Extrusion process to enhance the pretreatment effect of ionic liquid for improving enzymatic hydrolysis of lignocellulosic biomass

Abstract

Extrusion process using 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) in co-solvent, dimethyl sulfoxide (DMSO), was conducted to improve the pretreatment effect on the enzymatic saccharification of pussy willow (Salix gracilistyla Miq.). The use of a twin screw extruder capable of continuous processing increased the solid loading to 50% in [EMIM]Ac and its co-solvent DMSO. The water-soluble fraction was increased by increasing the [EMIM]Ac amount in co-solvent and the extrusion temperature but decreasing the screw rotating speed and solid loading. The surface morphologies of the extruded product showed remarkable disruption of the cell wall structures and fibrillation with increasing amounts of [EMIM]Ac in co-solvent. With increasing [EMIM]Ac amount in co-solvent and extrusion temperature and with decreasing screw rotating speed and solid loading, the crystalline structure of cellulose was more disrupted, resulting in the increase in saccharification yield. The highest yield of glucose and xylose was 99.0% and 99.5%, respectively, from the pretreated products using only [EMIM]Ac under solid loading of 15% at 160 °C extrusion temperature and 5 rpm screw rotating speed. The initial saccharification rate was faster in the pretreated product precipitated in alcohol and acetone than in water.