Bio-based deep eutectic solvent of enhanced lignin solubility for wheat straw fractionation and full-component utilization

Abstract

Balancing efficient fractionation with the structural intactness of lignin in lignocellulose pretreatment remains challenging. An innovative strategy with selective lignin solubilization/extraction/stabilization was developed to efficiently fractionate high-quality carbohydrates and well-preserve lignin from wheat straw employing a bio-based ternary deep eutectic solvent comprising dimethyl isosorbide/ethylene glycol/oxalic acid. Ultrahigh pretreatment efficiency (90.7 %), delignification rate (92.2 %), and cellulose recovery (88.4 %) were demonstrated in 37 min. Furthermore, excellent enzymatic digestibility (91.9 %), conversion of inhibitor-free carbohydrate hydrolysates to microbial lipid (8.3 g/100.0 g wheat straw), and lignin with good UV-blocking performance were obtained. The mechanistic insights into delignification were elucidated through Hansen solubility theory, revealing that the lower relative energy difference, strong hydrogen bonding cohesion, and ethylene glycol incorporation enabled efficient utilization of the sugar platform without compromising the structural intactness of lignin. This lignin solubilization-oriented strategy complements green and efficient pretreatment methods for lignocellulose that target holistic valorization and contribute to closed-loop biorefineries.