The molar mass was determined using

The molar mass was determined using size exclusion chromatography (SEC),as described in literature.Samples were activated sufficiently in DI water, and then were subjected to the solvent exchange three times with both methanol and Dimethylacetamide DMAc). Each sample was added into 8 % LiCl/DMAc. The mixture was stirred gently and left at 4°C for 5 days. The formed solutions were diluted to the concentration of 0.5 % (wt %).Ultimately, prior to chromatographic characterization, the solutions of cellulose samples were filtered through a 0.45-µm poly (tetrafluorethylene) filter and stored in vials. The SEC system was consisted of a DGU-20A3 degasser (Shimadzu),a LC-20AD liquid chromatography (Shimadzu), a Rheodyne 7725i fixed loop (100 µl) and a RID-10A refractive index detector(Shimadzu). The separation system consisted 23 of a mixed-A 20 µm guard column (7.5 × 50mm,Polymer Laboratories) and four mixed-A20µm columns (7.5 × 300 mm,Polymer Laboratories) connected in series. The flow rate was set at 0.5 ml/min.The columns were thermostated at 80°C and the mobile phase was 0.5%LiCl/DMAc. The linear coefficient of determination (r2) was 0.996 for the curve of pullulan molecular weight versus the elution time.The system and data were controlled and evaluated with LC Solution software (Shimadzu).