Purification, characterization and functional properties of exopolysaccharide from a novel halophilic Natronotalea sambharensis sp. nov.

An exopolysaccharide producing strain AK103 was isolated from Sambharlake, Rajasthan, India. Based on polyphasic taxonomy, the strain AK103 was found to be a novel species for which the name Natronotalea sambharensis sp. nov. is proposed. The strain was able to secrete (1.2 gL) EPS under optimum conditions. The FT-IR spectroscopy revealed that EPS had carboxyl, hydroxyl, carbonyl and sulfate ester groups. The high performance liquid chromatography (HPLC), gel permeation chromatography (GPC) and NMR revealed that the exopolysaccharide was composed of mannose, glucose and glucuronic acid with a molecular weight of 4.6 × 10 KDa. This novel EPS was designated as Nat-103. Interestingly, the EPS was found to have antioxidant activity and in vitro antioxidant studies showed that DPPH (2,2-diphenyl-1-picrylhydrazyl) activity increased in a dose dependent manner. Furthermore, EPS Nat-103 was able to produce gold nanoparticles which were further characterized by FT-IR, DLS and Zeta potential (ZP).