In order to clone active catalase gene from bacteria,we introduced a method of shotgun integrating specific sceen from Escherichia coli DH 5α.Genome DNA was extracted from E.coli DH5 and partially digested with Sau3AI.Then some fragments more than2.26kb were collected and ligated with T4 DNA ligase into the BamHI-cleaved plasmid pUC18 and transformed competent E.coli TG1 cells.The transforments were incubated ananaer obically on brain heart infusion (BHI)containing tannic acid.The method could detect catalase activity and screened the catalase-positive clones.And the catalase protein can be identified by SDS-PAGE.The results showed that the recombinant plasmid pUC18-kat was constructed successfully by PCR identifikation and restriction enzyme digestion.Open reading fram from DNA Sequence DH5a katE.The sequence long is 2262nt and coding protein are 753 Amino Acids,Molecular Weight 84198.72 Daltons.This method is simple,and possessed of popularization and application value.It would lay a fundation for cloning an active catalase later.Furtherly,In this study,the fragment of 2,262 bp catalase gene katE was cloned into the expression vector pQE30 and transformed into Escherichia coli M15,and KatE protein was expressed after the induction with Isopropylthio-β-D-galactoside.The KatE protein was separated on SDS-PAGE and recovered using a His-tag affinity.New Zealand white rabbits were immunized with the purified protein to harvest polyclonal antibodies.As L.lactis has no catalase,katE was inserted into Escherichia coli-L.lactis shuttle vector pMG36e and electrotransformed into L.lactis NZ9000.The expression of the KatE protein was confirmed by SDS-PAGE analysis and Western blot.Further experiment demonstrated that the expression of the KatE gene in L.lactis NZ9000 is able to produce active catalase that can provide efficient antioxidant activity.Additionally,to understand the import of catalase katE gene of Lactococcus lactis on the body physiological changes of immune function in mice.Enzyme-linked immunoassay (ELISA) was the blood of mice,IgG,IgE,and CD4 and CD8 levels,find out whether the difference between Grouping more mice eating the recombinant L.lactis NZ9000 and other groups (recombinant E.coli DH5α and L.lactis NZ9000,E.coli DH5α and saline) The experiments showed that recombinant L.lactis NZ9000 was significantly higher than the other on IgG concentrations,the difference was significant;IgE of CD4 of CD8 levels are no significant difference.Mice after the intake of recombinant L.lactis NZ9000 increased IgG levels explain recombinant L.lactis NZ9000 regulatory role of humoral immunity in mice;IgE level did not change CD4,CD8 levels were also no change,suggesting that there is no significant effect on the body of cellular immunity in a short time.