Abstract:

In this study, a marine strain named OST23a with the ability to produce antioxidant exopolysaccharide (EPS) was screened out of the strains isolated from the samples of sea water or sea mud collected from the sea area near Lianyungang. The strain OST23a was identified as Bacillus subtilis according to its morphological, physiological, biochemical characteristics and 16S rRNA sequence. The EPS produced by this strain exhibited an obvious antioxidant activity. The optimal carbon and nitrogen sources as well as metal ion for the production of EPS were determined to be n-hexane, yeast extract and CaCl2 by single-factor experiments. The optimal formula of fermentation medium for the production of EPS by OST23a were explored to be 1.5% n-hexane, 0.1% yeast extract, 0.3% K2HPO4, 0.1% KH2PO4, and 0.1% CaCl2 by orthogonal array experiments. The productivity of EPS was up to 9.06 mg/L using this optimal medium.

Key words: marine strain, EPS, antioxidant activity, screening, medium composition