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  • Biochemistry and Biotechnology  (13,095)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 127-135 
    ISSN: 0006-3592
    Keywords: membrane mass spectrometer ; kinetic measurements ; anaerobic biofilm ; acetate ; inhibition ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A small, stirred, 14.4-mL tank reactor was designed to serve as a measurement cell for short-term investigation of microbial kinetics. A mass spectrometer membrane probe allowed the measurement of the dissolved gases of hydrogen, methane, oxygen, and carbon dioxide. pH was measured by an electrode and controlled by addition of acid or alkali. The highly sensitive measurement of gases with low solubility allowed rapid measurements at very low conversion. In kinetic experiments, a stepwise increase of substrate concentration (method A) and continuous feed of substrate (method B) were used, allowing quick estimation of substrate kinetics. Acetate conversion in mixed culture biofilms from a fluidized bed reactor was investigated. Substrate inhibition was found to be negligible in the concentration range studied. Experiments at various pH values showed that the undissociated acid form was the kinetic determinant. Kinetic parameters for Haldane kinetics of protons were KSH = 1.3 × 10-5 mol m-3 and KIH = 8.1 × 10-3 mol m-3. With free acid (HAc) as the rate determining species, the kinetic parameters for method A were KSHAc = 0.005 mol m-3 and KIHAc = 100 mol m-3 and for method B were KSHAc = 0.2 mol m-3 and KIHAc = 50 mol m-3. The maximum biomass activity occurred at around pH 6.5. Acetate was exclusively converted to methane and CO2 at pH 〉 6. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 127-135, 1998.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 187-197 
    ISSN: 0006-3592
    Keywords: algal cultures ; photosynthetic efficiency ; light saturation effect ; spatial dilution of light ; Arthrospira (Spirulina) platensis ; tubular and flat photobioreactors ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The light saturation effect imposes a serious limitation on the efficiency with which solar energy can be utilized in outdoor algal cultures. One solution proposed to reduce the intensity of incident solar radiation and overcome the light saturation effect is “spatial dilution of light” (i.e., distribution of the impinging photon flux on a greater photosynthetic surface area), but consistent experimental data supporting a significant positive influence of spatial light dilution on the productivity and the photosynthetic efficiency of outdoor algal cultures have never been reported. We used a coiled tubular reactor and compared a near-horizontal straight tubular reactor and a near-horizontal flat panel in outdoor cultivation of the cyanobacterium Arthrospira (Spirulina) platensis under defined operating conditions for optimum productivity. The photosynthetic efficiency achieved in the tubular systems was significantly higher because their curved surface “diluted” the impinging solar radiation and thus reduced the light saturation effect. This interpretation was supported by the results of experiments carried out in the laboratory under continuous artificial illumination using both a flat and a curved chamber reactor. The study also showed that, when the effect of light saturation is eliminated or reduced, productivity and solar irradiance are linearly correlated even at very high diurnal irradiance values, and supported findings that outdoor algal cultures are light-limited even during bright summer days. It was also observed that, besides improving the photosynthetic efficiency of the culture, spatial dilution of light also leads to higher growth rates and lowers the cellular content of accessory pigments; that is, it reduces mutual shading in the culture. The inadequacy of using volumetric productivity as the sole criterion for comparing reactors of different surface-to-volume ratio and of the areal productivity for evaluating the performance of elevated photobioreactors operated outdoors is stressed; it is furthermore suggested that the photosynthetic efficiency achieved by the culture also be calculated to provide a suitable parameter for comparison of different algal cultivation systems operated under similar climatic conditions. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 187-197, 1998.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 211-215 
    ISSN: 0006-3592
    Keywords: protein ; conformational memory ; organic solvent ; molecular imprinting ; enzyme ; catalysis ; transition state analogue ; bovine serum albumin ; β-lactoglobulin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The induction of catalytic activity in proteins by lyophilization in the presence of a transition state analogue (biomolecular imprinting) has been attempted. It was shown that proteins which were freeze-dried with n-isopropyl-4-nitrobenzyl-amine (a transition state analogue for the reaction of dehydrofluorination of 4-fluoro-4-[p-nitrophenyl] butan-2-one) displayed higher β-elimination activity as compared to their-non-imprinted counterparts. It was also found that native bovine serum albumin has a high dehydrofluorination activity towards the above substrate with kinetic parameters rather similar to those of a catalytic antibody prepared by Shokat et al. (1989). A comparison of the kinetic parameters determined in this study with those obtained for analogous catalytic antibodies and imprinted polymers was made. © 1998 John Wiley & Sons, Inc. Biotechnol. Bioeng. 57: 211-215, 1998.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 62-70 
    ISSN: 0006-3592
    Keywords: plasmid stability ; recombinant microorganism ; continuous culture ; Pseudomonas sp. B13 FR1 pFRC20P ; degradation of aromatic compounds ; chlorobenzoate ; methylbenzoate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plasmid stability of recombinant Pseudomonas sp. B13 FR1 pFRC20P, a strain capable of mineralizing 3- and 4-chlorobenzoate and 4-methylbenzoate, was investigated in continuous culture. The hybrid cosmid pFRC20P enables the strain to mineralize 4-methylbenzoate. Rapid plasmid loss was observed under nonselective conditions using 3-chlorobenzoate as the substrate. Plasmid stability decreased with increasing dilution rate. Despite the growth advantage of the generated plasmid free cells a total depletion of plasmid bearing cells was not observed. After approximately 50 generations the fraction of plasmid bearing cells reached a constant level of 10%, which was stably maintained during the next 25 generations. Cells from this stage were used to inoculate a new culture that resulted in a stable level of 50% plasmid bearing cells. By a temporary substrate change to selective conditions (4-methylbenzoate), this level could be further increased to 70%. Literature models on plasmid stability could not be applied to describe the experimental data. Therefore, a new but unstructured model was developed to describe the experimental results. The model is based on the existence of three subpopulations: a plasmid free one, an original plasmid bearing one with a growth disadvantage compared to plasmid free cells, and a second plasmid bearing subpopulation with increased stability that is generated from the original one and has a growth rate comparable to the plasmid free cells. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 62-70, 1998.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 79-86 
    ISSN: 0006-3592
    Keywords: Alcaligenes eutrophus ; hydrogenase ; NADH regeneration ; HLADH ; organic solvent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A soluble NAD-dependent hydrogenase contained in Alcaligenes eutrophus was evaluated as a coenzyme regenerating catalyst in an organic-aqueous two-phase (predominantly organic) system. The horse-liver alcohol-dehydrogenase (HLADH) catalyzed reduction of cyclohexanone to cyclohexanol was used as a model reaction. The impact of different solvents (selected to span a large variety of principal properties) on the stability and activity of the HLADH, using substrate-driven regeneration, was studied. Solvents suitable for the HLADH were then selected for an evaluation of the hydrogenase-driven coenzyme regeneration. Hydrophobic solvents such as heptane, toluene, and 1,1,1-trichloroethane were found to be suitable for the coupled reactions catalyzed by HLADH and hydrogenase. Nonimmobilized cells, permeabilized with cetyl-trimethyl-ammonium bromide, were the most efficient preparation for the regeneration of NADH. The use of this preparation in heptane (10% water) was optimized with respect to the yield obtained in the HLADH-catalyzed reduction of cyclohexanone. Using the optimized conditions, yields of 99% cyclohexanol were obtained. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 79-86, 1988.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 95-108 
    ISSN: 0006-3592
    Keywords: Xanthan fermentation ; impeller type ; power consumption ; mixing ; oxygen transfer ; Xanthan productivity ; product quality ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The rheological complexity of Xanthan fermentations presents an interesting problem from a mixing viewpoint, because the phenomena of poor bulk blending and low oxygen mass transfer rates inherent in highly viscous fermentations (and their consequences) can be systematically investigated, even at the pilot plant scale. This study in a 150 L fermentor compares the physical and biological performance of four pairs of impellers: a standard Rushton turbine, a large diameter Rushton turbine, a Prochem Maxflo T, and a Scaba 6SRGT. Accurate in-fermentor power measurements, essential for the comparison of impellers in relation to operating costs are also reported. It is demonstrated that the agitator performance in Xanthan fermentations is very specific and the choice of which impeller to use in bioreactors to obtain enhanced performance is dependant on the applied criterion. None of the criterion favored the use of the standard Rushton turbine, therefore suggesting that there are strong grounds for retrofitting these impellers with either large diameter impellers of similar design or with novel agitators. In addition, fluid dynamic modeling of cavern formation has clearly highlighted the importance of a well mixed and oxygenated region for providing the capacity for high microbial oxygen uptake rates which govern Xanthan productivity and quality. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 95-108, 1998.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 121-125 
    ISSN: 0006-3592
    Keywords: sucrose monoester synthesis ; lipase-catalyzed acylation ; water activity (a w) ; regioselectivity ; salt hydrate pair ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sucrose monoesters of a fatty acid were synthesized by using lipase in a solvent-free system. When lipase from Mucor miehei was used as a catalyst with capric acid as the donor and sugar as the acceptor, sucrose 6-monocaprate was predominantly produced in a yield of 25.3%. The yield of product was significantly increased by the direct addition of a suitable pair of solid salt hydrates to the reaction mixture to control the water activity (aw). Among the salt hydrate pairs investigated, the barium hydroxide, 8/1H2O pair resulted in the highest yield of the product. This salt addition method was also successfully employed for acylation of primary hydroxyl groups in various unprotected mono- and disaccharides such as glucose, galactose, fructose, trehalose, mannose, maltose, and lactose. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 121-125, 1998.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 118-120 
    ISSN: 0006-3592
    Keywords: biocompatibility ; microfabrication ; biohybrid organs ; immunoisolation ; Islets of Langerhans ; silicon ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A microfabricated silicon-based biocapsule for the immunoisolation of cell transplants is presented. The biocapsule-forming process employs bulk micromachining to define cell-containing chambers within single crystalline silicon wafers. These chambers interface with the surrounding biological environment through polycrystalline silicon filter membranes. The membranes are surface micromachined to present a high density of uniform pores, thus affording sufficient permeability to oxygen, glucose, and insulin. The pore dimensions, as small as 20 nm, are designed to impede the passage of immune molecules and graft-borne viruses. The underlying filter-membrane nanotechnology has been successfully applied in controlled cell culture systems (Ferrari et al., 1995), and is under study for viral elimination in plasma fractionation protocols. Here we report the encouraging results of in vitro experiments investigating the biocompatibility of the microfabricated biocapsule, and demonstrate that encapsulated rat neonatal pancreatic islets significantly outlive and outperform controls in terms of insulin-secretion capability over periods of several weeks. These results appear to warrant further investigations on the potential of cell xenografts encapsulated within microfabricated, immunoisolating environments for the treatment of insulin-dependent diabetes. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 118-120, 1998.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 145-154 
    ISSN: 0006-3592
    Keywords: bioavailability ; PAH ; biodegradation ; dissolution ; hydrodynamic ; mixing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of hydrodynamic conditions on the dissolution rate of crystalline naphthalene as a model polycyclic aromatic hydrocarbon (PAH) was studied in stirred batch reactors with varying impeller speeds. Mass transfer from naphthalene melts of different surface areas to the aqueous phase was measured and results were modeled according to the film theory. Results were generalized using dimensionless numbers (Reynolds, Schmidt, and Sherwood). In combined mass transfer and biodegradation experiments, the effect of hydrodynamic conditions on the degradation rate of naphthalene by Pseudomonas 8909N was studied. Experimental results were mathematically described using mass-transfer and microbiological models. The experiments allowed determination of mass-transfer and microbiological parameters separately in a single run. The biomass formation rate under mass transfer limited conditions, which is related to the naphthalene biodegradation rate, was correlated to the dimensionless Reynolds number, indicating increased bioavailability at increased mixing in the reactor liquid. The methodology presented in which mass transfer processes are quantified under sterile conditions followed by a biodegradation experiment can also be adapted to more complex and realistic systems, such as particulate, suspended PAH solids or soils with intrapartically sorbed contaminants when the appropriate mass-transfer equations are incorporated. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 145-154, 1998.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 136-144 
    ISSN: 0006-3592
    Keywords: down-flow fluidization ; bed expansion ; biofilm ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article describes the bed expansion characteristics of a down-flow anaerobic fluidized bed reactor treating a synthetic wastewater. Experiments were carried out in a 0.08 m diameter and 1 m length PVC column. The carrier used was ground perlite (an expanded volcanic rock). Particles characteristics were 0.968 mm in diameter, specific density of 213 kg · m-3 and Umf (minimal fluidization velocity): 2.3 m · h-1. Experimental data of terminal velocities and bed expansion parameters at several biofilm thicknesses were compared to different models predicting the bed expansion of up-flow and down-flow fluidized beds.Measured bed porosities at different liquid superficial velocities for the different biofilm thicknesses were in agreement with the Richardson-Zaki model, when Ut (particle terminal velocity) and n (expansion coefficient) were calculated by linear regression of the experimental data. Terminal velocities of particles at different biofilm thicknesses calculated from experimental bed expansion data, were found to be much smaller than those obtained when Cd (drag coefficient) is determined from the standard drag curve (Lapple and Sheperd, 1940) or with others' correlations (Karamanev and Nikolov, 1992a,b). This difference could be explained by the fact that free-rising particles do not obey Newton's law for free-settling, as proposed by Karamanev and Nikolov (1992a,b) and Karamanev et al. (1996). In the present study, the same free-rising behavior was observed for all particles (densities between 213 and 490 kg · m-3). © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 136-144, 1998.
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