Ethanol production from sweet potato tubers by applying enzyme preparations (Department of Agricultural Chemistry)

甘藷芋(100kg)を酵素剤で処理し, 150l容発酵槽を用いて発酵を行ないエタノール生産について検討した。芋の磨砕物にペクチナーゼ(100g)を加えて処理(pH4.5,25℃, 18時間)することにより液状化を図った。澱粉の糊化と液化を図るために, 液状化物にα-アミラーゼ(50g)を加えて加熱処理(pH5.5,80℃, 10分間)を行った。加熱処理することにより澱粉の糖化が容易となり, 液状化物の粘度も低下した。加熱処理して得た液化物はグルコアミラーゼ(100g)で処理(pH45,40℃, 4時間)することにより糖化された。糖化物に栄養源と乾燥パン酵母(400g)を加えてpH4.5,30℃でエタノール発酵を行った。発酵30時間でエタノール濃度16.5%の発酵液が得られ, 発酵歩合は82%であった。発酵過程で6.6m^3の炭酸ガスが発生した。発酵液を単式蒸留装置で蒸留することにより, 50%エタノール溶液30lが得られた。The batch production of ethanol from sweet potato tubers (100kg) by applying commercial enzyme preparations in a 150-L fermentor was investigated. The minced tubers were macerated with pectinase (0.1%, w/w) for 17hr at 25℃ and pH4.5. The macerated mash (pH5.5) was heated to dextrinize and liquefy starch with α-amylase (0.05%, w/w) for 10min at 80℃. The heat-treatment of the mash was useful to facilitate saccharification of starch and to reduce the viscosity. For saccharification, the heat-treated mash (pH4.5) was treated with glucoamylase (0.1%, w/w) for 4hr at 40℃. The saccharified mash was supplemented with nutrients and inoculated with dried baker's yeast (0.4%, w/w) for ethanol fermentation at 30℃. After 30hr fermentation, the ethanol yield of 16.5% (v/v) was achieved and the fermentation efficiency was 82%. During the fermentation, the total carbon dioxide evolved was 6.6m^3. The fermented mash was distilled to produce 50% ethanol (30L) and stillage by using a distillation apparatus