Isolation and physicochemical characterization of soluble scleroglucan from Sclerotium rolfsii. Rheological properties, molecular weight and conformational characteristics

Scleroglucan produced by Sclerotium rolfsii ATCC 201126 exhibited pseudoplastic behaviour and an exponential relationship between apparent viscosity and polymer concentration. Viscosity showed strong heat-stability (100°C/60 min). Tolerance up to 20% w/v NaCl and over a wide pH range (0¯13) was also found. A sharp decrease on viscosity at NaOH concentrations higher than 0.15 M was observed due to dissociation of the triple-helix. According to intrinsic viscosity determinations and gel filtration chromatography on Sepharose CL-4B, the weight-average molecular weight of native polysaccharide was about 5×106 Da for the triplex and 1.6×106 Da for the random coil. These values, in addition to the change in complexation with Congo Red, support the idea of the triple-helical conformation in neutral or slightly alkaline solutions (<0.15 M NaOH), and single chains in a highly alkaline environments.