s Characterization and Structural Analysis of Unique Dextran Synthesized by Purified Dextransucrase of Newly Isolated Acetobacter tropicalis

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.