초록
<P><B>Abstract</B></P> <P>One major obstacle of simultaneous saccharification and fermentation (SSF) is that enzymatic hydrolysis in SSF is conducted at non-optimal temperature. To break through this bottleneck, thermotolerant <I>Saccharomyces cerevisiae</I> strains mbc 1-4 were screened by spot-assay from respiration-deficient mutants induced by ethidium bromide. When four strains placed in liquid medium, the strains exhibited significant increased growth and fermentability at 42 °C in comparison to the host. Consequently, <I>S. cerevisiae</I> mbc 2 was selected to be the most suitable for bioethanol production at 42 °C. <I>Miscanthus</I> was pretreated with 1.5 M NaOH at 150 °C for 30 min in 1 L-vessel. As a result, 42.6% of solids containing 77.9% cellulose were recovered. Next, SSF was conducted with pretreated <I>Miscanthus</I> containing 3% glucan to estimate the fermentability of <I>S. cerevisiae</I> mbc 2 at 42 °C. In results, Ethanol concentration and theoretical ethanol yield by <I>S. cerevisiae</I> mbc 2 in 48 h were 15.3 g/L and 90.1%, respectively, whereas those by the control were 8.3 g/L and 49.3%, respectively. In addition, SSF with increased substrate concentration upto 9% glucan resulted in 86.3% and 82.2% of theoretical ethanol yield, respectively. Thus, our approach for SSF with high solid loading using thermotolerant <I>S. cerevisiae</I> mbc 2 contributes to process and microbial strain development for bioethanol production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel thermotolerant yeast strains were induced and isolated by random mutagenesis using EtBr. </LI> <LI> The thermotolerant strains were verified to grow and ferment better than its control at 42 °C. </LI> <LI> The selected strain mbc 2 was verified to be suitable for SSF of pretreated <I>Miscanthus</I> at 42 °C. </LI> <LI> Furthermore, the selected strain mbc 2 was proven to be suitable for SSF with high solids loading of <I>Miscanthus.</I> (e.g., 9% glucan). </LI> </UL> </P>