5i. the Formation of Succinic- Acid in Yeast

PASTEUR [1860] was the first to observe succinic acid among the substances formed during alcoholic fermentation. In his experiments the yield of succinic acid was 0-5-0 7 % of the fermented sugar. Ehrlich [1909] found that fermenting yeast is capable of converting glutamic acid into succinic acid and advanced the view that all the succinic acid formed during fermentation is derived from glutamic acid; the latter was assumed to arise from the autolysis of dead yeast cells. This view has been widely accepted. It will be shown in this paper that in addition to Ehrlich's mechanism there is a second mechanism of succinic acid formation in which sugar is the parent substance. Under normal conditions most, if not all, of the succinic acid is derived from this source. EXPERIMENTAL