Background: Dextran is a bacterial polysaccharide composed of chains of D-glucose units. Most of the
commercial strains for dextran production belong to Leuconostoc Spp. Dextran has many uses in the
pharmaceutical, food and textile industries.
Objectives: The objective of this study was to elucidate the characteristics and structural aspect of the
dextran synthesized by purified novel dextransucrase of Acetobacter tropicalis.
Methods: The solubility of the dextran was checked in various solvents and viscosity was determined
by jacketed Ostwald Viscometer. Optical rotation and molecular weight were evaluated by using polarimeter
and gel permeation chromatography, respectively. Finally, the structural characteristics were
studied by FTIR, NMR and SEM techniques.
Results: From the results, it has been concluded that the water-soluble dextran was dextrorotatory. The
FTIR, 1H NMR, 13C observations confirmed the presence of D-glucose residues arranged in a linear
chain with consecutive α (1-6) linkages without any branching. The surface morphology of vacuum
dried, powdered dextran studied by using Scanning electron microscopy revealed its porous nature.
The molecular weight determined by gel exclusion chromatography was found to be in the range from
10-40 kDa (~ 25 kDa).
Conclusion: Unique dextran was synthesized by purified dextransucrase from newly isolated A.
tropicalis. It is unique because of its linear structure, highly porous nature and small molecular weight.
Native dextran with such combination has not been reported by dextransucrase of indigenous bacterial
strains. This kind of dextran has high value in food industries, clinical use and therapeutics.