Effective Biomass Fractionation Using a Natural Acidic Polyol-Based Deep Eutectic Solvent for Sugar Recovery and...

Efficient fractionation of lignocellulosic biomass with high sugar yields and adequate lignin integrity has become a crucial challenge for biomass upgradation, especially via environmentally benign ways. Screening of a series of choline chloride (ChCl)-based ternary deep eutectic solvents (DESs) indicated that additional glycerol in acidic DESs generally promoted enzymatic hydrolysis of pretreated wheat straw. Pretreatment by a natural deep eutectic solvent (NADES) composed of ChCl, lactic acid, and glycerol performed noticeably and was examined with regard to key process factors. The pretreatment achieved 71.2% delignification, 55.3% xylan removal, and a glucose yield of 77.2% by enzymatic hydrolysis upon optimization. Structural characterization indicated modified surface morphology, increased crystallinity, disrupted lignocellulosic structures, and enlarged specific surface area. Extracted lignin exhibited a high content of β-O-4 linkages (45.3 per 100 aromatic units), suggesting its good structural integrity. Mechanisms pertaining to biomass fractionation and lignin protection were tentatively proposed. More than 80% of the DES can be recovered after five cycles while maintaining an enzymatic glucose yield above 51.0%. This work revealed the characteristics and potential of a natural acidic polyol-based DES in biomass fractionation comprised of commonly available and eco-friendly components, which may have implications in establishing an efficient and sustainable biorefinery strategy.