Exploration of biomass fractionation and lignin removal for enhancing enzymatic digestion of wheat-stalk through deep eutectic solvent Cetyl trimethyl ammonium chloride:Lactic acid treatment

The cationic surfactant-based deep eutectic solvents (DESs) have attracted extensive attention due to their effectual destruction of the natural anti-degradation barrier structure in lignocellulose. In this research, functional DES Cetyl trimethyl ammonium chloride:Lactic acid (CTAC:LA molar ratio 1:0.5 to 1:6) was fabricated for pretreating wheat-stalk. The relationships of accessibility, lignin removal, xylan separation, and enzymolysis efficiency were explored. The highest delignification (88.3 %) and xylan removal (89.0 %) were obtained through the treatment with CTAC:LA (1:4, mol/mol, 160 °C, 60 min), acquiring 86.8 % of enzymolysis efficiency. The structure of CTAC:LA-treated wheat-stalk was changed to porous state, while the accessibility and crystallinity were substantially improved to 668.2 mg/g and 57.6 %, respectively. The lignin surface area declined from 672.7 to 335.4 m 2 /g. Furthermore, the structure of lignin disrupted by CTAC:LA was analyzed by 2D-HSQC NMR, implying that CTAC:LA could cleave the C O covalent bond and C C bond and degrade the S- and H-units in wheat-stalk lignin through interaction. The potential pretreatment mechanism was proposed through comprehensive exploration at the molecular level and macro level, and this built pretreatment process held great promise for valorizing biomass into highly valuable chemicals.