Abstract
Isolation and screening of thermotolerant yeast capable of producing ethanol at high temperatures were described
in this study. Soil, plant decay and sugarcane bagasse samples from sugarcane plantations and sugar factories
in Udorn Thani, Khon Kaen, Nong Bue Lum Pu, Chaiyaphumi, Kalasil, Roi Ed and Nakorn Ratchasima province were
collected and subjected to the isolation of thermotolerant yeast by using the enrichment culture technique. A total of 84
isolates of yeast were obtained and 43 isolates of them showed their ability to grow at temperature up to 45oC. Fifteen
isolates of yeast could grow in the medium containing up to 10% (v/v) ethanol. Almost of the isolated yeasts utilized
hexose sugars such as glucose, fructose and sucrose as carbon sources, while only 15 isolated yeasts utilized pentose
sugars such as xylose and arabinose as carbon sources. Of 43 isolates of yeast, 19 isolates showed their ability to
produce high concentration of ethanol at high temperatures. Molecular identification of the yeast based on the D1/D2
domain of 26s rDNA sequencing revealed that these 19 isolated yeasts belonged to the genus Candida sp., Pichia sp.
and Issatchenkia sp.