| Summary: | The yeast <i>Saccharomyces cerevisiae</i> has been widely applied in fermentation industries, chemical industries and biological research and it is widespread in different environments, especially in sugar-rich environments. However, little is known about the occurrence, distribution and roles of <i>S. cerevisiae</i> in marine environments. In this study, only 10 strains among all the yeasts isolated from different marine environments belonged to <i>S. cerevisiae</i>. It was found that most of the strains of <i>S. cerevisiae</i> in marine environments occurred in guts, the surface of marine fish and mangrove trees. In contrast, they were not found in seawater and sediments. All the strains of <i>S. cerevisiae</i> isolated from the marine environments had a lower ability to produce ethanol than the highly alcohol-producing yeast <i>Saccharomyces</i> sp. W0 isolated from fermented rice, but the strains 2E00400, 2E00558, 2E00498, 2E00723, 2E00724 could produce higher concentrations of ethanol than any other marine-derived strains of <i>S. cerevisiae</i> obtained in this study. However, some of them had higher ethanol tolerance and higher trehalose content than <i>Saccharomyces</i> sp. W0. In particular, ethanol tolerance of the yeast strain 2E00498 was higher than that of <i>Saccharomyces</i> sp. W0. This may be related to the harsh marine environments from which they were isolated. Such yeast strains with higher alcohol tolerance could be used to further improve the alcohol tolerance of <i>Saccharomyces</i> sp. W0.
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