Molecular weight determination
The molecular weight of the samples was determined by high-performance liquid chromatography (HPLC) and gel permeation chromatography (GPC). Dextran standards and 10 mg/mL of samples were dissolved in 0.7% sodium sulfate solution, and analyzed by a LC-2030C3D series HPLC (Shimadzu, Japan) system equipped with RID 20 and sepexsrtsec-100 column (7.8 × 300 mm, 5 μm) to determine the retention time. The column was maintained at 35 °C with 0.7% sodium sulfate solution as the mobile phase at a flow rate of 0.5 mL/min and an injection volume of 10 μL. The molecular weight of the sample was calculated by constructing a calibration curve in which the molecular weight log of glucan standards 180, 1000, 5000, 12000, 50000 and 64650 Da was plotted using the Agilent Chemical Station GPC Data Analysis software (Rev.A.02.01).