Abstract: Objective: Cloning manganese superoxide dismutase gene (sodA) to make it express in Lactobacillus bulgaricus (L6032) to enhance its tolerance to oxygen was studied. Moreover, a foundation for developing SOD fermented milk was established. Methods: Using PCR to amplify sodA and cloning it into the Lactic acid bacteria expression vector pMG36e and then transforming this recombinant plasmid pMG36e-sod into L6032 by electroporation were studied; SOD reagent was used to detect its activity and to compare the growing situation and living condition as aerobes in MRS culture medium between L6032 and L6032-SOD. A preliminary inquiry into the effect of anti-oxygen of L6032 with SOD expression was made. Results: Construct- ing the recombinant plasmid pMG36e-sod successfully has been identified with the prospect by means of enzyme digestion and PCR. The result of sequencing showed that the insert gene could encode SOD correctly; After successfully transforming pMG36e-sod into L6032 by electroporation the activity of SOD was about 590.5NU∕mg prot. Furthermore, enhancing L. bulgaricus’s tolerance to oxygen has not only made L6032-SOD grow better than L6032 under the same condition, but also improved the living rate of bacteria obviously. Conclusion: sodA has been successfully for expressed in L. bulgaricus to have enhanced its tolerance to oxygen. It was beneficial to develop and apply Lactobacillus. At the same time, this study has laid a foundation for further developing SOD fermented milk.

Key words: lactobacillus, superoxid dismutase, gene cloning and expression