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

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.