Sustainable production of fermentable sugars and antioxidant lignin from industrial xylose residue with facile deep eutectic solvents

This study presents a readily synthesized deep eutectic solvent composed of guanidinium hydrochloride and lactic acid (GH/LA) for refining various industrial xylose residues (delignification and non-delignification), addressing industrial challenges caused by the accumulation of residues. Under mild conditions (120 °C for 2 h), lignin was efficiently extracted, leaving cellulose intact in the solid fraction. The isolated cellulose exhibited a theoretical sugar yield of 100 % within 48 h, which was attributed to the optimal lignin content (6.15 %) remaining in the cellulose residue. The recovered lignin demonstrated high purity (93.36–97.95 %), low molecular weight (2786–3089 g/mol), moderate polydispersity (2.29–2.37), remarkable thermal stability, and potent antioxidant activity (IC 50 =1.25 mg/mL). Comprehensive analysis confirms GH/LA DES pretreatment as a simple and effective method for efficient industrial waste utilization.