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  • 1
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Pellets of Penicillium chrysogenum which were spontaneously formed after a certain stage of a batch fermentation, displayed a considerable structural change in course of their lifetime. Microelectrode studies showed the internal mass transport properties of these pellets (diameter 1–3 mm) to be highly effected by their morphological structure. Relatively young pellets, in an early stage of the batch fermentation, possessed a homogeneous and dense structure. These pellets were only partly penetrated by oxygen (ca. 70 μm) at air saturated bulk conditions. Older pellets, in a final stage of the batch fermentation, were stratified and fluffy. They were completely penetrated by oxygen due to a decreased activity and a higher diffusivity. Investigations with glucose microelectrodes revealed that glucose consumption inside pellets of all lifetimes exclusively occurred in the periphery, indicating that growth was restricted to these regions only.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 11 (1994), S. 121-121 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Ethanol was produced with Zymomonas mobilis Z6 (ATCC 29191), in batch culture with synthetic medium on glucose as substrate and in the presence of aspartate. The concentrations of glucose, phosphate, ammonium, ethanol and dissolved O2 and CO2 in the medium and O2 and CO2 in the outlet gas as well as the cell mass by culture fluorescence were measured on-line. Cell mass, glucose and aspartate concentrations were measured off-line. In the presence of a sufficient amount of aspartate, the ethanol inhibition effect can be reduced considerably. However, the improvement with yeast extract is more incisive. The relationship between the intensity of culture fluorescence and cell mass concentration is linear, if sufficient aspartate is present.
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Spacial, mean and Sauter bubble diameters, local mean gas holdups and specific interfacial area profiles were evaluated in bench scale bubble column reactors with a model medium and during the cultivation of a yeast,Hansenula polymorpha, on ethanol and glucose substrates. The results indicate that the spacial variation of these properties in most of the column (with the exception of the aerator zone) is slight. These two-phase system can therefore be characterized by local values measured in the column. The variation in the mean and Sauter bubble diameters, the specific interfacial area, the volumetric mass transfer coefficient, the oxygen transfer rate and the biomass concentration were determined during cultivation as functions of time and substrate concentration. There is a close relationship between system properties measured in both model and cultivation media. However, during cultivation, small bubbles are formed which gradually accumulate in the medium. This causes a significant increase in the specific geometric interfacial area. A comparison of this area with the corresponding volumetric mass transfer coefficient indicates that only part of this area is active with regard to oxygen transfer. The active mass transfer area can be evaluated by disregarding small bubbles with diameters of less than 0.8 mm.
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary As part of a project on the production of penicillin, the penicillin production of two strains of Penicillium chrysogenum which have a different penicillin productivity was investigated in bubble column bioreactors and for comparison in stirred fermenters. The main interest of this study were the complicated interrelations between the stirrer speed, the stirrer type, the shear stress, the morphology of the mycelium and broth viscosity as well as the effect of the oxygen transfer behavior on antibiotic productivity. Stirred tank reactors with different turbine stirrers as well as with a draught tube and propeller were employed. The main variable investigated was the stirrer speed. At low stirrer speeds, gas dispersion is inadequate and the insufficient oxygen transfer rate is a limiting factor. At higher stirrer speeds, the oxygen supply of pulpy mycelia is improved and more cell mass is formed. This result is the same for both strains in all three reactors. If the oxygen partial pressure is near the lower cirtical value, a high percentage of the carbon source is converted into penicillin but the penicillin productivity is low due to a low percentage of penicillin producing cells. At oxygen partial pressures just above 8% saturation, the absolute penicillin productivity is maximal. At higher stirrer speeds and dissolved oxygen concentrations the penicillin production phase is shorter, cell growth is higher and a higher percentage of the carbon source is converted into CO2. In reactors with a draught tube and propeller, a lower productivity is attained than in those with turbine stirrers. The behavior of the two strains is fairly similar. The higher producing strain, however, has a more distinct separation between its periods of growth and production than does the low producing one. At high stirrer speeds the increase in the cell growth rate is less significant and the substrate yield coefficients are higher for the high producing strain than for the low producing one.
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  • 6
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Potato protein liquor (PPL)+glucose solutions were heat treated and sterilized in the absence and presence of an antifoam agent at temperatures between 80 and 120 °C for a period of 5.0 s to 30 min. The foaminess, Σ, of nonsterile and sterile solutions was measured at different aeration rates. The foaminess of PPL solutions was negligible before sterilization. After sterilization at 120 °C for 30 min the foaminess increased by a factor of more than 2·103. With decreasing temperature and duration of heat treatment, with decreasing pH and increasing antifoam concentration the foaminess of the sterilized PPL solution diminishes considerably. Foam formation is caused by protein denaturation and by the Maillard reactions.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 221-226 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Several antifoam agents were tested under standardized conditions with regard to their foam-reducing effect on BSA solutions. The surface tension of these systems was measured as well. There is no simple relationship between foaminess and surface tension in the systems employed in this case. According to these investigations polyethers are the most effective antifoam components. Of the silicone components organic polyether modified dimethyl polysiloxanes + silica seem to be most efficient.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 17 (1983), S. 314-318 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The proteins in the supernatant of Trichoderma reesei were separated by HPLC and exo-, endo-β 1,4-glucanase, and β-glucosidase activities for the various fractions obtained were measured. Bovine serum albumin (BSA), chymotrypsin, β-glucosidase, endoglucanase and other cellulase preparates were used as reference substrates.
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary To satisfy the demand for simple production technology (simple and cheap reactor, cheap recovery and finishing), solid state cultivations were carried out with pretreated straw in a simple fixed bed reactor under nonsterile conditions. The results of these investigations were compared with those evaluated in a stirred tank reactor. The same cell mass fractions were obtained in both reactors. However, about double the cultivation time is necessary for a solid state cultivation as compared to a submerse cultivation.
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  • 10
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Fluorometric measurements were performed in continuous aerobic cultures ofSaccharomyces cerevisiae in order to study the effect of substrate concentration and residence time on the intracellular NADH-level. A modified Beyelermicrofluorometer probe (Beyeler et al. 1981) was used for the experiments. It was possible to use this sensor continuously up to five weeks without problems. The relative NADH-values obtained by the on-line monitoring of the NADH-dependent culture fluorescence were compared to the enzymatically determined NADH-content. Biomass estimation from fluorescence data was performed. During oxidative-reductive catabolism the deviation between calculated and measured data were below 5%. The differences between oxidative and oxidative-reductive catabolism were studied regarding glucose addition, dilution rate increase and aerobic-anaerobic transition. For synchronized continuous cultures, changes in dilution rate resulted in changes of the oscillating behaviour. Flow cytometric studies in comparison with fluorometric studies showed changes in budding behaviour during the oscillations.
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