Physiological characterization of a new thermotolerant yeast strain isolated during Brazilian ethanol production, and its application in high-temperature fermentation

Background The use of thermotolerant yeast strains can improve the efficiency of ethanol fermentation, allowing fermentation to occur at temperatures higher than 40 °C. This characteristic could benefit traditional bio-ethanol production and allow simultaneous saccharification and fermentation (SSF) of starch or lignocellulosic biomass. Results We identified and characterized the physiology of a new thermotolerant strain (LBGA-01) able to ferment at 40 °C, which is more resistant to stressors as sucrose, furfural and ethanol than CAT-1 industrial strain. Furthermore, this strain showed similar CAT-1 resistance to acetic acid and lactic acid, and it was also able to change the pattern of genes involved in sucrose assimilation ( SUC2 and AGT1 ). Genes related to the production of proteins involved in secondary products of fermentation were also differentially regulated at 40 °C, with reduced expression of genes involved in the formation of glycerol ( GPD2 ), acetate ( ALD6 and ALD4 ), and acetyl-coenzyme A synthetase 2 ( ACS2 ). Fermentation tests using chemostats showed that LBGA-01 had an excellent performance in ethanol production in high temperature. Conclusion The thermotolerant LBGA-01 strain modulates the production of key genes, changing metabolic pathways during high-temperature fermentation, and increasing its resistance to high concentration of ethanol, sugar, lactic acid, acetic acid, and furfural. Results indicate that this strain can be used to improve first- and second-generation ethanol production in Brazil.