Development of a simple isolation method for yeast Saccharomyces cerevisiae with high fermentative activities from coastal waters

In this study, the development of a simple isolation method for obtaining yeast Saccharomyces cerevisiae with high fermentative activities from coastal waters was examined. 824 isolates were obtained on YPD2 (glucose 2 %) solid medium from coastal waters of both Tokyo Bay and Sagami Bay in Japan. In the first screening from the isolates, 221 of the 824 yeasts had fermentative activities in YPD2 liquid medium by a Durham pipe test. In the second one, 55 of the 221 yeasts had fermentative activities in YPD30 (glucose 30 %) liquid medium by the same test. In the third one, exact amounts of gas produced by the 55 strains were rapidly measured by a syringe test and the gas productivities of the 29 strains were higher than that of a marine-derived Saccharomyces cerevisiae C19 which was isolated and used for bioethanol production in previous studies (Takagi et al., 2015; Obara et al., 2015; Obara et al., 2012). Above all, the best 4 strains with the highest gas producing activities among the 29 ones were also identified as Saccharomyces cerevisiae. Thus, the yeast species S. cerevisiae was found to be simply isolated from coastal waters by the method as above. In addition, ethanol productivities of 10 strains randomly selected from the 29 ones were measured. There was an almost linear relationship between ethanol and gas productivities in the 10 strains. Therefore, bioethanol productivities of the yeast isolates from coastal waters could be speculated by measuring amounts of gas produced by the syringe test.