Evaluation of Bioethanol Production from Sweet Potato at Low-temperature Hydrolysis with Conventional Amylolytic Enzymes Simultaneous with Fermentation

The biorefinery using wasted sweet potatoes is an attractive way to replace fossil fuels and integrate other products. This work aimed to produce sweet potato ethanol using conventional commercial amylolytic enzymes usually applied at 60-90 & DEG;C, but at a low temperature (28-42 & DEG;C). Additionally, simultaneous hydrolysis and fermentation were performed. Enzyme concentration in the hydrolysis, temperature, time, and concentration of the potassium metabisulfite solution in the fermentation yield was also studied through central composite design (CCD). Moreover, the effect of alpha-amylase addition before and after (before cooling) the pretreatment of sweet potato was evaluated. The sweet potato was characterized by moisture and total reducing sugars. When the enzymes are added simultaneously, the optimal conditions are 35 & DEG;C and 25.1 h for a minimum yield of 75 %. When alpha-amylase is added just after heating, the yield is 79.7 % in only 22 h of incubation, achieving a gain of 8.6 h. Thus, this work shows that it is possible to use enzymes generally used at higher temperatures at lower temperatures, which can help reduce the energy costs of sweet potato ethanol production.