Structural analysis and properties of dextran produced by Leuconostoc mesenteroides NRRL B-640

A water-soluble dextran was produced by purified dextransucrase from Leuconostoc mesenteroides NRRL B-640. The dextran was purified by alcohol precipitation. The structure of dextran was determined by FT-IR, 1H NMR, 13C NMR and 2-dimensional NMR spectroscopic techniques. NMR techniques (1D 1H, 13C and 2D HMQC) were used to fully assign the 1H and 13C spectra. All the spectral data showed that the dextran contains d-glucose residues in a linear chain with consecutive α(1 → 6) linkages. No branching was observed in the dextran structure. The viscosity of dextran solution decreased with the increase in shear rate exhibiting a typical non-Newtonian pseudoplastic behavior. The surface morphology of dried and powdered dextran studied using Scanning electron microscopy revealed the cubical porous structure.