High-efficient fractionation of poplar chips by ternary deep eutectic solvents system for elevating enzymatic hydrolysis

The traditional acid-based binary deep eutectic solvents (DESs) have the disadvantages of relatively low separation efficiency and relatively serious damage to lignin structure. In this study, salicylic acid, as the third component, was introduced into DESs fractionation system, and the effect of ternary DESs (t-DESs) on biomass separation and subsequent enzymatic hydrolysis was studied. After t-DESs fractionation, the separation efficiency for the components of lignocellulosic biomass was obviously improved, which the cellulose purity of residual substrate reaching 84.17 %, and the removal of hemicelluloses and lignin reaching 91.2 % and 75.3 % respectively. Compared to the DES fractionation without salicylic acid, the t-DES fractionation reserved more linkage bonds in lignin structure, including βO4, β5, and ββ. Especially, 28.3 % of the βO4 substructure was remained in t-DES lignin, while that of the DES fractionation without salicylic acid only reached 22.5 %. The enzymatic conversion of the substrate by t-DESs at 110 ℃ reached 82.7 %.