Formation and Structure of Extracellular Glucans Produced by Claviceps Species

Abstract

SUMMARY: Submerged cultures of Claviceps fusiformis (Loveless) became progressively viscous during the incubation because of the production of an extracellular polysaccharide. The polysaccharide was shown to be a branched glucan with a β1 → 3 linked main chain having single glucopyranosyl units at intervals along it in the β1 → 6 configuration. For most of the media investigated growth at 27° and between pH 5 and 6 was accompanied by glucan production, which ceased when growth was arrested by lack of nutrient. The glucan was re-metabolized by the fungus only to a limited extent as the culture aged; the degree of branching varied during the culture period. The unit amount of glucan synthesized was not affected by numerous successive subculturings over a period of several months, but the product from the later cultures had a greater degree of branching. Branched glucans of similar structure to the above were also detected in low concentration in the natural sclerotia. The presence of β1 → 3 linked glucans in the cell walls of this and other fungal strains examined was also indicated.