Selective fractionation and valorization of maple wood using an Octadecyltrimethylammonium chloride/Ethylene glycol/Aluminum chloride ternary deep eutectic solvent

This study developed a ternary deep eutectic solvent system (Octadecyltrimethylammonium chloride/Ethylene glycol/Aluminum chloride, abbreviated as STAC/EG/AlCl 3 ) for efficient fractionation of maple wood (MP) and downstream utilization of carbohydrate-derived fractions, aiming to enhance the structural accessibility of lignocellulosic matrix through targeted deconstruction of MP, thereby enabling its value-added utilization. Under the selected pretreatment conditions (120 ℃, 30 min), the STAC/EG/AlCl 3 system effectively disrupted the recalcitrant cell wall architecture of MP, selectively removed lignin and hemicellulose, and substantially increased cellulose accessibility, increasing the enzymatic hydrolysis efficiency from 13.7 % to 92.1 %, corresponding to a 572.3 % relative increase compared with untreated MP. The treated MP was used as a substrate for simultaneous saccharification and fermentation (SSF) to produce ethanol, demonstrating the potential of the pretreated woody biomass for downstream bioethanol production. Meanwhile, hemicellulose was preferentially converted into xylo -oligosaccharides, achieving a maximum concentration of 4.46 g/L, corresponding to an apparent xylo -oligosaccharide mass yield of approximately 39.4 % based on the initial xylan. The substrate-normalized ethanol yield was 0.377 g ethanol/(g glucan + xylan in treated MP) via SSF. Structural analyses revealed substantial disruption of the biomass architecture, increased apparent cellulose crystallinity, and improved cellulose accessibility. Qualitative IGM analysis indicated noncovalent interaction regions consistent with hydrogen-bonding between the DES components and representative biomass models, providing supportive structural information for interpreting the observed fractionation behavior. Direct reuse experiments demonstrated that the DES retained partial pretreatment activity over repeated cycles. Overall, these results demonstrate the potential of the STAC/EG/AlCl 3 system for the fractionation and downstream utilization of cellulose- and hemicellulose-derived fractions.