Expression and purification of recombinant Lactobacillus casei bacteriocin and analysis of its antibacterial activity

Diseases caused by foodborne pathogens have largely promoted the search for natural biopreservatives. We constructed recombinant plasmids pGEX-4 T-1-lacA, pGEX-4 T-1-lacB, and pGEX-4 T-1-lacAB, harboring genes for bacteriocins lactocin (Lac) A, B, and AB, respectively, with protein expression achieved in Escherichia coli BL21 cells. LacAB was purified using a glutathione S-transferase (GST) protein purification kit, and the GST tag was removed using thrombin for a maximum concentration yield of 1.85 mg/mL. LacAB and the combination of LacA and LacB showed better antimicrobial activity than LacA or LacB alone. The antibacterial activity assay indicated that purified LacAB has broad-spectrum and significant antimicrobial activity against Staphylococcus aureus ATCC25923, with a minimum inhibitory concentration of 125 mu g/mL. This study is the first, to our knowledge, to demonstrate the antimicrobial activity of LacAB; moreover, it provides an efficient strategy for the production of bacteriocin LacAB, which could be a food preservative candidate.