Objective:To express Milk-derived angiotensin-I converting enzyme(ACE) inhibitory peptides in Lactococcus lactis(L.lactis).Methods:The four different Bovine casein-derived peptides were chosen and designed as tandem peptides(TP) with digestive enzyme restriction site among them to ensure the potent ACE inhibitory activity of TP could be activated by pepsin and trypsin in human digestive juice.The TP gene was synthesized artificially based on its amino acid sequence and bias codon of L.lactis.Then,the TP gene was co-expressed with green fluorescent protein(GFP),which was cloned in expression vector pSEC-E7 resulting in the pSEC-TP:GFP plasmid.This recombinant plasmid was transformed into L.lactis strain NZ9000 carrying regulatory genes nisR and nisK to obtain the strain NZ9000(pSEC-TP:GFP) by electroporation.The expression of TP:GFP gene induced by Nisin was identified by RT-PCR,SDS-PAGE and Confocal scanning laser micrographs.Results:RT-PCR showed that the TP:GFP was expressed at the RNA level.SDS-PAGE analysis showed target proteins product of 35 ku.Conclusion:The expression of Milk-derived ACE inhibitory peptide has been detected in Lactococcus lactis.