Structural characterization of Botryosphaeran: a (1→3;1→6)-β-d-glucan produced by the ascomyceteous fungus, Botryosphaeria sp.

The exopolysaccharide, Botryosphaeran, produced by the ligninolytic, ascomyceteous fungus Botryosphaeria sp., was isolated from the extracellular fluid by precipitation with ethanol, and purified by gel permeation chromatography to yield a carbohydrate-rich fraction (96%) composed mainly of glucose (98%). Infra-red and 13C NMR spectroscopy showed that all the glucosidic linkages were in the β-configuration. Data from methylation analysis and Smith degradation indicated that Botryosphaeran was a (1→3)-β-d-glucan with approx 22% side branching at C-6. The products obtained from partial acid hydrolysis demonstrated that the side branches consisted of single (1→6)-β-linked glucosyl, and (1→6)-β-linked gentiobiosyl residues.