CLASSIFICATION OF CRYOPHILIC WINE YEASTS BASED ON ELECTROPHORETIC KARYOTYPE, G+C CONTENT AND DNA SIMILARITY

Seven strains of cryophilic wine yeasts and two strains of mesophilic wine yeasts were investigated for their utilization of sugars, viability of ascospores in hybrid obtained from between cryophilic wine yeast and mesophilic wine yeast, electrophoretic karyotype, G + C content of DNA and DNA similarity in photobiotin microplate-hybridization. Six strains of cryophilic wine yeasts were identified as Saccharomyces uvarum and one strain of cryophilic wine yeast was identified as S. chevalieri according to The Yeasts, 2nd ed. (Lodder, J., ed., North Holland Publ. Co., Amsterdam, 1970) on the basis of mainly sugar utilization. However, ascospores of hybrids obtained from between cryophilic wine yeast and mesophilic wine yeast did not germinate. These cryophilic wine yeasts were similar to the type strain of S. bayanus (IFO 1127) in electrophoretic karyotype and G+C content. The cryophilic wine yeasts also showed high DNA similarity values to the type strain of S. bayanus and low DNA similarity values to the type strain of S. cerevisiae (IFO 10217). Accordingly, these seven strains of cryophilic wine yeasts were classified to S. bayanus. Additionally, another eight strains of S. bayanus, classified on the basis of DNA similarity, showed good fermentability at low temperatures accompanied by production of low amounts of ethanol at intermediate temperatures, the same as cryophilic wine yeasts. These results suggest that the fermentation characteristics are specific for S. bayanus. Two strains of mesophilic wine yeasts showed high DNA similarity values to the type strain of S. cerevisiae.