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, H-1 NMR, C-13 NMR and 2-dimensional NMR spectroscopic techniques. NMR techniques (1D H-1, C-13 and 2D HMQC) were used to fully assign the H-1 and C-13 spectra. All the spectral data showed that the dextran contains D-glucose residues in a linear chain with consecutive alpha(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 dextrain studied using Scanning electron microscopy revealed the cubical porous structure. (C) 2008 Elsevier Ltd. All rights reserved.