Optimization, purification, characterization and antioxidant activity of an extracellular polysaccharide produced by Paenibacillus polymyxa SQR-21

The optimization, purification and characterization of an extracellular polysaccharide (EPS) from a bacterium Paenibacillus polymyxa SQR-21 (SQR-21) were investigated. The results showed that SQR-21 produced one kind of EPS having molecular weight of 8.96 × 10⁵ Da. The EPS was comprised of mannose, galactose and glucose in a ratio of 1.23:1.14:1. The ratio of monosaccharides and glucuronic acid was 7.5:1. The preferable culture conditions for EPS production were pH 6.5, temperature 30 °C for 96 h with yeast extract and galactose as best N and C sources, respectively. The maximum EPS production (3.44 g L⁻¹) was achieved with galactose 48.5 g L⁻¹, Fe³⁺ 242 μM and Ca²⁺ 441 μM. In addition, the EPS showed good superoxide scavenging, flocculating and metal chelating activities while moderate inhibition of lipid peroxidation and reducing activities were determined. These results showed the great potential of EPS produced by SQR-21 to be used in industry in place of synthetic compounds.