Bioethanol Production from Sweet Potato (Ipomoea batatas L.) by Enzymatic Liquefaction and Simultaneous Saccharificationand Fermentation (SSF) Process

摘要

The starch content in sweet potato (Ipomoea batatas var. Sankar) flour and fresh tubers was liquefied by treatment with 0.08% (v/w) commercial thermostable alpha-amylase (Termamyl, Novozyme, Denmark) and 0.33% (v/w) amyloglucosidase (AMG~R, Novozyme,Denmark). The hydrolysate was subsequently fermented with a thermotolerant strain of Saccharomyces cerevisiae into ethanol. The result showed that the final ethanol yield of 240 and 235 g.kg"' (flour) and 96 and 93 g.kg~(-1) (tuber), was little influenced by liquefaction conditions i.e. 80 deg C for 2 h and 90 deg C for 1 h, respectively in conjunction with treatment of 0.33% (v/w) AMG (45 deg C for 24 h) Similarly, the treatment of AMG for 45 deg C for 48h and 45 deg C for 24 h had little effect on theultimate ethanol yield, i.e. 242 and 238 g.kg~(-1) (flour) and 94 and 93 g.kg~(-1) (tuber), respectively after liquefaction (90 deg C for 1 h) treatment. Another experiment was designed to study simultaneous saccharification and fermentation by saccharifying the liquefied (90 deg C for 1 h) hydrolysate and co-fermenting with S. cerevisiae at 40 deg C for 96 h. The ethanol yield was 258 g.kg~(-1) for flour and 95 g.kg~(-1) for tuber, respectively.