Selective fermentation

Abstract

The factor KG/F for brewer''s yeast (BY) was not appreciably influenced by the relative proportions of glucose and fructose in the original solution. The factor was not influenced by modification of the sac-charase activity of BY by the method of Willstatter, Lowry, and Schneider. The saccharase of Sauterne yeast (SY) resembled that of BY in that it was inhibited more strongly by fructose than by glucose. Addition of saccharase to a mixture of glucose and fructose undergoing fermentation by zymin (brewer''s) did not affect the selectivity. The factor KG/F for BY decreased with rise in temp. of fermentation, while that for SY increased. BY ferments glucose faster than fructose in separate solutions when the concentration of sugar is less than 1%. SY ferments fructose faster than glucose in separate solutions at all concentrations up to 10%, but especially at low concentrations. The mutarotation of partly fermented solutions of the sugars is for glucose by BY in the positive direction, glucose by SY in the negative, fructose by BY in the positive, and fructose by SY in the negative direction. The hypothesis is advanced that BY and most yeasts are specific for that form of fructose which is present in small proportion, but which increases with temp., possibly a [gamma]-form, whereas SY is specific for the normal form.