Structural Characterization of Insoluble Dextran Produced by Leuconostoc mesenteroides NRRL B-1149 in the Presence of Maltose

Abstract

Leuconostoc mesenteroides NRRL B-1149 is known to produce dextran with 52 % α-(1→6) and 40 % α-(1→3) linkages. Low solubility of dextran in water is associated with the presence of high percentage of α-(1→3) linkages. Leuconostoc mesenteroides NRRL B-1149 produces two types of enzymes, dextransucrase and fructansucrase, which are active with sucrose and raffinose, respectively, as confirmed by the activity staining. The insoluble dextran was synthesized using partially purified dextransucrase in the presence of maltose. A water-soluble dextran was also produced by dextransucrase from Leuconostoc mesenteroides NRRL B-1149. The produced insoluble dextran was purified by alcohol precipitation, and then structurally characterized using FTIR, 1H NMR, and 13C NMR spectroscopic techniques. From the spectral analysis, it was confirmed that the insoluble dextran produced by Leuconostoc mesenteroides NRRL B-1149 contained dextran with α-(1→6) linkages and α-(1→3) branched linkages. The surface morphology of dried and powdered dextran studied using scanning electron microscopy revealed its fibrous structure.

Keywords

• dextransucrase
• Leuconostoc mesenteroides NRRL B-1149
• dextran
• insoluble dextran
• FTIR
• NMR