Revitalizing Multiple Bioactivities of the Lignin-Carbohydrate Complex through a Two-Step Strategy: Unraveling the Enhancement Origin from a Structural Variation Perspective

Lignin-carbohydrate complex (LCC) possesses great potential in pharmaceutical and nutraceutical fields. However, the limited bioactivities and ambiguous structure–activity relationships impede its further advances in practical applications. Here, a meticulously designed sequential two-step method, i.e., LiCl/DMSO-NaOH separation combined with enzymatic hydrolysis, was used to fabricate enzymatic LCC (ELCC) with excellent bioactivities. The antioxidant and antibacterial properties of ELCC were increased by 57 and 58% compared to those of nonenzymatic LCC and showed 49 and 46% higher than that of milled wood lignin (MWL) toward the ABTS radical and E. coil. Ultimately, ELCC also exhibited a high ultraviolet (UV)-blocking rate of 96%, outperforming both LCC (84%) and MWL (87%). The superior performance was attributed to the increased bioactive groups, mainly phenolic hydroxyl (−OH), carboxyl (−COOH), and C═C bonds, which were confirmed by revelation of the structure–activity relationships. Overall, our work demonstrated an innovative approach to revitalizing the bioactivities of LCC, prospectively boosting its practical applications in various biological fields.