Enhancing enzymatic saccharification and valuable lignin recovery from wheat straw using a novel ternary deep eutectic solvent pretreatment

Green and sustainable pretreatment strategies are critical for the efficient utilization of lignocellulose. In this study, a novel ternary deep eutectic solvent (DES) consisting of choline chloride (ChCl), triethylene glycol (TEG), and oxalic acid (OA) was proposed to effectively fractionate and convert wheat straw into fermentable sugar. The ternary DES pretreatment showed remarkable pretreatment performance achieving 65.2 % delignification and 76.3 % hemicellulose removal under mild conditions. After 72 hours of enzymatic hydrolysis, a high glucose yield of 90.6 % was obtained, indicating a near-complete conversion of cellulose to monosaccharides. The structural properties of regenerated lignin samples were investigated by two-dimensional heteronuclear single-quantum coherence (2D-HSQC) and gel permeation chromatography (GPC). The regenerated lignin retained a well-preserved structure. Notably, after five recycling cycles of the DES, delignification remained at 51.2 %, with a glucose yield of 78.9 %. These findings suggest that the proposed ternary DES is a promising solvent for economically viable biomass conversion processes. • A novel ternary DES was developed to remove lignin and hemicellulose via one-pot. • The optimized DES pretreatment condition of wheat straw was at 130 ℃ for 60 min. • A high glucose yield of 90.6 % was obtained after enzymatic hydrolysis. • High amount of β-O-4 linkages and uniform molecular weight of lignin were retained.