Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
The use of thermotolerant fuel ethanol-producing yeast has the advantage in reducing cooling costs, faster fermentation rates, and decreased contamination chances during fermentation. The use of low-pH-tolerant yeast has the merit in fermenting acid-pretreated feedstock. The improvement of thermotolerance of a Saccharomyces cerevisiae industrial strain was performed by genome shuffling. The starting population was generated by the treatment of ultraviolet ray or N-methyl-N'-nitro-N-nitrosoguanidine. The mutants were screened for growth at 42°C on YPD-agar plates. Characterization of selected mutants and wild-type strain indicated the two phenotypes of themotolerance and ethanol yield were improved. The selected mutants were then subjected to multi-parental hybridization. The resulting hybrids were screened for enhanced thermotolerance and ethanol production. The best performing strain exhibited growth at 42°C on a YPD agar plate with 10-5 diluted cell-suspension in the serial dilution assay. The cells of the thermotolerant strain were irradiated again by UV, and the resulting cells were plated onto a YPD agar plate with pH of 2.9 for cultivation. One selected strain exhibited high growth rate at pH 2.9, whereas the original strain could not grow in the same condition.