Co-consumption of sugars or ethanol and glucose in a Saccharomyces cerevisiae strain deleted in the HXK2 gene

0In previous studies it was shown that deletion of the HXK2 gene in Sacchar omyces cerevisiae yields a strain that hardly produces ethanol and grows al most exclusively oxidatively in the presence of abundant glucose. This pape r reports on physiological studies on the hxk2 deletion strain on mixtures of glucose/sucrose, glucose/galactose, glucose/maltose and glucose/ethanol in aerobic batch cultures. The hxk2 deletion strain co-consumed galactose a nd sucrose, together with glucose. In addition, co-consumption of glucose a nd ethanol was observed during the early exponential growth phase. In S. ce revisiae, co-consumption of ethanol and glucose (in the presence of abundan t glucose) has never been reported before. The specific respiration rate of the hxk2 deletion strain growing on the glucose/ethanol mixture was 900 mu mol . min(-1) . (g protein)(-1), which is four to five times higher than t hat of the hxk2 deletion strain growing oxidatively on glucose, three times higher than its parent growing on ethanol (when respiration is fully derep ressed) and is almost 10 times higher than its parent growing on glucose (w hen respiration is repressed). This indicates that the hxk2 deletion strain has a strongly enhanced oxidative capacity when grown on a mixture of gluc ose and ethanol. Copyright (C) 2001 John Wiley & Sons, Ltd.