In vitro antioxidant activities of an exopolysaccharide from a salt pan bacterium Halolactibacillus miurensis

Exopolysaccharide (EPS) designated as HMEPS was isolated from Halolactibacillus miurensis and purified through gel filtration chromatography. EPS extracted from the supernatant yielded a 56.1% total carbohydrate content. The ash and moisture content were 12.1% and 1.5% respectively. Galactose and glucose were found as main monosaccharides of the HMEPS through HPLC analysis. FT-IR spectra of the HMEPS revealed its composition with hydroxyl, alkenes, amide and carboxyl as functional groups and aliphatic amine and alkynes at the fingerprint region. In vitro antioxidant activity was investigated against hydroxyl, DPPH, superoxide free radicals and the scavenging activity against all were found to be dose dependent proportionately. HMEPS showed higher reducing ability against superoxide radical and potency in chelating the ferrous ions. 10 mg/ml of HMEPS was found equivalent to 2.7 units of ascorbic acid through the total antioxidant assay. Phylogenetic relation of H. miurensis SEEN MKU3 (GenBank number KT803852) was plotted with MEGA 5.0.