Isolation and hybridization of high temperature tolerant killer wine yeasts

Abstract

Five out of 1,190 strains of yeast, which had been isolated from variuos food and from culture collection of Institute of Food Research and Product Development (IFRPD), -Kasetsart University, exhibited killing activity against sensitive tester strain at elevated temperature (37°C and 40°C). Four selected strains i.e., No. 23, 50, 265 and 266 were identified to be Saccharomyces cerevisiae and the other i.e., KY 78 was Hansenula aturnus. Only Saccharomyces cerevisiae No.266 which had the strongest killing ability and highest killing stability was selected to be parental killer yeast strain. The main objective of this investigation is to produce a high emperature tolelant killer wine yeast. The genetic analysis of wine yeast (strain No. 2) and killer yeast (strain No. 266) was done. Both strains were induced auxotrophic markers by using ethylmethanesulfonate and then crossed the different marked strains together. Complementary genetic markers were used in hybridization to facilitate hybrid recovery. The genotype of the selected strain No.2 was a his (heterothallic) while the genotype of the selected strain No. 266 was a/∝ lys (homothallic). Spore-to-cell mating was used in this research, so that killer wine yeast strain having extended ranges of desirable characteristics can be obtained by genetic techniques. The hybrid could fermented at nearly the same rate as the parental wine strain (No.2) and also had the killing ability as the parental killer strain (No. 266).