Structural analysis and characterization of dextran produced by wild and mutant strains of Leuconostoc mesenteroides

An exopolysaccharide known as dextran was produced by Leuconostoc mesenteroides KIBGE-1B22 (wild) and L mesenteroides KIBGE-IB22M20 (mutant). The structure was characterized using FTIR, H-1 NMR, C-13 NMR and 2D NMR spectroscopic techniques, whereas surface morphology was analyzed using SEM. A clear difference in the spectral chemical shift patterns was observed in both samples. All the spectral data indicated that the exopolysaccharide produced by KIBGE-IB22 is a mixture of two biopolymers. One was dextran in alpha-(1 -> 6) configuration with a small proportion of a-(1 : 3) branching and the other was levan containing beta-(2 : 6) fructan fructofuranosyl linkages. However, remarkably the mutant only produced dextran without any concomitant production of levan. Study suggested that the property of KIBGE-IB22M20, regarding improved production of high molecular weight dextran in a shorter period of fermentation time without any contamination of other exopolysaccharide, could be employed to make the downstream process more feasible and cost effective on large scale. (C) 2013 Elsevier Ltd. All rights reserved.