The Adaptive Enzymes of Certain Strains of Yeasts

Abstract

There are 2 probable causes of variation in fermentation abilities of microorganisms. A mutant may occur which can produce a fermentation not characteristic of the organisms, or, an adaptive enzyme may be formed as a direct result of a chemical stimulation of the cell. The present study deals with the latter theory and its application to yeasts. In this study, 9 strains of yeast were selected from the following species: Saccharomyces cerevisiae, S. ellipsoideus, S. carlsbergensis, and Schizosaccharomyces pombe. 9 C sources were used in the fermentations: glucose, mannose, galactose, sucrose, raffinose, maltose, melezitose, [alpha]-methyl-glucoside, and trehalose; of these only glucose, mannose. sucrose, and raffinose were fermented by all strains regardless of the C source, that is[long dash]these C sources were fermented by constitutive enzymes. Galactozymase was found to be constitutive only for S. cerevisiae, while in every other instance, galactose was fermented only by cells grown in that specific substrate; i.e., the enzyme was adaptive. Within the maltase complex there is evidence that the action of an enzyme may not be the question of a substance specificity, but, rather, a specificity for a certain group or linkage. There seemed to be some relationship between maltase, melezitase, [alpha]-methylglucosidase, and possibly trehalase. Instances occurred in which each of these 4 C sources was fermented by cells grown in maltose, in melezitose, or in [alpha]-methylglucoside, but not when the cells were grown in other substrates. Maltose was found to be fermented by a constitutive enzyme by 5 of the 9 strains. In other strains, the fermentation of maltose seemed to be adaptive. A strain of S. ellipsoideus fermented this sugar only when the cells were grown in the presence of maltose and melezitose. [alpha]-methylglu-cosidase was found to be constitutive with a strain of Schizosaccharomyces pombe, and to be somewhat of an adaptive nature with a strain of Saccharomyces ellip-soideus.