Advanced Pretreatment Process for Enzymatic Saccharification of Rice Straw in Bioethanol Production

Lignocellulosic biomass is widely expected to be a major resource for bioethanol production but it is structurally complex and low degradable due to crystalline cellulose and amorphous hemicellulose. Hemicellulose matrices coat each fiber of cellulose microfibrils, building holocellulose structures inside and severely protected by nonbiodegradable compounds such as lignin outside. The structures are recalcitrant to enzymatic degradation, since they are rigidly packed to form a physical barrier for cellulase access to holocellulose. To digest them completely into sugars, a high dosage of expensive cellulase is required. Hence, the recalcitrance obstructs the economical production of bioethanol from lignocellulosic biomass. To overcome this problem, the pretreatment must be implemented before enzymatic digestion to alter structural integrity of biomass and also to make cellulose microfibrils and hemicellulose matrices more accessible to cellulase for conversion to sugars. In this study, we have developed the advanced pretreatment process of rice straw, i.e., delignification by chlorine dioxide, swelling and alteration of crystalline structure by sodium bicarbonate, to enable the highly efficient saccharification by enzymes (cellulase) for bioethanol production.