Resistance of Lactobacillus casei KCTC 3260 to reactive oxygen species (ROS): role for a metal ion chelating effect

The antioxidative capacity of 4 Lactobacillus strains, isolated from a milk product, was evaluated by measuring total antioxidative ability (TAA) and resistance to reactive oxygen species (ROS). Both intact cells and intracellular cell-free extracts of Lactobacillus casei KCTC 3260 demonstrated the highest antioxidative activity and inhibited lipid peroxidation by 46.2% and 72.9%, respectively. To evaluate the resistance of 4 Lactobacillus strains to ROS, we tested the survival under conditions of 1 mM hydrogen peroxide, 0.4 mM hydroxyl radicals, and 10 mM paraquat-induced superoxide anions. L. casei KCTC 3260 was viable even after 8 h in the presence of 1 mM hydrogen peroxide and after 7 h in 0.4 mM hydroxyl radicals. Moreover, this strain was not influenced by superoxide anions, indicating that it has resistance to superoxide anions. To define the antioxidative mechanism, superoxide dismutase (SOD) and metal ion chelating activity were determined. All tested strains did not possess detectable SOD activity except Lactobacillus rhamnosus GG, but L. casei KCTC 3260 had the higher level of chelating activity for both Fe(2+) and Cu(2+) ions at 10.6 ppm and 21.8 ppm, respectively. These results suggested that the antioxidative capacity of L. casei KCTC 3260 may be caused by chelating metal ions instead of SOD activation.