Hemicellulose is an abundant group of polysaccharides found in lignocellulosic biomass, a vast resource used in applications ranging from wood products, papermaking, pharmaceuticals, and foods. The utilization of the hemicellulose fraction can be significantly improved if the relationship between their complex structure, properties and function is established. The major challenge is to uncover the link between the biophysical properties of these hemicellulose polymers with their highly variable sugar composition and complex pattern of side group decorations. Such advances are essential for understanding hemicellulose function in plants, as well as unlocking the potential for developing novel hemicellulose-based products. The main hemicellulose in softwoods is O-acetyl-galactoglucomannan (20%), followed by arabino-4-O-methylglucuronoxylan (10%), while in hardwoods, O-acetyl-4-O-methylglucuronoxylan dominates (27%). By extracting hemicellulose from spruce and birch, respectively, this work provides a detailed characterization of these polysaccharides with regards to sugar composition, molecular weight and degree of acetylation. Further, cellulose-hemicellulose hydrogels were fabricated by cultivating the cellulose producing Komagataeibacter xylinus strain ATCC® 53524 in HS medium containing dissolved hemicelluloses. Different hydrogels comprising cellulose and hemicellulose were produced, including hydrogels containing combinations of spruce hemicelluloses. These composite systems, as models of the secondary cell walls prior to lignification, were used to investigate the contributions from different wood hemicelluloses to the system’s mechanical and structural properties. Microscopy and solid-state NMR were applied to investigate the incorporation of hemicelluloses, the morphological properties of the formed network, and the nature of the interactions with cellulose. The mechanical and viscoelastic properties of the hydrogels were studied both in compression and tension to probe the distinct biomechanical roles of the different wood hemicelluloses. The diverse properties of cellulose-based composites with different hemicelluloses will be discussed with regards to their role in the cell wall of plants, as well as the implication of hemicellulose type on composite products.

Hydrogels of bacterial cellulose and wood hemicelluloses as a model of plant secondary cell walls

2019 Spring National Meeting

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