Saccharomyces cerevisiae Mutants Resistant to Catabolite Repression: Use in Cheese Whey Hydrolysate Fermentation.

Mutants of an industrial-type strain of Saccharomyces cerevisiae which rapidly and completely fermented equimolar mixtures of glucose and galactose to ethanol were isolated. These mutants fell into two general phenotypic classes based upon their fermentation kinetics and enzyme induction patterns. One class apparently specifically effects the utilization of galactose and allows sequential utilization of first glucose and then galactose in an anaerobic fermentation. The second class of mutants was resistant to general catabolite repression and produced maltase, invertase, and galactokinase in the presence of repressive levels of glucose. These mutants were completely dominant and appear to represent an as yet undescribed class of mutant.