Exploration of the Linkages between Lignin and Carbohydrates in Kraft Pulp from Wheat Straw Using a C/H Isotopic Tracer.

To further our understanding of the change in association between lignin and carbohydrates after kraft pulping, isotope-labeled kraft pulp (KP) was prepared using C and D double-isotope-labeled wheat straw, and it was subjected to enzymatic hydrolysis and ionic liquid treatment to explore the linkages between lignin and carbohydrate complexes in wheat straw. Isotope abundance determination showed that C and D abundances in the experimental groups were substantially higher than those in the control group, indicating that the injected exogenous coniferin-[α-C], coniferin-[γ-C], and d-glucose-[6-D] were effectively absorbed and metabolized during wheat internode growth. Solid-state CP/MAS C-NMR spectroscopy showed that lignin was mainly linked to polysaccharides via acetal, benzyl ether, and benzyl ester bonds.