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  • 1
    ISSN: 0167-7799
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The aerobic microbial population of natural hot spring water was investigated by means of taxonomic analyses of 33 characteristic properties. Twenty-eight strains isolated in Iceland were compared with 3 Thermus and 4 Bacillus reference strains. The results showed a high variability in the characteristics of bacteria isolated from nearby sampling areas. No typical sampling-area-specific or temperature-specific populations were found. These findings suggested high diversity of thermophiles due to environmental factors. In this report adaptation mechanisms are postulated and discussed in relation to the growth behaviour of Thermus strains in the natural environment and in continuous cultivation.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Cells ofThermoanaerobium brockii were immobilized by entrapment methods as easy-to-handle biocatalyst for stereoselective reductions of oxo-acid esters. Different matrix materials were tested: agarose, k-carrageenan, alginate, polyacrylamide and polyurethanes. The two latter matrices allowed useful lifetimes of the immobilized biocatalysts of more than 2 months at thermophilic operation temperatures (around 65°C). Permeabilization of cells did not improve the catalytic activity. Immobilization of the cells did not enhance the thermostability. Only after a considerable period of operation could the immobilized biocatalysts be fed with medium lacking the complex substrates yeast extract and tryptone. Compared with freely suspended cells, reaction rates were lower. The immobilized system proved to be a relatively stable easy-to-handle biocatalyst, however, the freely suspended cells were superior with respect to flexibility of application and reaction velocity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The growth of the yellow pigmented non-sporulating caldoactive bacterium Thermus aquaticus was investigated in different culture vessels and using differnt culture techniques. Each combination of these two variables led to very specific characteristic behaviour of the culture. A synthetic medium for a white cell type of T. aquaticus was optimized by means of pulse and medium-shift techniques. The main kinetic parameters of the organism have been determined to be μ=1.62h−1 and Y (glucose)=0.4 g g−1 at T=68 °C and pH=7.3. In complex medium only a mixed population of white and yellow cells could be cultivated. The cell yield was shown to be very low (Y=0.02 g g−1) due to incomplete substrate utilisation, but a very high maximal specific growth rate was determined (μ max=3.5h−1) at 75 °C and pH=7.3. The maintenance coefficient for oxygen uptake was approximately Mo=16 mMol g−1 h−1. A discussion of the problems arising in the cultivation of thermophilic microorganisms with respect to their physiology and stability is given.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The gas chromatographic method for the determination of poly-β-hydroxybutyric acid (PHB) consists of a mild acid or alkaline methanolysis of poly-β-hydroxybutyric acid directly without previous extraction of PHB from the cells; this is followed by gas chromatography of the 3-hydroxybutyric acid methylester. The method is characterized by high accuracy and excellent reproducibility, permitting determinations as low as 10−5 g/l. Only 4 h is required from sampling from the fermenter till completion of the PHB determination.
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  • 6
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The nonsporulating extreme thermophile Thermus thermophilus was grown in continuous culture at dilution rates up to 2.65 h−1 at 75°C and pH 6.9 on complex medium. Concomitantly very low yield (Y=0.12 g cell dry weight g−1 utilized organic carbon) and incomplete substrate utilization (always less than 45%) were found. In batch cultures T. thermophilus could be grown with μ max =h−1, in shake flasks only with μ max =h−1 with the same low yield and incomplete substrate utilization. Stable steady states at 84δC and 45°C were realized at a dilution rate of 0.3 h−1 whereas at 86°C and 40°C no growth could be detected. Artefacts arising from wall growth (in bioreactors) or improper materials must be ruled out. Inhibition of growth by organic substrates was demonstrated at low concentrations: a decrease in the yield obtained was found when more than 0.7 gl−1 of meat extract were supplied in the medium. The maintenance requirement for oxygen is potentially very high and was determined to be 10 to 15 mmol g−1 h−1.
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  • 7
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Biomass production of Zymomonas mobilis in continuous cultivation on synthetic or complex glucose media was increased up to 100% when CO2 partial pressure was reduced from 1,460 to 95 mbar at high dilution rates. Biomass yield increased and specific glucose uptake and ethanol production rates decreased approximately 6% when pCO2 was lowered from 1,160 to 95 mbar. Product yield was not affected by pCO2. Long time adaptation superimposing these effects was considered.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Under chemolithoautotrophic growth conditions with the organism Alcaligenes eutrophus H16 the exponential growth phase is characterized by two different growth rates, each associated with different specific rates of ammonium consumption. On the basis of the analytical determination of Poly-β-hydroxybutyric acid (PHB), it can be conclusively shown that PHB is synthesized even during the exponential growth phase at a specific rate proportional to the specific growth rates of total biomass. After complete consumption of ammonium, the increase of biomass is exclusively due to PHB synthesis, whereas protein and rest biomass (cell dry weight minus PHB) remain constant. After an extended period of fermentation, the PHB content reaches a saturation value. The transient phase between the growth and the storage phase is very short in comparison to the duration of the whole fermentation. In the case of Alcaligenes eutrophus, strain H 16, high concentrations of dissolved oxygen strongly influence growth as well as PHB synthesis.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Bioprocess and biosystems engineering 6 (1991), S. 187-193 
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The dynamic behavior of yeasts is discussed on the basis of transient experiments, such as pulses and shifts in continuous culture, and of oscillating synchronized cultures. The minimal elements of a structured model are evaluated and extensions by regulatory mechanisms are proposed. Segregation of a population in cell classes reflecting the position of a cell in the cell cycle, its individual age, is shown to be necessary in order to account for the spontaneous synchronization of continuous S. cerevisisae cultures.
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  • 10
    ISSN: 1432-0797
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The introduced method of pattern recognition is a tool for on line control purposes. It is based on the detection of complex states of (bio-)technological processes. The process data are treated in a comprehensive way which allows the formulation and detection of interrelations between different signals. Not only single signals rather than a multiple set defines the state of a process (more) completely. This allows to perform “advanced control” of the “physiological state” of a population and additionally the on line supervision of the technical equipment. Differences in absolute values between corresponding states do not impair the inter-signal associations seriously if the general character of the trajectories remains unchanged. Hence, this approach is very similar to a human view of processes and is suited to serve in expert systems. First results are shown concerning stability of the recognition procedure and a practical approach is introduced performing the automatic detection of defective sensors.
    Type of Medium: Electronic Resource
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