Effect of treatment conditions on nisin inactivation of gram-negative bacteria

A method using nisin and a chelating agent to inactivate Salmonella species and other gram-negative bacteria has been developed. The objective of this study was to determine the effect of treatment conditions on the application of this method. Ten gram-negative organisms were used in this study, including six Salmonella species commonly associated with foodborne illness. Organisms were selected on the basis of sensitivity to nisin and a chelating agent. The following parameters were examined: (a) chelating agent, (b) nisin concentration, (c) incubation temperature, and (d) protein interference. Chelating agents included EDTA, ethylenebis (oxyethylene-nitrilo) tetraacetic acid, citric acid monohydrate, and sodium phosphate dibasic. The most effective treatment consisted of 50 to 100 micrograms/ml nisin applied in combination with 20 mM EDTA or citric acid monohydrate at a temperature range of 30 to 42 degrees C. All of the chelators examined exhibited some inhibitory activity. The addition of bovine serum albumin to the treatments containing nisin and EDTA did not result in a significant decrease in inhibitory action