THE ASSIMILATION AND DEGRADATION OF CARBOHYDRATES BY YEAST CELLS

Abstract

In a previous paper (1) the results of a preliminary investigation of the assimilation and breakdown of glucose during the course of its fermentation by living yeast cells were given. Early in the course of the fermentation, the formation of usual products was much slower than the disappearance of the glucose. In other words the products that were determined failed to account for all the glucose used by the cells. Therefore, some of the glucose was in an unanalyzed form. However, as the fermentation progressed toward completion, the quantity of glucose in an unanalyzed form diminished. This failure of the usual products of fermentation to account for all the glucose utilized in the initial stage of fermentation has been noted by other investigators, but there is little agreement as to the reason for the discrepancy. WillstZtter and Rohdewald (2) claimed that the sugar was quickly converted to glycogen, which fermented at a slower rate. Kruyk and Klingmiiller (3) investigated the phenomenon but were unable to account for the disappearance of the sugar on the basis of glycogen formation. Fales and Baumberger (1) tentatively assume t,hat intermediary products accumulated during the initial stage of fermentation. Wertheimer (4) reported in 1929 that a large fraction (one-seventh to one-half) of the sugar, not accounted for otherwise during the initial period of fermentation, could be recovered in the alkali-insoluble carbohydrate fraction of the yeast cell. This report was completely overlooked by later investigators of the problem. The purpose of this paper is to report the results of a study of the synthesis and degradation of yeast carbohydrat,es during exogenous metabolism in the presence and absence of oxygen and during starvation. The total, the alkali-stable, the alkali-soluble, and the alkali-insoluble, carbohydrate fractions were determined during the course of the reactions.