Extracellular polysaccharide of Aspergillus flavus

Abstract

A crude extracellular polysaccharide was isolated by precipitation with ethanol from the culture medium of Aspergillus flavus, where the sole carbon source was D-galactose; purification afforded a homogeneous water-soluble polysaccharide in 0.05% yield on the weight of the employed carbon source. This polysaccharide had the relative molar weight 55 000 and [α]D22 -4.2° (c 0.5, H2O); upon total hydrolysis it afforded D-mannose and D-galactose in a 1 : 0.44 ratio. The products of hydrolysis of the methylated polysaccharide and also the course of partial acid and enzymic hydrolyses of the polysaccharide showed that the main chain was formed by (1 → 2) β-linked D-mannose units, of which each second, on average, was substituted by monomeric D-galactose units at C(6).