γ-Valerolactone/CuCl2 biphasic system for high total monosaccharides recovery from pretreatment and enzymatic hydrolysis processes of eucalyptus

The efficient fractionation and recovery of monosaccharides (xylose and glucose) from lignocellulosic biomass facilitates subsequent sugar-based derivative production. This study introduces a one-pot γ-valerolactone/ CuCl₂ biphasic pretreatment system (100-mmol·L^-1 CuCl₂, 180 °C, 60 min) capable of achieving removal rates of 92.25% and 90.64% for xylan and lignin, respectively, while retaining 83.88% of cellulose. Compared to other metal chlorides (NaCl, LiCl, FeCl₃, and AlCl₃), the γ-valerolactone/CuCl₂ system recovered 121.2 mg·(g eucalyptus)^-1 of xylose and 55.96 mg·(g eucalyptus)^-1 of glucose during the pretreatment stage and 339.2 mg·(g eucalyptus)^-1 of glucose during the enzymatic hydrolysis stage (90.78% of glucose yield), achieving a total monosaccharide recovery of 86.31%. In addition, the recovery of γ-valerolactone was 79.33%, exhibiting minimal changes relative to the pretreatment performance. The method proposed in this study allows a high total monosaccharides recovery and a circular economy-oriented pretreatment approach, offering a viable pathway for biorefinery.