Construction of α-Galactosidase-Positive Strains of Industrial Baker's (Saccharomyces cerevisiae) Yeasts. Gregory P. Casey, Department of Applied Microbiology and Food Science (Food Biotechnology Group), and Wei Xiao and G. H. Rank, Department of Biology, University of Saskatchewan, Saskatoon, Canada S7N 0W0. J. Am. Soc. Brew. Chem. 46:0067, 1988.

An integrating vector was constructed containing the SMR1-410 resistance allele as a selectable marker and the MEL1 gene as a source of melibiase (α-galactosidase). Restriction endonuclease site-directed integration at the ILV2 locus and selection for the SM resistance phenotype resulted in stable integrates in laboratory and prototrophic production strains of Saccharomyces cerevisiae baker's yeast. A combination of formal genetic analyses and Southern hybridizations to chromosomal preparations (CHEF) and genomic digests showed single copy integration into chromosome XIII at the ILV2 locus. Expression of MEL1 under galactose induction was observed in cellular and extracellular fractions in laboratory and production strains. The vector system employed can be used as a general vehicle for gene transfer into prototrophic strains of S. cerevisiae.

Keywords: Gene transfer, α-Galactosidase, Saccharomyces cerevisiae