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.