Meaning of xylan acetylation on xylan-cellulose interactions: A quartz crystal microbalance with dissipation (QCM-D) and molecular dynamic study.

In plant cell walls, xylan chains present various substituents including acetate groups. The influence of the acetyl substitution on the organization of xylan-cellulose complexes remains poorly understood. This work combines in vitro and in silico approaches to decipher the functional role of acetyl groups on the xylan/cellulose interaction. Acetylated xylans were extracted from apple pomace with dimethyl sulfoxide-lithium chloride (DMSO-LiCl) and deacetylated using a mild alkali treatment. The adsorption behavior of acetylated and deacetylated xylan fractions was investigated using quartz crystal microbalance with dissipation (QCM-D) and molecular dynamics. Acetylated xylans form a dense and poorly hydrated and rigid layer on cellulose with xylan chains that have two residues per helical turn conformation, whereas the deacetylated fraction forms a swollen and more viscous layer in which only the xylan chains in direct contact with the cellulose surface have two residues per helical turn conformation. The other chains have three residues per turn conformation.