Induction of oxidofermentative ethanol formation in recombinant cells of Saccharomyces cerevisiae yeast

So-called Crabtree-positive yeasts, such as Saccharomyces cerevisiae, ferme nt glucose to ethanol even under fully aerobic conditions, when the sugar i s present in excess. This metabolic behaviour leads to a decrease of the bi omass yield and it is therefore disadvantageous for recombinant protein pro duction. Using a strain of Sacch. cerevisiae expressing garlic alliin lyase , we found that the specific glucose uptake rate is an important parameter for the induction of oxidofermentative metabolism, with a threshold value f or the onset of ethanol formation of 0.2 g g(-1) h(-1) (glucose per dry bio mass and hour). It can be concluded that an optimal production process has to nln under strict control of glucose feeding in order not to exceed this critical value of specific glucose uptake rate.