Glucuronoxylan

Glucuronoxylan is a major type of xylan, a hemicellulose component of plant cell walls. It features a β-1,4-linked backbone of D-xylose units, to which predominantly α-D-glucuronic acid residues are attached as side chains. In many woody plants these glucuronic acid units are 4-O-methylated (MeGlcA). The pattern and extent of substitution vary by species, with hardwoods typically richer in MeGlcA than softwoods. Acetyl groups may also decorate the xylosyl backbone in some species.

Glucuronoxylan is abundant in hardwoods and in some grasses and cereals. The side chains influence the physical properties of the cell wall by modulating interactions with cellulose and lignin, and by affecting wall porosity and recalcitrance. MeGlcA residues can participate in lignin–carbohydrate complexes, contributing to cross-linking within the wall and impacting chemical pulping and enzymatic accessibility.

Industrial and research interest centers on its extraction and breakdown. Glucuronoxylan is typically solubilized under alkaline conditions during pulping and pre-treatment processes. Characterization relies on sugar composition analyses, linkage analysis, NMR, and mass spectrometry. Enzymatic deconstruction uses xylanases to cut the backbone and specific glucuronidases to remove glucuronic acid side chains, though substitutions can hinder hydrolysis.

Applications include production of xylooligosaccharides and refinement of biomass into fermentable sugars for biofuels. Knowledge of substitution patterns aids in predicting processing behavior and the design of enzyme cocktails for efficient saccharification. Glucuronoxylans also serve as a model for studying lignin–carbohydrate interactions in plant cell walls.