Fractional extraction and structural characterization of hemicelluloses from wheat straw

Abstract

The chemical composition of 7 hemicellulosic fractions extracted directly from dewaxed wheat straw with sodium hydroxide at sequentially increasing strength from 0.125 to 1.50 M are reported. The structural features of the fraction 3 were evaluated by means of methylation analysis and 13C-NMR spectroscopy. The hemicelluloses were confirmed to be a β-(1-4)-xylan with side chains consisting of L-arabinofuranosyl and D-xylopyranosyl groups attached in position 3, and D-glucopyranosyluronic acid or 4-O-methyl-D-glucopyranosyluronic acid group attached at position 2. For every 15 D-xylopyranosyl residues in the main chain, there was one L-arabinofuranosyl group. For 19 such D-xylopyranosyl residues, there was one D-xylopyranosyl group, and for ∼26 such D-xylopyranosyl residues, there was one uronic acid unit.