Optimization of high-gravity fermentation conditions for ethanol production from cassava

The cassava was used as substrate for alcohol production by high-gravity fermentation. Based on the optimization of liquefaction and sac- charification conditions, the effects of medium components, temperature and pH on fermentation were analyzed. The results showed that when the al- cohol fermentation of cassava was conducted under optimal liquefaction and saccharification conditions, the optimum concentrations of nitrogen sources and inorganic salts were as follows: 0.25% urea (w/w), 0.45 g/L MgSO4·7H2O, 1.50 g/L KH2PO4, 0.20g/L CaCl2. Besides, the opti- mal fermentation temperature was 33℃, the optimal initial pH was 4.5, the inoculum of yeast was 10% (v/v), and the fermentation time was 48 h. Un- der above conditions, the alcohol concentration of mature mashing reached 17.2% (v/v), while the conversion rate of starch was 91%.