Structural characteristics of lignin derived from bamboo (Melocanna baccifera)

Bamboo has long been a major raw material for the pulp and paper industry in Bangladesh; however, the structural characteristics of its lignin remain largely unexplored. This study presents the first detailed structural characterization of lignin from Bangladeshi Melocanna baccifera. Soda lignin isolated from black liquor was comprehensively analyzed and compared with native-like dioxane lignin. The empirical C₉ formulas were determined as C9H8.65O4.73(OCH₃)1.21 for dioxane lignin and C9H8.23O2.36(OCH₃)0.94 for soda lignin. FTIR and 2D HSQC NMR analyses confirmed that the lignin is composed of syringyl (S), guaiacyl (G), and p-hydroxyphenyl (H) units, characteristic of grass-type (HGS) lignin. Soda pulping significantly altered lignin structure through cleavage of α-O-4′ and β-O-4′ linkages, resulting in reduced molecular weight, decreased methoxyl content, and increased phenolic hydroxyl groups. These structural modifications enhance lignin reactivity, indicating strong potential for its utilization in biorefinery processes and the development of value-added bio-based materials.