STRUCTURAL-ANALYSIS AND RHEOLOGICAL BEHAVIOR OF AN EXTRACELLULAR POLYSACCHARIDE FROM DRECHSLERA-SPICIFERA

The fungus Drechslera spicifera produces a high viscosity extracellular glucan polymer in Galzy and Slonimski medium containing glucose. This polysaccharide submitted to methylation study, Smith degradation and enzymic hydrolysis was concluded to be composed of a backbone of beta (1 --> 3)-linked D-glucopyranosyl residues and possessed two single branches of a beta-D-glucopyranosyl residue joined through C-6 for every five D-glucopyranosyl residues of the backbone as lentinan from Lentinus edodes. In water solution, this polysaccharide developed a high viscosity. ten times the viscosity of scleroglucan, and showed good thermal stability. Its behaviour was investigated as a function of the sodium hydroxide concentration. At low NaOH concentration the viscosity rises, due to an increase in solubility and probably to interchain interactions with proteins. When the NaOH concentration increased. there was a rapid and irreversible decrease in the viscosity attributed to a conformational transition.