Improving enzymatic saccharification of Chinese silvergrass by FeCl3-catalyzed γ-valerolactone/water pretreatment system

In this work, we report that FeCl3, a benign Lewis acid, could be used as a catalyst in the gamma-valerolactone (GVL)/H2O solvent system to facilitate efficient pretreatment of Chinese silvergrass. The results showed that approximately 87.8% of xylan and 75.8% of lignin were removed by 80% GVL under 170 degrees C using 50 mM FeCl3 as a catalyst. The solubilized carbohydrate fractions in the pretreatment liquor were mainly composed of monosaccharides (glucose and xylose) rather than oligosaccharides (glucose oligomers and xylose oligomers) and inhibitors (furfural, hydroxymethylfurfural, formic acid and acetic acid). Moreover, FeCl3 decreased the transesterification of GVL with hydroxyl groups on the cellulose surface and resulted in more easily degraded cellulose. Approximately 96.5% of cellulose and 92.2% of xylan in the pretreated Chinese silvergrass were converted to fermentable monosaccharides by 10 FPU/g cellulases. This study indicated that FeCl3-catalyzed GVL solvent could efficiently deconstruct biomass and increase the cellulose digestibility, which provided a novel, GVL-based pretreatment system for processing biomass. (C) 2021 Elsevier Ltd. All rights reserved.