| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1993: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
Two inulinases, P-IA (MW 70,000) and P-IB (MW 68,000), were purified from the culture filtrate of an inulinase-hyperproducing mutant, Aspergillus niger 817, grown on sucrose by DEAE-Cellulofine A-500 and Q-Sepharose HP chromatographies.The specific activities were 350 U/mg for P-IA and 340 U/mg for P-IB.The enzymes were active only toward inulin, and lacked activity toward sucrose, raffinose or levan. The main products of inulin hydrolysis were inulotriose and -tetraose. Thus, both inulinases exhibited the endotype mode of action on inulin. The apparent K_m values for inulin were 0.48 mM for P-IA and 0.50 mM for P-IB at 40ﾟC and pH 5.0.
Pure nonhydrolyzed inulin was directly converted to ethanol in a simultaneous saccharification and fermentation process. A.niger 817 was grown in a submerged culture at 30ﾟC for 5 days. The inulin-digestive liquid culture (150 ml) was supplemented with 45 g of inulin, 0.45 g of (NH_4)_2SO_4, and 0.15 g of KH_2PO_4. The medium (pH 5.0) was inoculated with an ethanol-tolerant strain, Saccharomyces cerevisiae 1200, and fermentation was conducted at 30ﾟC.An additional 30 g of inulin was added to the culture after 15 h of fermentation. S.cerevisiae 1200 utilized 99% of the 65 g of inulin during the fermentation, and produced 20.4 and 21.0% (v/v) ethanol from chicory and dahlia inulins, respectively, within 3 days of fermentation. The maximum volumetric productivities of ethanol were 6.2 and 6.0 g/liter/h for chicory and dahlia inulins, respectively. The conversion efficiency of inulin to ethanol was 83 to 84% of the theoretical ethanol yield. Such high concentrations of ethanol were also produced from a inulin-containing agricultural crop, Jerusalem artichoke.
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