Hybridization and Selection of Saccharomyces cerevisiae Strains from Industrial Baker’s Yeasts

Hybridization study of two Saccharomyces cerevisiae baker’s yeast strains isolated in Thailand, IFRPD 6080 and IFRPD 6081, was carried out. Rare-mating technique has been employed with haploid and diploid mating strains of Japanese baker’s yeast. Polyploid (triploid and tetraploid) hybrids produced from rare-mating were selected and induced for sporulation. Screening of segregants obtained from individual spore clones of the hybrids was performed by determination of their characteristics, i.e. yield of yeast after cultivation, total carbohydrate and trehalose contents of obtained yeast, and carbon dioxide (CO2) production during fermentation with bread dough. Two segregants, 6080xs4D s27 and 6080xs4D s39 derived from the parental strain IFRPD 6080 and one segregant, 6081xs34D s12 from the parental strain IFRPD 6081, with desirable characteristics were obtained as the new strains. These segregants possessed good growth yield and higher maltose fermentation ability than their parents. Carbon dioxide productions in non-sugar, low-sugar and high-sugar dough were also markedly improved. Moreover, the strain 6080xs4D s27 acquired certain freeze-tolerant ability from mating strain and was able to use for frozen dough preparation.