Detection of maltose fermentation genes in the baking yeast strains of Saccharomyces cerevisiae

The presence of any one of the five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4 and MAL6) confers the ability to ferment maltose on the yeast Saccharomyces cerevisiae. Each locus is composed of three genes encoding maltose permease, alpha-glucosidase and MAL activator. Chromosomal DNA of seven representative baking strains has been separated by pulse-field gel electrophoresis and probed with three genes in MAL6 locus. The DNA bands to which all of the three MAL-derived probes simultaneously hybridized were chromosome VII carrying MAL1 in all of the strains tested, chromosome XI carrying MAL4 in six strains, chromosome III carrying MAL2 in three strains and chromosomes II and VIII carrying MAL3 and MAL6, respectively, in the one strain. The number of MAL loci in baking strains was comparable to those of brewing strains.