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  • 1980-1984  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 136 (1983), S. 203-208 
    ISSN: 1432-072X
    Schlagwort(e): Maximum growth yield ; Mixed substrate utilization ; Glucose ; Formate ; Transient-state cultivation ; Hansenula polymorpha
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The experimentally determined growth yield on glucose under aerobic conditions is approximately 0.5 g/g, but on the basis of the carbon content a value of 0.71 g/g should be the upper limit if carbon conversion is improved by the use of an additional energy source. This assumption was investigated with the methylotrophic yeast Hansenula polymorpha MH 20. Formate served as an additional energy source. The growth yield experiments were performed with a transient-state fermentation technique in which formate was fed via an increasing concentration gradient to a culture growing continuously on glucose. As a result the growth yield on glucose was improve, the extent was dependent on the formate feeding rate, i.e. the slope of this formate gradient. The predicted maximum growth yield of 0.7 g/g was obtained at a slope of the formate gradient of 0.21 g/l·h at a glucose concentration of about 1 g/l. Steeper gradients did not further improve this value, but rather impaired the growth yield due to the appearence of a high residual formate concentration in the fermentation medium. The yield patterns are influenced by the culture pH, a value of at least 4.8 is necessary to achieve the maximum growth yield on glucose. At lower pH formate became increasingly toxic. The ratio of formate to glucose necessary to obtain the maximum yield coefficient was 1...1.6:1 (in grams). On the basis of the energy content of formate a ratio of 1.2...1 (P/O=2) was calculated to substitute the part of glucose which is endoxidized for energy generation. Deviations from this value are explained in terms of the manner of uptake and uncoupling property of formic acid/formate and the existence of a second, formate-“wasting” enzyme.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Applied microbiology and biotechnology 20 (1984), S. 195-200 
    ISSN: 1432-0614
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary A theoretical consideration is presented of the comparative efficiency of carbon conversion of glucose by the Embden-Meyerhof-Parnas (EMP) and the oxidative hexosemonophosphate (HMP) pathways. As a result it is shown that maximum carbon conversion, that is 89%, is possible when glucose is assimilated via the EMP pathway. This value is diminished in proportion to the participation of the HMP pathway in carbon assimilation and is halved when glucose is incorporated entirely via this pathway. If NADPH is included as a source of energy, glucose may behave both as an excess carbon and an excess energy substrate, the latter being the case when greater portions of the HMP pathway operate, and the extent of this is in turn dependent on the P/O quotient. If NADPH cannot be used for ATP synthesis, glucose remains an excess carbon substrate throughout, although when the HMP pathway accounts for more than 26% of glucose assimilation an increasing excess of reduction equivalents is produced. These results are interpreted in terms of mixed-substrate utilization for improving growth yield when glucose is to be used as the excess carbon component.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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