Synergetic Dissolution of Branched Xylan and Lignin Opens the Way for Enzymatic Hydrolysis of Poplar Cell Wall

As the main hemicellulose of poplar, the interaction of xylan with lignin was expected to have profound effect on biomass recalcitrance. In this paper, the dynamic changes of xylan and lignin in poplar cell wall during a mild pretreatment using γ-valerolactone (GVL) was investigated using chemical and microscopic techniques. Synergetic dissolution of branched xylan and lignin from the secondary wall of the fiber cell was found to play a major role in opening the cell wall structure for enzymatic attack. In the case of the removal of xylan and lignin reaching a certain level, β-O-4′ cleavage of lignin which destroyed its interaction with hydrophobic cellulose face was found to make great contribution to the enhanced enzymatic hydrolysis. The deep understanding of this process could lead to a new insight into the understanding of the plant cell wall architecture and provide basic information for biomass processing.