EFFECT OF YEAST ADAPTATION TO MALTOSE UTILIZATION ON SUGAR UPTAKE DURING THE FERMENTATION OF BREWER'S WORT

Yeast adaptation to maltose utilization diminishes the repressing effect of glucose on maltose uptake. Furthermore, it affects both the rates and profiles of maltose, glucose and maltotriose uptake during high cell density brewer's wort fermentation. Yeast cells pre-grown in maltose, as sole carbon source, and harvested while the sugar is still present in the growth medium, are better adapted to utilize maltose. The adapted cells are less sensitive to glucose inhibition, and the uptake of glucose is inhibited in the early stages of fermentation. Cells grown for longer periods and harvested following maltose depletion, lose their ability to preferentially utilize maltose. In addition, they become more sensitive to glucose repression, and are able to utilize glucose faster than the cells harvested when maltose is still present in the medium. During the process of adaptation, maltose controls the induction of its own transport systems and appears to affect the biosynthesis of the glucose transport systems.