Effect of Treatment Conditions on Nisin Inactivation of Gram-negative Bacteria

Abstract

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 μg/ml nisin applied in combination with 20 mM EDTA or citric acid monohydrate at a temperature range of 30 to 42°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.

Synergistic Antimicrobial Effect of Nisin and ρ-Cymene onSalmonella entericaSerovar Typhiin Vitroand on Ready-to-Eat Food

“…8) Nisin is active against a wide range of gram-positive bacteria, although it is not effective against gramnegative bacteria. 9) However, when used in combination with agents destabilizing the outer membrane, it can inhibit gram-negative bacteria. -Cymene (4-isopropyltoluene or 1-isopropyl-4-methylbenzene) is a biological compound naturally present in the essential oils of oregano and thyme.…”

Anti-staphylococcal effectiveness of nisaplin in refrigerated pizza doughs

“…Other authors have noted the role of bacteriocins from Lactobacillus plantarum BN in improving the shelf-life of the refrigerated bovine meat (Fiorentini et al, 2001) and effectiveness of the concomitant application nisin/EDTA in inhibiting the growth of Gram-negative bacteria (Salmonella tiphymurium. S. infantis, S. heidelberg, S. choleraesuis, E. coli O157:H7) (Stevens et al, 1992;Cutter and Siragusa, 1995). Shefet et al (1995) found inhibitory effect of nisin when applied in combination of ETDA and citric acid on S. typhimurium in chicken meat.…”

“…The refrigerated pizza doughs are recognized as excellent substrates for the microbial growth being necessary to apply some procedures in order to control the growth and microbial survival in/on them (Cabo et al, 2001). Several authors have reported high microbial contamination in the food doughs (Stevens et al, 1992;Freitas et al, 2004). Staphylococcus has been known as pathogen microorganisms able to survive in the refrigerated pizza doughs (Freitas et al, 2004).…”

Action of nisin and high pH on growth of Staphylococcus aureus and Salmonella sp. in pure culture and in the meat of land crab (Ucides cordatus)

“…The nisin stock solution was prepared by dissolving 0.1 g of nisin in 10 mL of 0.02 N HCl (17). This solution was used to prepare the required nisin concentrations.…”

“…but does not inhibit the majority of Gram-negative bacteria (1,6,11). Nisin showed to be efficient in inactivating Gram-negative bacteria when used together with chelating agents (EDTA), causing an aberration in cell membrane lipopolisaccharyde component (17).…”