The effect of bamboo (Phyllostachys pubescens) cell types on the structure of hemicelluloses

Abstract

Bamboo ( Phyllostachys pubescens ) is a promising high-performance material because of its large planting areas, fast growth, good adaptability, high ultimate strength and stiffness. Hemicelluloses in bamboo have been focused and studied, however, less effort has been dedicated to study on the components, distributions and structures of hemicelluloses in different cells for explaining the mechanism of bamboo growth. Here, we obtained dimethyl sulfoxide (DMSO)-soluble and alkali (NaOH)-soluble hemicelluloses from bamboo fibers (BF) and parenchyma cells (PC), which were separated from bamboo ( Phyllostachys pubescens ) by their density difference. Molecular weight analysis revealed that the molecular weights of DMSO-soluble and alkali-soluble hemicelluloses isolated from PC were higher than those isolated from BF. Chemical compositions and cell morphology was characterized by field emission scanning electron microscope (FE-SEM), high-performance anion exchange chromatography (HPAEC), and confocal Raman microscope (CRM). The results showed that the content of cellulose (36.32 %) was higher in BF with thicker wall, while the content of lignin and hemicelluloses (36.33 % and 19.39 %, respectively) was higher in PC with thinner wall. The Fourier transform infrared (FT-IR) spectra and nuclear magnetic resonance (NMR) technique analyses indicated that bamboo hemicelluloses were composed of O -acetyl- α - L -arabino-4- O -methylglucurono- β -(1→4)- D -xylan and β -(1→3) (1→4)-glucan. 1 H NMR showed that the acetylation degree of H D -Fiber (0.069) was lower than that of H D -Parenchyma (0.127). Particularly, the hemicelluloses isolated from BF were acetylated only on C3 position, while hemicelluloses isolated from PC were acetylated both on C2 and C3 positions. This work presents a novel understanding about hemicelluloses structures of different cell types in bamboo and holds promises for the high-value added utilization of bamboo in the fields of food-related productions and biorefinery. • Hemicelluloses isolated from bamboo fibers and parenchyma cells were firstly investigated. • Hemicelluloses from parenchyma cells were acetylated on C2 and C3 position. • Hemicelluloses from bamboo fibers were acetylated only on C3 position. • The major structure of hemicelluloses is O -acetyl- α - L -arabino-4- O -methylglucurono-(1→4)- β - D -xylan. • The second major structure of hemicelluloses is β -(1→3) (1→4)-glucan.