Coupling deep eutectic solvent and laccase treatment for cellulose fiber recovery from lignocellulosic biomass

Effective pretreatment is critical for recovering high-purity cellulose fiber from lignocellulosic biomass. This study reports a sequential biochemical strategy for wheat straw valorization employing choline chloride/lactic acid/water natural deep eutectic solvent (DES) followed by laccase treatment. This integrated approach synergistically targeted lignin and hemicellulose removal, and facilitated the recovery of highly crystalline cellulose fibers. The DES solution consists of chloride (ChCl) and lactic acid (LA) (1:9 molar ratio), containing 10% (w/w) water. Optimization revealed that DES pretreatment (120 °C, 2 h) coupled with laccase treatment (35 °C, 24 h) maximized delignification (99.5%) and hemicellulose removal (95.5%), and yielded 95.1% remaining cellulose with 93.5% purity. This approach realized that both retention and purity of cellulose reached over 90%, which cannot be achieved by majority pretreatment methods. Comprehensive physicochemical characterization (SEM, FTIR, XRD, TGA) demonstrated that the recovered cellulose fibers possess significantly enhanced crystallinity and superior thermal stability compared to the untreated biomass. This study provides a novel approach which integrating DES-laccase treatment process to recover high-purity cellulose fibers with negligible cellulose loss.