Structural characterization of water soluble β-glucan of oat bran

Abstract β-glucan was isolated from oat bran in a highly purified form. The bran was characterized for its contents of dietary fiber, β-glucan, fat and protein. The isolated β-glucan was free of protein and contained only glucose in GC sugar analysis. Two types of β-glucan were obtained with different solubilities. Their molar masses were 1.6 million for the less soluble and 1.1 million for the more readily soluble type. No structural differences were found. The two-dimensional correlation NMR spectrum of the isolated β-glucan showed that the glucose units are joined with 1,3- and 1,4-linkages only. The oligosaccharides produced by the action of a specific enzyme, lichenase, were analyzed by HPLC and capillary zone electrophoresis. The major products are 3 2 -β- d -glucosyl cellobiose (trisaccharide) and 3 3 -β- d -glucosyl cellotriose (tetrasaccharide), which account for 95% of the whole. Also, 3 4 -β- d -glucosyl cellotetraose (pentasaccharide) and other oligosaccharides with degree of polymerization (DP) higher than 5 were detected as minor components.