Structural evolution of lignin after selective oxidation of lignin-carbohydrate complex by chlorine dioxide

Lignin–carbohydrate complexes (LCCs) are important from the perspective of the anti-depolymerization barrier of lignocellulosic biomass, as it limits the high-value utilization of lignocellulosic biomass resources. In this study, the unit structure of lignin in the LCC has been investigated in depth. Oxidation of a selective lignin unit by chlorine dioxide revealed that the LCC structures are enriched with xylanase-macroporous resins, and the structure that was not oxidized in LCC was also identified. At a chlorine dioxide concentration of 90.93 mg/L, 1 g of LCC lignin is oxidized by 0.7 g chlorine dioxide. The purified residual hemicellulose lignin was mainly H-type. The β-O-4′ signal was the strongest for the bond between lignin and carbohydrates. Therefore, it is speculated that most of the residual lignin in bamboo-alkali hemicellulose exists in the form of non-phenolic structural units. This study provides a reference for further studies on the specific structures of LCC.