Sweet potato (Ipomoea batatas) was a wildely planted root crop in most area of China and considered as a good feedstock for fuel ethanol production. Very high gravity ethanol fermentation technology exhibited promising industrial application for advantages including productivity improvement, polluted water output reduction and energy consumption saving. In this study very high gravity liquefied sweet potato mash containing 260 g/kg glucose (after fully saccharified) was used for fuel ethanol fermentation. 0.8 g/kg (dry matter weight) was proved as the optimum glucoamylase adding dosage in simultaneous saccharification and fermentation. Datas analysis indicated that the osmotic pressure was controlled strictly exhibited by high growth rate of yeast and high rate of ethanol formation comparing with other dosages, and 119.78 g/kg (15.07 %, v/v) ethanol equivalent to 90.16 % of theoretical yield was achieved in 64 hours.
