Novel thermotolerant yeast suitable for industrial bioethanol production

A thermotolerant yeast capable of converting 100 g/L glucose to 46 g/L ethanol was isolated. The isolate was identified as a strain of Pichia kudriavzevii based on sequences generated by amplifying the 18s ribosomal DNA and a blast search on the NCBI database. The strain could grow and produce ethanol from 30 degrees C to 45 degrees C with theoretical ethanol yield above 90% and an ethanol productivity of 2 g/L/h. The strain produced ethanol at acidic pH of 1.5 and 3 at 37 degrees C and 42 degrees C respectively. At 42 degrees C, the strain could tolerate up to 10% ethanol which further increased to 15% when the temperature was reduced to 37 degrees C. Pichia kudriavzevii LC671435 could utilize peanut and soybean meal as nitrogen sources for ethanol production in addition to its ability to produce ethanol from fructose with the same efficiency as glucose. P. kudriavzevii LC671435 produced 0.47, 0.45 and 0.40 g ethanol/g glucose from 100 g/L, 160 g/L and 200 g/L glucose respectively at 42 degrees C. When used for repeated batch ethanol production, P. kudriavzevii LC671435 produced above 46 g/L ethanol up to fifth batch at 37 degrees C and fourth batch at 42 degrees C. With its thermotolerant ability, this novel isolate has great prospects for industrial fermentation at high temperature without additional cooling costs.