Structures of small oligomers liberated from barley arabinoxylans by endoxylanase from Aspergillus awamori

Abstract

Arabinoxylans consisting of more than 90% of arabinose and xylose were extracted from water-insoluble cell wall material of dehusked barley grain, and degraded with a purified endo-(1-->4)-beta-D-xylanase from Aspergillus awamori. Twelve of the oligosaccharide fragments released were isolated by a combination of size-exclusion and anion-exchange chromatography, and their structures were determined by 1H NMR spectroscopy. The oligosaccharides identified consisted of (1-->4)-linked beta-D-xylopyranosyl residues, some of which were substituted at O-2, at O-3, or at both O-2 and O-3, with alpha-L-arabinofuranosyl groups. Two new structures, a tetrasaccharide and a pentasaccharide, both containing terminal 2-O-arabinofuranosylxylopyranose as a structural element are described.