Role of O-acetyl galactoglucomannan in softwood lignification.

Glucuronoxylan and (galacto)glucomannan are the major hemicelluloses in hardwoods and softwoods, respectively, and are acetylated in their native states. The important role of partially acetylated xylan in hardwood lignification has previously been elucidated using a quartz crystal microbalance with dissipation. This study aims to investigate the role of O-acetyl galactoglucomannan (Ac-GGM) in the lignification of softwoods. The acetyl groups were found to decrease the adsorption of GGM onto cellulose. In addition, these acetyl groups also reduced the formation of dehydrogenation polymer (DHP). These findings suggest that the acetyl groups in Ac-GGM inhibit both GGM adsorption on cellulose and DHP formation. The amount of DHP formed on the cellulose/Ac-GGM/xylan (XY) matrix was comparable to that on the cellulose/XY matrix, despite the XY content being significantly lower in the former than that in the latter. This observation suggests that XY provides polymerization sites for monolignol coupling, while Ac-GGM facilitates the deposition of XY on the surface of the polysaccharide matrix.