Induction of Oxidofermentative Ethanol Formation in Recombinant Cells of Saccharomyces cerevisiae Yeast

Robert Weik¹, Gerald Striedner¹, Andrej Francky², Peter Raspor², Karl Bayer¹ and Diethard Mattanovich¹*

¹ Institut für Angewandte Mikrobiologie, Universität für Bodenkultur Wien Muthgasse 18, A-1190 Vienna, Austria
² Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, Sl-1000 Ljubljana, Slovenia

Article history:
Received May 6, 1998
Accepted June 14, 1999

Key words:
Saccharomyces cerevisiae, Crabtree effect, chemostat culture, recombinant alliin lyase

Summary:
So-called Crabtree-positive yeasts, such as Saccharomyces cerevisiae, ferment glucose to ethanol even under fully aerobic conditions, when the sugar is present in excess. This metabolic behaviour leads to a decrease of the biomass yield and it is therefore disadvantageous for recombinant protein production. 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 for the onset of ethanol formation of 0.2 g g^–1 h^–1 (glucose per dry biomass and hour). It can be concluded that an optimal production process has to run under strict control of glucose feeding in order not to exceed this critical value of specific glucose uptake rate.   

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