Highly-efficient pretreatment using alkaline enhanced aqueous deep eutectic solvent to unlock poplar for high yield of fermentable sugars: Synergistic removal of lignin and mannan

Herein, a short-time alkaline enhanced aqueous DES (AaDES) pretreatment using choline chloride/ethylene glycol was reported, aiming at enhancing cellulose and xylan enzymatic digestibility. Simultaneously, saccharification efficiency of cellulose and xylan was reached to 91.2% and 99.0%, respectively, ∼4 and ∼ 24 times that of raw poplar. Pretreatment time was substantially shortened from 15-24 h to 4 h. Notably, 43.00 kg fermentable sugars (73% of the theoretical maximum) and 12.98 kg lignin with rich β-O-4' linkages were obtained based on 100 kg poplar. The complete removal of acetyl and partial removal of lignin and mannan contributed to excellent pretreatment performance. It was found that enzymatic digestibility of xylan/cellulose was positively correlated with removal of mannan (R2 = 0.9719; R2 = 0.9010) and delignification (R2 = 0.6888; R2 = 0.8293). Drastic reduction in pretreatment time along with high-yield sugars in AaDES system will provide strength towards industrial level biorefinery.