Hemicelluloses as recalcitrant components for saccharification in wood

Abstract

Cellulose is a linear polymer consisting of more than 2,000 1,4-β-glucopyranosyl residues. The glucosyl residues form intramolecular hydrogen bonds at O3-O5′ and O6-O2′. Therefore, each glucosyl residue is bound to its neighbors by three bonds consisting of one covalent bond at C1β-C4′ and two hydrogen bonds at O3-O5′ and O6-O2′. Each glucosyl residue is oriented at an angle of 180° to the next residue of the chain, which might be synthesized from two residues at a time during cellulose biosynthesis. Since individual strands of cellulose are intrinsically less hydrophilic than other soluble polysaccharides, crystals tend to form with extensive intra- and intermolecular hydrogen bonds and complex, three-dimensional structures. In these crystals, each parallel glucan strand is situated between hydrophobic ribbon faces by both hydrophobic bonds and intermolecular hydrogen bonds (O6-O3′). Glucan forms a nanofiber, which associates to form bundles of compact lattices made up of hydrophobic and hydrogen bonds. In the natural crystals (cellulose I), the cellulose strands are parallel and form monoclinic cellulose I (Iβ) (Hackney et al.1994). © 2011 Springer Science+Business Media, LLC.