Effect of Sugars on d -Arabitol Production and Glucose Metabolism in Saccharomyces rouxii

Abstract

The effect of sugars on the production of D-arabitol and on the glucose catabolic pathways was investigated in the osmtrophic yeast S. rouxii. The activity of D-arabitol dehydrogenase, which served as a measure of total D-arabitol production, increased when cells were grown in the presence of increasing glucose concentrations. Growth in sucrose had no effect on the enzyme activity. A high intracellular concentration of D-arabitol could be demonstrated when the cells were grown in a 60% glucose medium and could be eliminated by anaerobic growth or growth in the presence of 4 mg of chloramphenicol/ml. A mutant was isolated that would not grow in 60% glucose; although the regulation of D-arabitol dehydrogenase was altered in th1s strain, the production of D-arabitol was not eliminated. The activity of D-arabitol dehydrogenase followed the growth phases of the parent strain when the cells were preadapted to 30% glucose. If the cells were adapting from 1-30% glucose, a large increase in enzyme activity was detected before growth occurred. Protein synthesis was involved in this increase in activity. There was an increased participation of the pentose phosphate pathway when the cells were grown in the presence of increasing glucose concentrations. The mutant strain had only an 11% pentose phosphate pathway participation compared with 20% for the parent strain in glucose. Apparently, the active pentose phosphate pathway is involved in glucose tolerance by providing a plentiful supply of NADPH which is necessary for cell survival.