Ultrasonic treatment for improved solution properties of a high-molecular weight exopolysaccharide produced by a medicinal fungus

High-power ultrasound (20 kHz) was applied to modify the physicochemical properties of a high-molecular weight (MW) exopolysaccharide (EPS) from mycelial culture of a medicinal fungus. At 35 W/cm2 or higher ultrasound power, the apparent and intrinsic viscosities of EPS solution dropped by nearly 85% within 10 min, and the water solubility was increased by more than fourfold. The ultrasonic treatment led to a notable reduction of the maximum MW and a more uniform MW distribution, but no significant change in the primary structure of the EPS molecules. In contrast, the intrinsic viscosity of EPS was reduced by only 20% in 1.0 M sulfuric acid at 50 °C for 9 h. Ultrasound was proven an effective and favorable means for improving the solution properties of high-MW bioactive polysaccharides in mild conditions.