Synergetic activity of nisin with cell-free supernatant of Bacillus licheniformis ZJU12 against food-borne bacteria

Antibacterial activity of nisin and cell-free supernatant of Bacillus licheniformis ZJU12 (CFSb), separately and in combination, against three food-borne bacteria: Micrococcus flavus, Bacillius cereus and Staphylococcus aureus was determined. M. flavus was more sensitive to nisin and CFSb than other two indicator strains in the MIC tests. Synergetic activity of nisin and CFSb was found against all the three indicator strains in the checkerboard microtiter test and the time-kill test. The combination had the most notable antibacterial activity against B. cereus as determined by the fractional inhibitory concentration index (FICI). The antibacterial activity of nisin and CFSb separately began within the first 30 min, while their synergetic activity was observed after 4 h.