Ionic liquid under alkaline aqueous conditions improves corncob delignification, polysaccharide recovery, enzymatic hydrolysis and ethanol fermentation

Abstract

Ionic liquids (ILs) are emerging as promising solvents for reducing the structural recalcitrance of lignocellulosic materials suitable for enzymatic saccharification. The present study investigated the use of ionic liquid [C2mim]oAc under alkaline aqueous conditions to form a system dissolving lignin selectively and to recover carbohydrate fraction of the corncob more efficiently. The optimum pretreatment condition was 120 °C, 6% ammonia, 60% ionic liquid, 15:1 liquid to solid ratio and 120 min treatment time. The results showed 68% delignification with a subsequent decrease in the crystallinity of substrate from 62% to 29%. Under optimized pretreatment conditions, the cellulose rich corncob showed 91% hydrolysability. The material balance analysis revealed the maximum sugar and ethanol production of 0.659 g/g and 0.296 g/g with 96% ILs recovery. The study showed the potential of ILs pretreatment for lignin removal of the corncob under alkaline condition which may be applicable to other lignocellulosic materials.