Hemicellulose is an amorphous and variable structure formed of
heteropolymers including hexoses (D-glucose, D-galactose and
D-mannose) as well as pentose (D-xylose andL-arabinose) and may
contain sugar acids (uronic acids) namely,D-glucuronic,D-galacturonic and methylgalacturonic acids[69,70]. Its backbone chain is
primarily composed of xylanb(1/4)-linkages that includeD-xylose
(nearly 90%) and L-arabinose (approximately 10%) [67].Branch
frequencies vary depending on the nature and the source of feedstocks. The hemicelluloses of softwood are typically glucomannans
while hardwood hemicellulose is more frequently composed of
xylans [69]. Although the most abundant component in hemicellulose, xylan composition still varies in each feedstock [71].
Because of the diversity of its sugars, hemicellulose requires a wide
range of enzymes to be completely hydrolyzed into free monomers
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