Deacetylation of Xylan Affects Lignin Properties of Aspen Wood

Lignocellulose from hardwood species is a good source of sugars for biofuels. However, extensive acetylation of hardwood xylan impedes lignocellulose saccharification by blocking xylan hydrolysis and causing inhibitory acetic acid during fermentation. The team of Xiaoyu Zhu and Yan Zhou from Chinese Academy of Sciences aimed to improve aspen saccharification through the introduction of the acetyl xylan esterase AnAXE1 from Aspergillus niger into aspen, to facilitate deacetylation of xylan.

AnAXE1-expressing plants exhibited reduced xylan acetylation and grew normally. Without pretreatment, their lignocellulose yielded 25% more glucose per unit mass of wood than wildtype plants. After acid pretreatment, glucose yields still slightly improved. Further analysis revealed that AnAXE1 expression in aspen also reduced the molecular weight of xylan and xylan–lignin complexes, increased cellulose crystallinity, altered the lignin composition, and increased lignin solubility in dioxane and hot water.

This study revealed several changes in plant cell walls caused by deacetylation of xylan. Deacetylating xylan not only increased its susceptibility to hydrolytic enzymes but also changes the cell wall architecture, increasing the extractability of lignin and xylan and aiding saccharification.