Structural elucidation of a branch-on-branch β-glucan from Hericium erinaceus with A HPAEC-PAD-MS system

A water-soluble beta-glucan from fruiting body of Hericium erinaceus was obtained after water extraction, purification and fractionation. Analyses of monosaccharide composition, molecular weight and linkage mode demonstrated that it is a beta-glucan with 1 -> 3 and 1 -> 6 linkage modes and a molecular weight of 13.3 kDa. An endo 1,6-beta-D-glucanase was used to digest the beta-glucan and the digested products over time were analyzed with a HPAEC-PAD-MS platform. The linkage mode of each glycosidic bond in the digested oligosaccharides were confirmed with MS/MS. At the end of digestion, enzyme resistant oligosaccharides were observed as several 1 -> 6 linked glucoses with one or two 1 -> 3 linked glucose residues. All these domains are more like constructional pieces from a branch-on-branch glucan, in which multiple 1 -> 6 linked glucan chains are hooked through one or two 1 -> 3 linked glucose residues. Averagely, there is a 1 -> 3 linkage per six 1 -> 6 linked glucoses in this branch-on-branch beta-glucan.

Automated summary

The water-soluble beta-glucan extracted from the fruiting body of Hericium erinaceus has both 1→3 and 1→6 linkage modes, with approximately one 1→3 linkage per six 1→6 linked glucoses in a branch-on-branch structure. The digested oligosaccharides show enzyme resistant oligosaccharides with multiple 1→6 linked glucoses and one or two 1→3 linked glucose residues.