RÉSUMÉ
Because of widespread interests to biopreservatives, several studies have been conducted within last decades that show the nisin has been used as a preservative to control food borne spoilage microorganisms. The aim of this study was to evaluate anti-bacterial activity of nisin and its effect on decreasing concentration of current chemical preservatives. In this experimental study, anti-bacterial activity of nisisn and its effect on decreasing concentration of usual chemical preservatives against Staphylococcus aureus [PTCC 1112] and Listeria monocytogenes [PTCC 1301] were studied. The study was performed in two steps. First, MIC [minimum inhibitory concentration] and MBC [minimal bactericidal concentration] of preservatives, including sodium nitrite, benzoic acid and nisin, were measured in optimum ph [5.5] by serial dilution method. Second, MIC of sodium nitrite and benzoic acid were determined in combination with nisin. Sodium nitrite, benzoic acid and nisin had antibacterial activities against Staphylococcus aureus and Listeria monocytogenes; MIC was 500, 200 and 25 ppm for Staphylococcus aureus, and 100, 200 and 10 ppm for Listeria monocytogenes, respectively. Niacin reduced MIC of sodium nitrite and benzoic acid to 200 and 50 ppm for Staphylococcus aureus, and 25 and 25 ppm for Listeria monocytogenes, respectively. The nisin reduces chemical preservatives concentration required, and it could be used as a safe preservative in food microbiology