Butanol was the most effective among the aliphatic alcohols; on the other hand, phenol was the best among the aromatic alcohols. Ethylene glycol, methylcellosolv, and ethylcellosolv were effective in solubilizing the prehydrolyzed corn stover but not for enhancing the enzymatic hydrolysis. Various amines achieved delignification at the mild temperature of 95°C, but they tended to solubilize substantial amounts of carbohydrate in addition to lignin. n-Butylamine was effective in enhancing the conversion during enzymatic hydrolysis; it was a good delignifying agent as well as one that achieved a concomitant swelling of the cellulose structure. The low enzymic conversion (20-37%) of prehydrolyzed and solvent-extracted corn stover that was achieved implies that lignin is not the only major barrier for enzymatic hydrolysis. Modification of cellulose structure also should be accomplished to achieve a high degree of conversion. Enzymatic hydrolysis in the agitated bead system increased the rate and extent of conversion of corn stover substantially compared to systems without beads.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260290506
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