Microwave assisted alkaline deep eutectic solvents treatment inducing deconstruction of recalcitrant moso bamboo cell walls for highly efficient dual-enzymatic saccharification

Abstract

Green and efficient deconstruction and valorization of lignocellulosic biomass remain as a hot topic for biorefinery research. Herein, novel alkaline arginine-based deep eutectic solvents (DESs) pretreatment was employed to achieve efficient fractionation of highly recalcitrant moso bamboo. Higher solvent basicity was revealed for the proposed DESs with Kamlet-Taft solvatochromic parameters values of α (0.292), β (0.845), and π* (1.284). Thus, a high (β-α) value was achieved, favorable for forming stronger hydrogen bonds with lignin and xylan for subsequent separation. Supramolecular structural changes of DESs-treated bamboo cellulose were quantitatively calculated, suggesting increased crystallinity index and decreased crystallite size that were beneficial for the following enzymatic degradation. The DESs pretreatment dramatically increased the removal rate of lignin (as high as 94.4 %) and xylan (75.6 %), greatly enhancing subsequent enzymatic hydrolysis with the highest saccharification yield rate of 91.8 %, 9.8 folds as compared to that of raw bamboo biomass. Critical factors affecting enzymatic conversion performance of the bamboo cellulose were integrated, showing strong correlations with xylan removal (R 2 = 0.91), lignin removal (R 2 = 0.99), and cellulose crystallite size reduction (R 2 = 0.852). Mass balance of the present bioconversion process was performed. Based on a 100 g bamboo material balance, 51.97 g of high output fermentable sugars (including 43.96 g of glucose and 7.83 g of xylose) can be obtained after a 15-minute short pretreatment at 130 °C. Therefore, the proposed arginine-based alkaline DESs pretreatment offers new insights into the enhanced processing and bioconversion of lignocellulosic biomass.