Enzyme formation in Saccharomyces fragilis. 1. Invertase and raffinase

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Abstract
The ability of washed cell suspensions of Saccharomyces fragilis to ferment glucose, sucrose, galactose, lactose and raffinose following growth in a basal medium, either unsupplemented or supplemented with one of these sugars, was studied. Ability to ferment galactose, lactose or raffinose is an adaptive property in S. fragilis. Following growth in basal medium plus 10% glucose, washed-cell suspensions of S. fragilis do not acquire ability to ferment galactose, lactose or raffinose when incubated with these sugars in phosphate buffer, pH 5.0, for 6 hrs. The initial ability of such cell suspensions to ferment sucrose is very low, but when incubated with sucrose and phosphate buffer for 2 hrs. fermentation rate increases to that for glucose fermentation. This increase is prevented by 3 x 10-4[image]-Na azide. The increase in rate of sucrose fermentation is accompanied by an increase in invertase activity, sufficient to account for increase in fermentation rate. The increase in invertase activity is most rapid with very young cells and at pH 4.5.5.0, and does not occur in the presence of Na azide. Following growth in unsupplemented basal medium, washed-cell suspensions of S. fragilis can acquire the ability to ferment raffinose, lactose and galactose, the rate of adaptation decreasing in that order. Adaptation does not occur in the presence of Na azide. The initial rate of glucose and fructose fermentation by these suspensions is very low and max. rate is not reached for 2 hrs., the increase in rate being prevented by Na azide. Failure to ferment raffinose following growth in unsupplemented basal medium is not due to lack of hydrolytic activity towards raffinose, but appears to be due to a deficiency in the glycolytic system. Evidence is presented which suggests that glucose and fructose strongly inhibit invertase synthesis by S. fragilis.