Effect of xyloglucan molar mass on its assembly onto the cellulose surface and its enzymatic susceptibility

Xyloglucan from tamarind seed has been submitted to an ultrasound treatment that reduces its molecular size to investigate the impact of molar mass on the interaction with cellulose. A low molar mass xyloglucan fraction (XGu, 1.04×10⁵gmol^-1) was purified and its adsorption on the cellulose nanocrystal (CNC) surface has been investigated comparatively to the native fraction that presents high molar mass (XGn, 10.28×10⁵gmol^-1). XGn arranged as loops and tails on CNCs whereas XGu formed trains onto the cellulose surface. Despite the extended conformation, XGu is able to cross-link cellulose nanocrystals in the layer-by-layer CNC-XG-CNC assemblies. Hydrolysis of model films by a xyloglucan-specific endoglucanase confirmed the greater accessibility of XGn loops and tails compared to the XGu trains. More importantly, in situ ellipsometry revealed that the presence of loops and tails facilitated swelling of CNC layers linked by XGn whereas the CNC-XGu-CNC structure did not experience swelling.