UPTAKE AND TURNOVER OF14C GLUCOSE BY YEAST DURING WORT FERMENTATIONS

Abstract

The incorporation of randomly labelled 14C glucose, or substances derived from it, into various cell components was followed during a brewery type fermentation, using a yeast polysaccharide fractionation technique in conjunction with liquid scintillation. The labelled glucose, when added to wort, was assimilated by brewer's yeast, most of it being fermented to 14C ethanol. A small but significant amount of the 14C glucose, or its metabolites, was incorporated into the polysaccharide fractions of the yeast. Employment of a simple “swop-over” technique has shown that in two of these fractions, the low molecular weight acid-soluble material and the mannan, there was a substantial turnover, reflecting respectively the transient metabolic status of the former and the special role of mannan in the structure of the outer layer of the cell wall. Glucan, as would be expected from its function as the principal structural component of the cell wall complex, was completely stable. Glycogen was also stable, and showed no evidence of turnover, even during the later stages of the fermentation. Hence it is unlikely that it could function as an energy reserve in this strain (N.C.Y.C. 240) during primary fermentation of brewer's wort.