Evidence for differential interaction mechanism of plant cell wall matrix polysaccharides in hierarchically-structured bacterial cellulose

The interaction mechanism of two plant cell wall polysaccharides, arabinoxylan and xyloglucan, with cellulose has been investigated by means of bacterial cellulose fermentation to mimic the cell wall biosynthesis process. The combination of small angle scattering techniques with XRD and SEM has enabled the identification of different structural features comprising hierarchically-assembled bacterial cellulose, i.e. cellulose microfibrils and ribbons. The SANS results have been described by a core–shell formalism, which accounts for the presence of regions with different solvent accessibility and supports the existence of microfibril sub-structure within the ribbons. Additionally, SAXS and XRD results suggest that the microfibril packing and crystalline structure are not affected by arabinoxylan, while xyloglucan interferes with the crystallization and assembly processes, resulting in less crystalline I_β-rich microfibrils. This specific interaction mechanism is therefore crucial for the cellulose microfibril cross-linking effect of xyloglucan in plant cell walls. It is proposed that the distinct interaction mechanisms identified have their origin in the differential structural role of arabinoxylan and xyloglucan in plant cell walls.