Abstract:

In this study, 69 thermotolerant yeast strains were isolated from 29 different soil samples, and the fermentation
performance of these strains at high temperature was also detected. Based on 26S rDNA D1/D2 domain sequence analysis
and physiological characterization, these strains were phylogenetically related to 7 species in 6 genera, including Candida
tropicalis (39.1% of the total yeast strains), K. marxianus (23.4%), I. orientalis (29.7%), M. guilliermondii (1.6%), K. bovina
(1.6%), C. palmioleophila (1.6%) and S. cerevisiae (3.1%). C. tropicalis were the most widely distributed species. The best
thermotolerant and ethanol fermentation ability were detected in K. marxianus. The ethanol production reached up to 6.56%
(V/V) in 72 h at 40 ℃. These results demonstrated that K. marxianus has obvious advantages in ethanol fermentation at high
temperature, which makes it a good potential candidate for commercial biomass ethanol production.

Key words: thermotolerant yeast, biodiversity, 26S rDNA, alcohol fermentation