Improved high-solid loading enzymatic hydrolysis of steam exploded corn stalk using rapid room temperature γ-valerolactone delignification

Abstract

The present work proposes a novel combined pretreatment coupling steam explosion and room temperature γ-valerolactone (GVL)/water delignification without addition of any acid/ alkali catalysts to improve enzymatic saccharification of corn stalk. Up to 70 % of original xylan was dissociated from corn stalk after steam explosion at 1.5 MPa (198 °C) for 10 min with over 92 % of glucan retained. The subsequent delignification using green GVL/water solvent at room temperature for 0.5 h removed 70.8 % of lignin, producing a glucan-enriched solid (68 %, w/w). The effective delignification is mainly attributed to the substantial destruction of compact lignocellulosic matrix and the excellent lignin solubility in GVL/water. Over 80 g/L of glucose concentration was obtained when the pretreated solid was subjected to high-solid loading enzymatic hydrolysis (20 %) with relatively low cellulase addition [15 filter paper cellulase units (FPU)/g glucan], which was much higher than that treated with only steam explosion (44.26 g/L). Consequently, the combined pretreatment is found to be effective to fractionate corn stalk and produce a glucan-enriched solid that exhibits significantly enhanced enzymatic digestibility under high-solid loading and relatively low cellulase addition, thus providing a promising option for green lignocellulosic biorefinery.