Study on antioxidant enzymes and exopolysaccharides of lactic acid bacteria separated from salt-dried fish products

In order to study the main active material with anti-oxidative effects of lactic acid bacteria (LAB) from salt-dried fish, the intracellular antioxidant enzymes and extracellular exopolysaccharides (EPS) were investigated. Vitality of superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) of nine strains were determined and the highest activity were 44.67, 15.26, and 1.23 U/mg prot respectively, which was corresponding to L21, L4 and L21. The crude EPS of LAB was prepared, and the production of nine LABs were between (5.71±0.18)–(50.33±1.89) mg/L, the highest purity of (56.16%±1.08%) was showed in a Lactobacillus casei (L21). The antioxidant capacity of EPS was then investigated by 1,1-diphenyl-2-picryhydrazyl (DPPH) radical scavenging and reducing power. The compositive antioxidant capacity was the highest in L21. Finally the structure of its EPS was analysed using ultra performance liquid chromatography (UPLC). The EPS of L21 contained four kinds of monosaccharides, namely, mannose (Man), rhamnose (Rha), glucose (Glu) and galactose (Gal). Thus, the nine LABs with high antioxidative capacity isolated from salt-dried fish showed higher antioxidant enzyme activity, and the production and purity of EPS were also high, and could show a certain antioxidant capacity in EPS. Therefore, the strongest comprehensive antioxidant strain was L21, and it could be further used as a biological antioxidant.