A 2-Deoxyglucose-Resistant Mutant of Saccharomyces cerevisiae Shows Enhanced Maltose Fermentative Ability by the Activation of MAL Genes

Saccharomyces cerevisiae MCD4 is a 2-deoxyglucose (2-DOG)-resistant mutant derived from the wild-type strain, AK46, wherein the 2-DOG resistance improves the maltose fermentative ability. In the MAL gene cluster, mutations were detected in MAL11 and MAL31, which encode maltose permeases, and in MAL13 and MAL33, which encode transcriptional activators. In maltose medium, the expression of MAL11 and MAL31 in MCD4 was 2.1 and 4.2 times significantly higher than that in AK46, respectively. Besides, the expression of MAL13 and MAL33 also tended to be higher than that of AK46. Although no mutations were found in MAL12 and MAL32 (which encode α-glucosidases), their expression was significantly higher (4.9 and 4.4 times, respectively) than that in AK46. Since the expression of major catabolite repression-related genes did not show significant differences between MCD4 and AK46, these results showed that the higher maltose fermentative ability of MCD4 is due to the activation of MAL genes encoding two maltose permeases and two α-glucosidases.