Response surface optimization of acid pretreatment of cassava stem for bioethanol production

Agricultural waste, cassava stem was found to contain about 25 and 40% of hemicellulose and cellulose, respectively. Bioethanol is produced from cassava stem by dilute acid pretreatment followed by alkali delignification, cellulase digestion, and fermentation by Fusarium oxysporum. Dilute acid pretreatment was optimized by response surface methodology based Box–Behnken design. The optimum xylose concentration obtained by the experiment was 11.24 g/L and the model was sulfuric acid concentration of 2.02% (v/v), solid to liquid ratio of 0.05 g/ml and 79 min. After alkali delignification and cellulase hydrolysis of pretreated cassava stem, the glucose content was 18.1 g/L and the bioethanol concentration obtained through co‐fermentation of xylose and glucose by F. oxysporum was 13.62 g/L. The optimum values indicated that 91.1% yield was achieved with cassava stem using dilute sulfuric acid pretreatment. Hence, the dilute acid pretreatment of cassava stem was found to be the promising method for bioethanol production.