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  • Biochemistry and Biotechnology  (13.095)
  • AERODYNAMICS  (12.790)
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  • 11
    Digitale Medien
    Digitale Medien
    Generating controlled reducing environments in aerobic recombinant Escherichia coli fermentations: Effects on cell growth, oxygen uptake, heat shock protein expression, and in vivo CAT activity (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 248-259 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Escherichia coli ; Chloramphenicol Acetyltransferase (CAT) ; Culture Redox Potential (CRP) ; Dithiothreitol (DTT) ; reducing agents ; molecular chaperones ; proteases ; heat shock ; stress response ; protein folding ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The independent control of culture redox potential (CRP) by the regulated addition of a reducing agent, dithiothreitol (DTT) was demonstrated in aerated recombinant Escherichia coli fermentations. Moderate levels of DTT addition resulted in minimal changes to specific oxygen uptake, growth rate, and dissolved oxygen. Excessive levels of DTT addition were toxic to the cells resulting in cessation of growth. Chloramphenicol acetyltransferase (CAT) activity (nmoles/μg total protein min.) decreased in batch fermentation experiments with respect to increasing levels of DTT addition. To further investigate the mechanisms affecting CAT activity, experiments were performed to assay heat shock protein expression and specific CAT activity (nmoles/μg CAT min.). Expression of such molecular chaperones as GroEL and DnaK were found to increase after addition of DTT. Additionally, sigma factor 32 (σ32) and several proteases were seen to increase dramatically during addition of DTT. Specific CAT activity (nmoles/μg CAT min.) varied greatly as DTT was added, however, a minimum in activity was found at the highest level of DTT addition in E. coli strains RR1 [pBR329] and JM105 [pROEX-CAT]. In conjunction, cellular stress was found to reach a maximum at the same levels of DTT. Although DTT addition has the potential for directly affecting intracellular protein folding, the effects felt from the increased stress within the cell are likely the dominant effector. That the effects of DTT were measured within the cytoplasm of the cell suggests that the periplasmic redox potential was also altered. The changes in specific CAT activity, molecular chaperones, and other heat shock proteins, in the presence of minimal growth rate and oxygen uptake alterations, suggest that the ex vivo control of redox potential provides a new process for affecting the yield and conformation of heterologous proteins in aerated E. coli fermentations. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 248-259, 1998.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 12
    Digitale Medien
    Digitale Medien
    A review of experimental measurements of effective diffusive permeabilities and effective diffusion coefficients in biofilms (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 261-272 
    Details
    ISSN: 0006-3592
    Schlagwort(e): effective diffusive permeability ; diffusion coefficient ; biofilm ; cell density ; review ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Experimental measurements of effective diffusive permeabilities and effective diffusion coefficients in biofilms are reviewed. Effective diffusive permeabilities, the parameter appropriate to the analysis of reaction-diffusion interactions, depend on solute type and biofilm density. Three categories of solute physical chemistry with distinct diffusive properties were distinguished by the present analysis. In order of descending mean relative effective diffusive permeability (De/Daq) these were inorganic anions or cations (0.56), nonpolar solutes with molecular weights of 44 or less (0.43), and organic solutes of molecular weight greater than 44 (0.29). Effective diffusive permeabilities decrease sharply with increasing biomass volume fraction suggesting a serial resistance model of diffusion in biofilms as proposed by Hinson and Kocher (1996). A conceptual model of biofilm structure is proposed in which each cell is surrounded by a restricted permeability envelope. Effective diffusion coefficients, which are appropriate to the analysis of transient penetration of nonreactive solutes, are generally similar to effective diffusive permeabilities in biofilms of similar composition. In three studies that examine diffusion of very large molecular weight solutes ( 〉 5000) in biofilms, the average ratio of the relative effective diffusion coefficient of the large solute to the relative effective diffusion coefficient of either sucrose or fluorescein was 0.64, 0.61, and 0.36. It is proposed that large solutes are effectively excluded from microbial cells, that small solutes partition into and diffuse within cells, and that ionic solutes are excluded from cells but exhibit increased diffusive permeability (but decreased effective diffusion coefficients) due to sorption to the biofilm matrix. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:261-272, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 13
    Digitale Medien
    Digitale Medien
    II. Electrostatic effect in the aggregation of heat-denatured RNase A and implications for protein additive design (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 281-285 
    Details
    ISSN: 0006-3592
    Schlagwort(e): protein aggregation ; RNase A ; protein formulation ; protein additives ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the previous study (part I), heat-denatured RNase A aggregation was shown to depend on the solution pH. Interestingly, at pH 3.0, the protein did not aggregate even when exposed to 75°C for 24 h. In this study, electrostatic repulsion was shown to be responsible for the absence of aggregates at that pH. While RNase A aggregation was prevented at the extremely acidic pH, this is not an environment conducive to maintaining protein function in general. Therefore, attempts were made to confer electrostatic repulsion near neutral pH. In this study, heat-denatured RNase A was mixed with charged polymers at pH 7.8 in an attempt to provide the protein with excess surface cations or anions. At 75°C, SDS and dextran sulfate were successful in preventing RNase A aggregation, whereas their cationic, nonionic, and zwitterionic analogs did not do so. We believe that the SO3- groups present in both additives transformed the protein into polyanionic species, and this may have provided a sufficient level of electrostatic repulsion at pH 7.8 and 75°C to prevent aggregation from proceeding. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:281-285, 1998.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 14
    Digitale Medien
    Digitale Medien
    An experimental and modeling study on the removal of mono-chlorobenzene vapor in biotrickling filters (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 328-343 
    Details
    ISSN: 0006-3592
    Schlagwort(e): biotrickling filters ; biotrickling filter modeling ; mono-chlorobenzene ; biodegradation kinetics of mono-chlorobenzene ; chlorinated VOC emissions ; biofiltration ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Removal of mono-chlorobenzene (m-CB) vapor from airstreams was studied in a biotrickling filter (BTF) operating under counter-current flow of the air and liquid streams. Experiments were performed under various values of inlet m-CB concentration, air and/or liquid volumetric flow rates, and pH of the recirculating liquid. Conversion of m-CB was never below 70% and at low concentrations exceeded 90%. A maximum removal rate of about 60 gm-3-reactor h-1 was observed. Conversion of m-CB was found to increase as the values of liquid and air flow rate increase and decrease, respectively. The effects of pH and frequency of medium replenishment on BTF performance were also investigated. The process was successfully described with a detailed mathematical model, which accounts for mass transfer and kinetic effects based on m-CB and oxygen availability. Solution of the model equations yielded m-CB and oxygen concentration profiles in all three phases (airstream, liquid, biofilm). It is predicted that oxygen has a controling effect on the process at high inlet m-CB concentrations. From independent, suspended culture, experiments it was found that m-CB biodegradation follows Andrews inhibitory kinetics. The kinetic constants were found to remain practically unchanged after the culture was used in BTF experiments for 8 months. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:328-343, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    Digitale Medien
    Digitale Medien
    Effect of some operating variables on citrate recovery from model solutions by electrodialysis (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 344-350 
    Details
    ISSN: 0006-3592
    Schlagwort(e): electrodialysis ; citric acid ; pH ; temperature ; Faraday efficiency ; solute recovery efficiency ; specific energy consumption ; solute flux ; water flux ; feed solute concentration ; electric current density ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effect of pH and temperature (θ) on the overall performance indicators (i.e., solute recovery, ρ, and Faraday, η, efficiencies; specific energy consumption, ε, solute, JS, and water, JW, fluxes) of batch electrodialytic recovery of citric acid from model solutions was assessed at different values of feed solute concentration (cSf) and electric current density (j). Regardless of the initial feed concentration used, ρ and JS were found to be independent of θ; η and JW exhibited a positive trend with respect to θ, while ε a negative one. At the maximum temperature tested (33°C), as the pH of the feed solution was varied from 3 to 7, ρ increased from 0.90 ± 0.08 to 0.97 ± 0.02, η grew from 0.09 ± 0.02 to 0.50 ± 0.01, JS practically doubled, ε reduced about 8 times, but JW increased from 3 to 4 times. So, the optimal conditions for this technique are to be determined by balancing the savings in the investment and maintenance costs against the energy costs. © John Wiley & Sons, Inc. Biotechnol Bioeng 59:344-350, 1998.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Stability and activity modulation of chymotrypsins in AOT reversed micelles by protein-interface interaction: Interaction of α-chymotrypsin with a negative interface leads to a cooperative breakage of a salt bridge that keeps the catalytic active conformation (Ile16-Asp194) (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 360-363 
    Details
    ISSN: 0006-3592
    Schlagwort(e): chymotrypsin ; enzyme stability ; reversed micelles ; interface ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The stability of α-chymotrypsin and δ-chymotrypsin was studied in reversed micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in isooctane. α-Chymotrypsin is inactivated at the interface and at the water pool, while δ-chymotrypsin is inactivated only at the water pool. The mechanism of inactivation at the interface is related to the interaction of N-terminal group alanine 149 (absent in δ-chymotrypsin) with the negative interface. The dependence of enzyme activity on water content of these two enzymes in reversed micelles of AOT is also related with the interface interaction, since δ-chymotrypsin does not have a bell-shaped curve as observed for α-chymotrypsin. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:360-363, 1998.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    High-density perfusion culture of insect cells with a BioSep ultrasonic filter (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 351-359 
    Details
    ISSN: 0006-3592
    Schlagwort(e): bioreactor ; high density ; insect cells ; perfusion ; Sf9 ; ultrasonic filter ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The baculovirus/insect cell expression system has provided a vital tool to produce a high level of active proteins for many applications. We have developed a very high-density insect cell perfusion process with an ultrasonic filter as a cell retention device. The separation efficiency of the filter was studied under various operating conditions. A cell density of over 30 million cells/mL was achieved in a controlled perfusion bioreactor and cell viability remained greater than 90%. Sf9 cells from a high-density culture and a spinner culture were infected with two recombinant baculoviruses expressing genes for the production of human chitinase and monocyte-colony inhibition factor. The protein yield on a cell basis from infecting high-density Sf9 cells was the same as or higher than that from the spinner Sf9 culture. Virus production from the high-density culture was similar to that from the spinner culture. The results show that the ultrasonic filter did not affect insect cells' ability to support protein expression and virus production following infection with baculovirus. The potential applications of the high-density perfusion culture for large-scale protein expression from Sf9 cells are also highlighted. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:351-359, 1998.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 18
    Digitale Medien
    Digitale Medien
    Prevention of marine biofouling using a conductive paint electrode (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 374-378 
    Details
    ISSN: 0006-3592
    Schlagwort(e): conductive paint electrode ; prevention of marine biofouling ; fishing net ; alternating potential ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Conductive paint electrode was used for marine biofouling on fishing nets by electrochemical disinfection. When a potential of 1.2 V vs. a saturated calomel electrode (SCE) was applied to the conductive paint electrode, Vibrio alginolyticus cells attached on the electrode were completely killed. By applying a negative potential, the attached cells were removed from the surface of the electrode. Changes in pH and chlorine concentration were not observed at potentials in the range -0.6 ∼1.2 V vs. SCE. In a field experiment, accumulation of the bacterial cells and formation of biofilms on the electrode were prevented by application of an alternating potential, and 94% of attachment of the biofouling organisms was inhibited electrically on yarn used for fishing net coated with conductive paint. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:374-378, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Mass transfer studies on immobilized α-chymotrypsin biocatalysts prepared by deposition for use in organic medium (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 364-373 
    Details
    ISSN: 0006-3592
    Schlagwort(e): porous supports ; internal and external diffusion ; active site accessibility ; enzyme loading ; kinetically controlled dipeptide synthesis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Mass transfer limitations were studied in enzyme preparations of α-chymotrypsin made by deposition on different porous support materials such as controlled pore glasses, Celite, and polyamides of different particle sizes. It is the onset of mass transfer limitations that determines the position of the activity optimum with respect to enzyme loading on each support. The evidence of various experiments indicates that internal diffusional limitations are the important mechanism for the observed mass transfer limitations. External diffusion was not found to play an important role under the conditions used, and it was also found that when immobilizing multilayers of enzyme the buried enzyme molecules are active to a large extent. An extreme situation is observed on Celite at very high loadings. Under these conditions, this support is expected to have its pores completely filled with packed enzyme molecules, and then it is the diffusion within the enzyme layer that determines the observed rate. As the enzyme loading increases, the area of contact between the deposited enzyme layers and the liquid solution inside the pores diminishes, causing a decrease on the observed rate of an intrinsically fast reaction which apparently is incongruous with the presence of more enzyme in the system. This work shows that mass transfer limitations can be an important factor when working with immobilized enzymes in organic media, and its study should be carried out in order to avoid undesired reduced enzyme activities and specificities. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:364-373, 1998.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 20
    Digitale Medien
    Digitale Medien
    Degradation of perchloroethylene and dichlorophenol by pulsed-electric discharge and bioremediation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 438-444 
    Details
    ISSN: 0006-3592
    Schlagwort(e): bioremediation ; plasma discharge ; dichlorophenol degradation ; perchloroethylene degradation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Pulsed electric discharge (PED) and bioremediation were combined to create a novel two-stage system which dechlorinates the halogenated pollutants, 2,4-dichlorophenol and perchloroethylene, with repetitive (0.1-1 kHz), short pulse (∼100 ns), low voltage (40-80 kV) discharges and then mineralizes the less chlorinated products with aerobic bacteria. A 6.1 mM aqueous dichlorophenol sample was cycled through the PED reactor (60 kV of applied pulsed voltage and 300 Hz) 6 times, resulting in the release of 55% of the initial dichlorophenol chloride ions (1 mM Cl- removed each cycle). The respective average specific efficiency is 0.4-0.6 keV/(Cl- molecule). Pseudomonas mendocina KR1, which grows in minimal medium supplemented with phenol but not with dichlorophenol, increased in cell density in all cultures supplemented with the PED-treated DCP samples and yielded a maximum of two-fold additional Cl- released compared to the PED-related alone. The number of PED-treatment cycles, voltage, and frequency were also varied, showing that both cell densities and overall dichlorophenol dechlorination were highly dependent upon the number of PED-treatment cycles, rather than the tested voltages and frequencies. Using this two-stage treatment system, PED released 31% of the initial chloride ions from dichlorophenol (after three cycles at 40-45 kV and 1.2 kHz) while P. mendocina KR1 in the second stage increased dechlorination to 90%. These results were corroborated by the 35% additional chloride release found with activated sludge cultures. Perchloroethylene (0.6 mM) was similarly treated in a first-stage PED reactor (80% chloride removal after four cycles) followed by biodegradation of the dechlorinated products with a recombinant toluene o-monooxygenase-expressing Pseudomonas fluorescens strain. Gas chromatographic analysis showed that the PED reactor created less-chlorinated byproducts (i.e., trichloroethylene) that were removed (74%) upon exposure to the recombinant bacterium. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:438-444, 1998.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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