초록
<P><B>Abstract</B></P><P>To investigate the bioethanol production from sweet potato, the saccharification and fermentation conditions of co-immobilization of saccharolytic molds (<I>Aspergillus oryzae</I> and <I>Monascus purpureus</I>) with <I>Saccharomyces cerevisiae</I> were analyzed. The immobilized yeast cells showed that at 10% glucose YPD (yeast extract peptone dextrose) the maximum fermentation rate was 80.23%. Viability of yeasts cells were 95.70% at a final ethanol concentration of 6%. Immobilization enhanced the ethanol tolerance of yeast cells. In co-immobilization of <I>S. cerevisiae</I> with <I>A. oryzae</I> or <I>M. purpureus</I>, the optimal hardening time of gel beads was between 15 and 60 min. Bioethanol production was 3.05–3.17% (v v<SUP>−1</SUP>) and the Y<SUB>E/s</SUB> (yield of ethanol production/starch consumption) was 0.31–0.37 at pH 4, 30 °C and 150 rpm during 13 days fermentation period. Co-immobilization of <I>S. cerevisiae</I> with a mixed cultures of <I>A. oryzae</I> and <I>M. purpureus</I> at a ratio of 2:1, the bioethanol production was 3.84% (v v<SUP>−1</SUP>), and the Y<SUB>E/s</SUB> was 0.39 for a 11 days incubation. However a ratio of <I>A. oryzae</I> and <I>M. purpureus</I> at 1:2 resulted a bioethanol production rate of 4.08% (v v<SUP>−1</SUP>), and a Y<SUB>E/s</SUB> of 0.41 after 9 days of fermentation.</P> <P><B>Highlights</B></P><P>► We develop and evaluate a single-step system for bioethanol fermentation. ► This system was using a co-immobilization method for the fungi and yeast. ► The mixed blends of molds and <I>S. cerevisiae</I> gave the highest ethanol yields. ► The maximum ethanol production was 4.08% (v v<SUP>−1</SUP>) when the <I>Aspergillus</I>:<I>Monascus</I> (A:M) ratio was 1:2.</P>