Effect of ecological factors on the inhibitory spectrum and activity of bacteriocins

The effect of food components and ecological factors on the activities of nisin, sakacin P and curvacin A was evaluated. Lactobacillus curvatus, Listeria innocua, Salmonella and Escherichia coli including E. coli O157:H7 were used as target organisms. Lecithin, casein, and divalent cations were antagonists of the bacteriocins at 0.1%, 0.1% and 10 mmol l−1, respectively. A decrease in pH as well as the presence of EDTA, propyl-parabene or NaCl at concentrations of 0–1 mmol y−1, 0–0.16 g l−1, and 0–6% (w/w), respectively, increased the activity of all bacteriocins. These compounds as well as a pH<5.5 rendered the Gram-negative target organisms sensitive against bacteriocins. Of practical importance is the respective effect of NaCl at concentrations >5% which are achieved in fermentation and ripening processes, e.g. in production of fermented sausages. A characteristic response was observed for each of the bacteriocins. It is suggested that bacteriocins of lactic acid bacteria are effective against a wide range of microorganisms including E. coli O157:H7 if applied in combination with other preservative principles prevailing in foods.