ABSTRACT
Hybridization by spore conjugation was used to develop new and improved wine yeasts of Saccharomyces cerevisiae. The procedure was achieved with diploid, homothallic strains with high sporulation frequency and high spore viability. The method was verified by crossing flocculent and non-H(2)S-forming strains. Single-spore descendants of the hybrids were studied by tetrad analysis with regard to the aforementioned characters and the other two winemaking traits, i.e., ethanol production and fermentation rate. A highly flocculent, non-H(2)S-forming wine yeast strain with a high fermentation rate and high ethanol production was obtained.
ABSTRACT
A procedure for inducing mutants of a homothallic strain of Saccharomyces cerevisiae is described. The essential parts of the procedure are long incubation in Glusulase, which preferentially kills vegetative cells instead of spores, and treatment in 9% ethyl methanesulfonate, which also preferentially kills vegetative cells instead of spores. Consequently, the viable population is virtually 100% spores.
Subject(s)
Mutation , Saccharomyces cerevisiae/genetics , Ethyl Methanesulfonate/toxicity , Glucuronidase/toxicity , Multienzyme Complexes/toxicity , Saccharomyces cerevisiae/drug effects , Saccharomyces cerevisiae/physiology , Spores, Fungal/drug effects , Spores, Fungal/physiology , Sulfatases/toxicityABSTRACT
A number of strains of Saccharomyces which produce sulphite by sulphate reduction were examined from an enzymatic and genetic point of view. There are a number of mechanisms that regulate this activity. All of these mechanisms involve the sulphite-reducing activity. In the strains examined, reduced function as a result of mutation in the Sr-locus (affecting H2S-NADP oxidoreductase EC 1.8.1.2), repression of biosynthesis of the enzyme because of a mutation below the specific locus, and inhibition of the enzyme by endogenous factors were found to be responsible. The production of sulphite can also be connected with a complex state of heterozygosity. It is probably this multiplicity of biochemical and genetic mechanisms that accounts for the frequency with which the production of sulphite is observed in wild strains in nature.
