Process optimization on alcohol production using sweet potato residue by simultaneous saccharification and fermentation method

To comprehensive utilize sweet potato starch industrial waste residue, simultaneous saccharification and fermentation (SSF) method was optimized to produce alcohol using sweet potato residue. Plackett-Burman design was used to select significant factors among 9 factors which had influenced on alcohol fermentation. Based on the selected results, steepest ascent method was used to approach the optimal region and response surface methodology was adopted to identify optimal values of significant factors. The results indicated that the effects of glucoamylase, inoculation ratio and fermentation temperature on alcohol fermentation was significant (P<0.05). The optimal conditions for alcohol fermentation were as follows: α-amylase 8 U/g, liquefying time 1.5 h, liquefying temperature 90℃, mass fraction of ammonium sulfate 0.15 g/100 g, pH value 4, fermentation time 36 h, glucoamylase 151 U/g, inoculation ratio 0.3% and fermentation temperature 36℃. Under the optimum conditions, alcohol concentration was 17.15%, which was close to theoretical predicted value(16.95%). The optimum technology provides reference for the alcohol production technology by SSF method for sweet potato residue.