NADH reoxidation does not control glycolytic flux during exposure of respiring Saccharomyces cerevisiae cultures to glucose excess

Introduction of the Lactobacillus casei lactate dehydrogenase (LDH) gene in to Saccharomyces cerevisiae under the control of the TPII promoter yielded high LDH levels in batch and chemostat cultures. LDH expression did not aff ect the dilution rate above which respiro-fermentative metabolism occurred (D-c.) in aerobic, glucose-limited chemostats. Above D-c, the LDH-expressin g strain produced both ethanol and lactate, but its overall fermentation ra te was the same as in wild-type cultures. Exposure of respiring, LDH-expres sing cultures to glucose excess triggered simultaneous ethanol and lactate production. However, the specific glucose consumption rate was not affected , indicating that NADH reoxidation does not control glycolytic flux under t hese conditions. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.