Bioethanol production by stepwise saccharification and fermentation of sugarcane bagasse by using mild alkali pretreatment

Sugarcane bagasse, the main waste product of the sugar industry, is an important renewable biological resource owing to its wide variety of sources and high cellulose content. Based on the cellulose content analysis, sugarcane bagasse was prepared with mild alkali, followed by stepwise saccharification and fermentation, to produce bioethanol. The results of orthogonal experiments showed that enzyme dosage significantly affected enzymatic hydrolysis, where optimal conditions for hydrolysis were as follows: enzyme dosage of 25 FPU/g sugarcane bagasse, temperature of 50 , and an initial pH of 4.9. Under these optimal conditions, the enzymatic efficiency could reach up to 74.26%. Supplementation of the bagasse hydrolysate with certain nutrients facilitated yeast growth and fermentation to produce ethanol. After 96 h fermentation, the final ethanol concentration was 39.79 g/L, with a fermentation efficiency of 82.70% and an ethanol yield of 0.48 g/g. This study confirmed the feasibility of using mild alkali to pretreat bagasse hydrolysate for ethanol production by fermentation and demonstrated the benefit of pretreating sugarcane bagasse before use as raw material for ethanol production.