Co-production of xylo-oligosaccharides and glucose via alkaline amino acid deep eutectic solvent pretreatment coupled with stepwise enzymatic hydrolysis

Green and efficient valorization of lignocellulosic biomass is pivotal to realizing sustainable biorefineries for a circular bioeconomy. Herein, an alkaline amino acid deep eutectic solvent (DES) pretreatment coupled with stepwise enzymatic hydrolysis was developed to improve selective delignification and facilitate co-production of xylo-oligosaccharides (XOS) and glucose. The aqueous choline hydroxide-arginine (ChOH-arginine) system enabled selective lignin removal while preserving hemicellulose for subsequent XOS production. Under mild conditions (80 °C, 30 min), a delignification rate of 84.25% was achieved, along with high retention of xylan (>71%) and cellulose (>86%). Density functional theory (DFT) calculations were performed to elucidate the underlying mechanism of lignin dissolution. Furthermore, the two-step xylanase-cellulase hydrolysis strategy delivered excellent XOS production performance. Critically, the pretreatment selectively cleaved lignin-carbohydrate ester linkages, suppressed lignin condensation, and retained a high β-O-4 linkage content, which are beneficial for the downstream valorization of lignin. Overall, this work proposes an integrated and sustainable strategy for efficient bioconversion of corn stover.