Novel ternary acidic deep eutectic solvent with high recyclability aimed at selective fractionation of lignin and fermentable sugars from bamboo

A ternary acidic deep eutectic solvent (EH/MA/PEG400 DES) was synthesized with ethylamine hydrochloride (EH), DL-malic acid (MA) and polyethylene glycol 400 (PEG400) for the pretreatment of bamboo biomass. The EH/MA/PEG400 DES possessed superior biomass pretreatment capability, resulting in the removal of 75.42 % hemicellulose and 85.30 % lignin while retaining the majority of the cellulose (87.53 %) under a relatively high solid/liquid ratio (1:7). Pretreated bamboo biomass obtained a high glucose yield of 87.38 % after 72 h of enzymatic hydrolysis. Furthermore, EH/MA/PEG400 DES exhibited exceptional recyclability, which could afford 79.34 % lignin removal and 85.29 % glucose yield even at the seventh pretreatment cycle without introducing of fresh DES. The analysis on the recovered DES revealed that the accumulation of formic acid generated from carbohydrate degradation during the pretreatment process should account for the excellent recyclability of the EH/MA/PEG400 DES. The findings in this study could offer a sustainable and efficient approach for the lignocellulosic biomass refining.