Ethanol Production from Alkaline Pretreated Miscanthus Using Respiration-Deficient Thermotolerant Yeast

The major obstacle of simultaneous saccharification and fermentation (SSF) is that enzymatic hydrolysis in SSF is not conducted at optimal temperature. To overcome this obstacle, thermotolerant Saccharomyces cerevisiae strains were screened from respiration-deficient mutants induced by ethidium bromide. Among the mutant strains, S. cerevisiae mbc 2 was selected as the most suitable strain for fermentation at 42°C. Meanwhile, Miscanthus was prepared as substrates after pretreatment with 1.5 M NaOH at 150°C for 30 min. Next, SSF was conducted with pretreated Miscanthus containing 3% glucan to estimate the fermentability of S. cerevisiae mbc 2 at 42°C. In results, ethanol concentration of 15.3 g/L was achieved by S. cerevisiae mbc 2 in 48 h, representing 90.1% of theoretical ethanol yield. Furthermore, SSF with increased substrate concentration up to 9% glucan resulted in 82.2% of theoretical ethanol yield. Thus, this approach for SSF with high solid loading using thermotolerant S. cerevisiae mbc 2 might contribute to processes and microbial strain development for ethanol production from lignocellulosic biomass.