Pretreatment of biomass with ethanol/deep eutectic solvent towards higher component recovery and obtaining lignin with high β-O-4 content

Deep eutectic solvent (DES) is an ideal solvent for extracting lignin in biomass pretreatment process. However, excessive breakage of the β-O-4 bonds of lignin remained a challenge for DES-pretreated biomass. In this study, a novel pretreatment system of choline chloride-citrate acid DES combined with ethanol for the pretreatment of bamboo was developed. The chemical characteristics of extracted lignin of bamboo before and after pretreatment were analyzed by gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR). The results showed that the lignin extracted by ethanol/DES had moderate and uniform molecular weight (M