Enzyme is a key factor to produce fermentable sugar for subsequent fermentation to occur. The curve lines in Fig. 4 show similar production rate of bioethanol in the first 100 min of fermentation but bioethanol yield were lower for enzyme concentration at 15 units/mL and 30 units/mL. Amyglucosidase is the enzyme used as catalyst in this SSF process to convert starch to glucose, with supplier proposed working concentration of 60 units of activity per mililiter at pH 4.5 and 55 C. Although the enzymatic working environment is not at its optimum as suggested by supplier, enzyme activity did not significantly affected by the investigated condition. As can be seen from Fig. 4, most of the bioethanol yields exceed 90%, averaging at 7.0 g/L of bioethanol concentration for enzyme concentration at 45 units/mL and above. In fact, if more enzyme was used, the saccharification rate would be higher and thus higher ethanol production rate as well (Choi et al., 2010). However, lower usage of enzyme is preferable in order to minimize cost and 45 units/ml of enzyme was chosen where 94.98% yield of ethanol was obtained which is equivalent to 7.17 g/L of bioethanol production. A concentration beyond 45 units/ml of enzyme would not greatly affect the bioethanol yield