Bioethanol production from optimized pretreatment of cassava stem

The current ethanol production processes using crops such as corn and sugar cane are well established. However, the utilization of cheaper biomasses such as lignocellulose could make bioethanol more competitive with fossil fuels, without the ethical concerns associated with the use of potential food resources. A cassava stem, a lignocellulosic biomass, was pretreated using dilute acid to produce bioethanol. The pretreatment conditions were evaluated using response surface methodology (RSM). As a result, the optimal conditions were 177 °C, 10 min and 0.14 M for the temperature, reaction time and acid concentration, respectively. The enzymatic digestibility of the pretreated cassava stem was examined at various enzyme loadings (10–40 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase). With respect to economic feasibility, 20 FPU/g cellulose of cellulase and 30 CbU/g of β-glucosidase were selected for the test concentration and led to a saccharification yield of 70%. The fermentation of the hydrolyzed cassava stem using Saccharomyces cerevisiae resulted in an ethanol concentration of 7.55 g/L and a theoretical fermentation yield of 89.6%. This study made a significant contribution to the production of bioethanol from a cassava stem. Although the maximum ethanol concentration was low, an economically efficient overall process was carried out to convert a lignocellulosic biomass to bioethanol.