ENERGETICS OF SACCHAROMYCES-CEREVISIAE IN ANAEROBIC GLUCOSE-LIMITED CHEMOSTAT CULTURES

The energetics of Saccharomyces cerevisiae were studied in anaerobic glucose-limited chemostat cultures via an analysis of biomass and metabolite production. The observed Y(ATP) was dependent on the composition of the biomass, the production of acetate, the extracellular pH, and the provision of an adequate amount of fatty acid in the medium. Under optimal growth conditions, the Y(ATP) was approximately 16 g biomass (mol ATP formed)-1. This is much higher than previously reported for batch cultures. Addition of acetic acid or propionic acid lowered the Y(ATP). A linear correlation was found between the energy required to compensate for import of protons and the amount of acid added. This energy requirement may be regarded as a maintenance energy, since it was independent of the dilution rate at a given acid concentration.