Systematic evaluation of polyol-assisted acidic deep eutectic solvent pretreatment for improving enzymatic hydrolysis of wheat straw

Lignocellulosic biomass has emerged as a promising renewable energy source in industrial applications; however, its robust structure requires effective pretreatment to facilitate its conversion into valuable end-products. In this work, we systematically evaluated the efficacy of polyols in enhancing acidic deep eutectic solvents (DESs) during the pretreatment and enzymatic hydrolysis of wheat straw. Our findings demonstrated that the integration of polyols, with the exception of xylitol, into choline chloride/oxalic acid (ChCl/OA) improved DES pretreatment fractionation and subsequent enzymatic digestibility, with ethylene glycol (EG) demonstrating the highest efficacy. This enhancement was confirmed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. Moreover, nuclear magnetic resonance (NMR) analysis was employed to elucidate the underlying mechanism by which the incorporation of polyols contributed to preserving the β-O-4 substructure of lignin, diminishing lignin condensation, and thereby improving enzymatic saccharification. Further optimization studies identified the optimal pretreatment conditions to be a ChCl/OA/EG molar ratio of 1:1:2, at 110 °C for 2 h. Collectively, our study not only paves the way for efficient wheat straw enzymatic hydrolysis but also offers a framework for the design and selection of DESs in the pretreatment of lignocellulosic biomass.