Mischsubstratfermentation – ein energetisch begründetes Konzept

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Abstract
On the basis of the combustion enthalpy of microbial biomasses carbon substrates for the aerobically heterotrophic growth of microorganisms can be divided into substrates with energy excess (e.g. ethanol, n‐alkanes) and with energy deficit (or carbon excess, e.g. acetate, glucose). By combining substrates having different carbon energy ratios from both groups in a certain mixing proportion an improvement of the yield coefficients linked to a reduction of the specific heat production (kJ/g dry weight), an increase of the growth rate (h−1) and the velocity of the substrate utilization ought to be possible on condition that the co‐ or auxiliary‐substrate does not cause inhibition or (catabolite‐) repression effects.There are some examples corroborating the theoretical concept, e.g. the combinations ethanol/sucrose‐Candida utilis, methanol/xylose‐Hansenula polymorpha. In each case the specific growth rate and the yield coefficient on the mixture were higher than on any single substrate of the combination.Thermochemical methods are suitable for the optimizing the substrate mixing proportion.