Title: Isolation of Sake yeast by the Enrichment culture method using the antibiotic yeastcidin produced by koji-mold (Aspergillus oryzae)
Abstract: We isolated yeast that have the characteristics of sake yeast by the enrichment culture method using a synthetic medium containing an antibiotic (yeastcidin) produced by koji-mold (Aspergillus oryzac). The synthetic medium containing asparagine as a sole nitrogen source and crude yeastcidin (250 mg/l) was autoclaved and then milk casein sterilized by ethanol was added at a final concentration of 5%. The medium was adjusted to pH 3.1 with lactic acid. A total of 500 ml of syntetic medium and 1 g of soil were added to a one liter Erlenmeyer flask with a sterilized cotton plug, and then incubated at 30°C.Forty strains of Saccharomyces sp. were isolated from each synthetic medium culture containing soils obtained from the area around the sake breweries both in the presence and absence of yeastcidin.The isolated strains were tested for their sugar fermentation ability, assimilation of carbon sources, resistance against yeastcidin, froth forming ability and requirement for biotin.All forty yeast strains isolated from the synthetic medium containing yeastcidin were sake yeast type. But, 29 strains of sake yeast type and 11 strains of shochu yeast type were isolated from the synthetic medium without yeastcidin.We tried to isolate a useful sake yeast type from 20 flowers and were able to isolate Saccharomyces sp. from 14 flowers. We isolated non-froth forming sake yeast type from 3 flowers, high froth forming sake yeast type from 9 flowers and another kind of yeast from one flower.