MODELLING OF MICROBIOLOGICAL PROCESSES AND KINETIC CONVERSION RATES IN SACCHAROMYCES CEREVISIAE FERMENTATION PROCESSES

Abstract

Metabolic pattern of a given micro-organism is an inherent character controlled by the genetic background of the organism. Yeast are important micro-organisms that underwent different genetic studies for the improvement of growth or product formation. In the present study, the bakers' yeast Saccharomyces cerevisiae was investigated referring to substrate conversion rates as well as growth kinetics under different fermentation processes. This work comprised of five parts, in each of which a certain fermentation process was dealt with. In the first part, two different strains of S.cerevisiae that differ in the genetic make up were chosen. The first S.cerevisiae K88 is a prototroph, that results from the mating of two mutants and resembles the wild type in its properties, and the second is a mutant suffering from the deficiency of. Phosphofructokinase enzyme regulation; to study their fermentative characters under different conditions in shacked flasks and in 1OL fermentor, Biostat E. In this part the effect of different aeration conditions through the variation of the number of baffles as well as the medium volume in the shaking flasks for both strains was investigated, where it was found that, under the investigated conditions, no direct effect of the aeration rate variation on the rate of glucose consumption as well as the ethanol production rate. Then the ethanol tolerance was investigated and it was found that 8% and 10% ethanol added to the culture after 4.5 h. of the fermentation beginning would inhibit the growth ofboth strains.