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

Rishikesh Shukla1, Shraddha Shukla1, Veselin Bivolarski2, Ilia Iliev2, Iskra Ivanova3 and Arun Goyal1*

1Department of Biotechnology, Indian Institute of Technology Guwahati, 781 039 Guwahati,
Assam, India
2Department of Biochemistry and Microbiology, Plovdiv University, 24 Tzar Assen Str, BG-4000 Plovdiv, Bulgaria
3Department of General and Applied Microbiology, Biological Faculty, Sofia University, 8 Dragan Tzankov Str, BG-1164 Sofia, Bulgaria

Article history:

Received September 13, 2010
Accepted January 28, 2011

Key words:
dextransucrase, Leuconostoc mesenteroides NRRL B-1149, dextran, insoluble dextran, FTIR, NMR, SEM


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.

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