Screening of thermotolerant yeast isolated from sugarcane plantations in Northeastern part of Thailand

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.