Inhibition Effect Of Nisin And ε-pL Synergy And Application In Chicken Breas

Nisin and ε-polylysine which are two natural antibacterial peptides produced by the microbial metabolism, have good inhibitory effect. The meat products are easily spoiled because of the microbial action, so the shelf life of these products is short. Some chemical preservatives have become an important cause of consumer distress, so the use of natural, safe and efficient preservatives will be more concerned by the food industry.In this study, the antibacterial effects of the combination of nisin and ε-PL against different spoilage bacteria including Enterococcus faecalis R6-12-Z1、Enterococcus faecium R-615-Z1、Enterococcus durans KLD6.0603、Enterobacter cloaca C4、Enterobacter cloaca C1、Enterobacter coli DH5α were firstly determined based on the minimum inhibitory concentration(MIC) and fractional inhibitory concentration(FICI), respectively. The cell membrane integrity of the treated bacteria was detected by fluorescence microscopy and SEM. The changes of intracellular membrane potential and reactive oxygen species were detected by fluorescence spectrophotometer.Finally, the antibacterial effects of the combination of nisin and ε-PL to the main spoilage bacteria were further studied in chicken meat products. The total bacteria count, volatile basic nitrogen(TVB-N), p H and biogenic amines at different storage days were analyzed.The results showed that the combination of nisin and ε-PL showed synergistic antibacterial activity against the above strains. The cell membranes of the bacteria treated by the combination of nisin and ε-pL were damaged more heavily than those treated single by nisin or ε-pL shown by fluorescence microscopy and SEM. The combination of nisin and ε-pL can produce a high reactive oxygen species level in the treated bacterial cells, and the changes of membrane potential was also the same result. Nisin and ε-pL inhibitory mechanism, the main reason may be nisin first target bacteria cells to produce holes, then ε-pL quickly enter the cell, and other structures within the cell interaction, including increasing the level of ROS, the impact of potential energy, and thus inhibit the growth of target bacteria.Finally, the chicken meat products which were inoculated Enterococcus faecalis R-612-Z1 and Enterobacter cloaca C4 separately were subjected to the following antimicrobial treatment: N1(no nisin/ε-PL added; control sample), N2(ε-PL 0.25 g/kg, no nisin added), N3(ε-PL 0.125 g/kg, no nisin added), N4(nisin 0.5 g/kg, no ε-PL added), N5(nisin 0.25 g/kg, no ε-PL added), N6(nisin0.25 g/kg, ε-PL 0.125 g/kg), N7(nisin 0.125 g/kg, ε-PL 0.125 g/kg), and N8(nisin 0.125 g/kg,ε-PL 0.06 g/kg). The bacterial counts, and the contents of TVB, biogenic amines of N6 andN7 groups were significantly lower than those of the other groups.The results of this study showed that the combination nisin and ε-pL had synergistic antibacterial activity against the selected Gram-positive and Gram-negative bacteria through producing a high reactive oxygen species level and damaging the cell membrane structure. It was found that the combination of nisin and ε-PL was more effective than application of nisin or ε-PL alone with twofold concentration to control microorganisms and production of biogenic amines in chicken meat products.