Structural and Chemical Analysis of three regions in Bamboo (Phyllostachys edulis)

Abstract

This study focuses on three different regions of moso bamboo (Phyllostachys edulis): a inner layer (IB), middle layer (MB) and outer layer (OB), to comprehensively characterize the structural features, chemical composition (ash, extractives and lignin contents) and the lignin monomeric composition as determined by analytical pyrolysis. Bamboo has a noticeable gradient anatomical pattern, with an increasing proportion of vascular bundles from IB to OB and a gradual decrease in the proportion of parenchyma tissues. In terms of chemical composition, the ash, extractives and acid-soluble lignin content gradually decrease from IB to OB. The holocellulose content follows the trend: IB (62.8%) < OB (65.9%) < MB (66.3%) while the acid-insoluble lignin content exhibits the opposite trend: IB (22.6%) > OB (17.8%) > MB (17.7%). Pyrolysis products reveal the diversity of carbohydrates and lignin derivatives, with a lignin monomeric composition rich in syringyl and guaiacyl units and lower amounts of H-units: IB has a H:G:S relation of 18:26:55, MB has 15:27:58 and OB 15:40:45; S/G ratio values were respectively 1.22, 1.46 and 0.99. A comprehensive analysis highlights significant gradient variations in the structure and chemistry of bamboo, providing robust support for the classification and refinement methods of bamboo residues for potential applications.