The alkaline extraction efficiency of bamboo cell walls is related to their structural differences on both anatomical and molecular level

• Published in: Industrial crops and products Vol. 178; p. 114628
• Main Authors: Zhu, Jiawei, Guo, Fei, Ma, Chengye, Wang, Hankun, Wen, Jialong, Yu, Yan
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2022
• Subjects: Alkaline treatment; Anatomical structure; Bamboo; Biomass recalcitrance; Hemicelluloses; Lignin; Lignin; Alkaline treatment; Hemicelluloses; Bamboo; Biomass recalcitrance; Anatomical structure
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2022.114628

Biomass recalcitrance is believed to be related to the hierarchical and heterogeneous structures of plant cell walls. In this study, the alkaline extraction efficiency of bamboo fibers and parenchyma cells is found to be highly related to their structural differences on both anatomical and molecular level. Advanced NMR spectroscopy demonstrated the lignin and hemicelluloses (mainly xylan) from fibers and parenchyma cells are significantly different in their molecular structure. The parenchyma lignin contains more β-O-4 linkages with much higher syringyl/guaicyl (S/G) ratio. By contrast, the fiber lignin contains more stable β-β and β-5 linkages as compared to parenchyma lignin. Although the hemicelluloses from both bamboo fibers and parenchyma cells shows similar molecular structure of L-arabino-4-O-methyl-D-glucurono-D-xylan, the latter contains more 4-O-methyl-α-D-glucuronic acid units. These structural discrepancies can provide explanations why the parenchyma cells have much higher “alkaline extraction efficiency” than fibers, further indicating the former is a promising feedstock in the current biorefinery scenario. Bamboo dominantly consists of stiff sclerenchyma fibers (account for 40% by volume) and soft matrix parenchyma cells (account for 52% by volume). Solution-state 2D heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) demonstrated that bamboo parenchyma cells lignin has a higher S/G ratio and more β-O-4 substructures, but lower content of β-β and β-5 linkages, which contribute to a relatively high reactivity under alkaline treatment. Bamboo parenchyma cells, with both the unconsolidated cell structure and the instable macromolecule structure, could be regarded as a highly competitive “easy bio-conversion” materials. [Display omitted] •Bamboo fibers and parenchyma cells exhibits distinct differences at both anatomical and molecular levels.•Parenchyma cells are easier to be extracted by alkali than fibers.•Lignin in parenchyma cells contained more β-O-4 linkage with higher S/G ratio.•Bamboo parenchyma cells are ideal easily-converted feedstock.