Action Of Nisin Research Articles

The effect of nisin‐sodium chloride interactions on the outgrowth of Bacillus licheniformis spores

The effect of salt (NaCl) on the efficacy of nisin in preventing outgrowth of Bacillus licheniformis spores was determined in Plate Count Agar (PCA). An equivalent liquid medium was used for heat activation. Nisin and salt were added to the heat‐activation medium, the PCA, or both. The spores were extremely sensitive to nisin; outgrowth were completely inhibited in salt‐free media when 10 iu/ml of nisin was present in both the heat‐activation and the growth media or when 100 iu/ml nisin was present in either the heat‐activation and the growth medium. In media supplemented with 1% salt, outgrowth occurred from 1% of spores exposed to 100 iu/ml nisin in either the heat‐activation or the growth medium. A 3% salt supplement was necessary before detectable outgrowth occurred when both the heat‐activation and the growth media contained 100 iu/ml nisin. Salt appears to antagonize the sporicidal action of nisin by interfering with nisin adsorption onto the spore.

Mode of action of the peptide antibiotic nisin and influence on the membrane potential of whole cells and on cytoplasmic and artificial membrane vesicles.

The peptide antibiotic nisin was shown to cause a rapid efflux of amino acids and Rb+ from the cytoplasm of gram-positive bacteria (Staphylococcus cohnii 22, Bacillus subtilis W 23, Micrococcus luteus ATCC 4698, and Streptococcus zymogenes 24). It strongly decreased the membrane potential of cells as judged by the distribution of the lipophilic tetraphenylphosphonium cation. Ascorbate-phenazine methosulfate-driven transport of L-proline by cytoplasmic membrane vesicles was blocked after addition of nisin, and accumulated amino acids were released from the vesicles. Soybean phospholipid (asolectin) vesicles were not affected by nisin. The data suggest that the cytoplasmic membrane is the primary target and that membrane disruption accounts for the bactericidal action of nisin.

Effect of Nisin on the Outgrowth of Clostridium botulinum Spores

ABSTRACTNisin, an antibiotic produced by certain strains of Streptococcus lactis, is effective in preventing the outgrowth of Clostridium botulinum spores. Type A C. botulinum spores were the most resistant to the inhibitory action of nisin requiring 1000‐2000 I.U. of nisin/ml for a 50% inhibition of outgrowth on TPYG agar plates. Type E spores were more sensitive requiring only 50‐100 I.U./ml for 50% inhibition of outgrowth on TPYG agar plates. Type B spores displayed an intermediate level of sensitivity requiring 500‐1000 I.U. of nisin/ml for 50% inhibition of outgrowth on TPYG agar plates. Similar levels of nisin were necessary to prevent spore outgrowth in TPYG broth and BHI broth over a 7‐day incubation period. With prolonged incubation periods of up to 65 days in TPYG broth, spore outgrowth was observed sporadically at higher nisin levels with the type A and B spores which may indicate some decomposition of nisin with storage. Nisin levels of 5000 I.U./ml for the type A spores and 2000 I.U./ml for the type B spores and the Minnesota E spores were insufficient to prevent spore outgrowth by C. botulinurn in cooked meat medium. For the Beluga E spores, a nisin level of 2000 I.U./ml was necessary to prevent spore outgrowth in cooked meat medium. The need for higher levels of nisin in cooked medium to prevent spore outgrowth may be due to the binding of the nisin by meat particles.

Effect of Nisin on Heat Resistance and Gas Production of some Spore-Formers

Summary Thermal treatment of spores of B. subtilis in the presence of the antibiotic nisin in phosphate buffer at pH. 6.4 (using high dilution factor, i.e., high density of spores) showed that nisin lowers the heat resistance of spores. The use of high dilution factor disputes the conception of some investigators that the lowering in the spore count is apparently due to the carry-over of nisin in the recovery medium. The effect of nisin on the rate of gas production by Cl. welchii spores, measured in Smith fermentation tubes, was investigated. It was found that nisin in high concentration (1,000 R.U./ml) completely inhibited growth and gas production. Nisin in low concentrations, namely: 100 and 200 R.U./ml, retarted the rate of gas production, being higher in 200 R.U./ml than in 100 R.U./ml. In these two concentrations the amounts of gas were generally lower than in the control. This was attributed to the direct action of nisin on enzymes involved in gas production.

Mode of Action of Nisin on some Representative Bacterial Spores

Summary The mode of action of nisin on the most dominant aerobic and anaerobic spore-formers, isolated from milk and processed cheese, together with some known strains was studied. The effect of nisin on 12 times washed spores of aerobic spore-formers, representing the three groups put forward by Smith, Gordon, and Clark (1952). From group I, two strains of B. subtilis, B. megatherium, B. licheniformis , and B. coagulans . From group II B. stearathermophilus and B. polymyxa . From group III B. sphaericus . Anaerobic spore-formers, namely Cl. welchii and Cl. sporogenes , were studied in phosphate buffer M/100 at p H 6.4. It was generally found that nisin exerted neither sporocidal effect nor any germination induction on spores of the afore-mentioned species. This, in fact, came to after several trials in which high dilution factor was used to eliminate the carry over of nisin in the recovery media. When low dilution factor was used, anomalous results were obtained. The use of high dilution factor dispute the conception that nisin is firmly bound to the spores, but it can be stated that it only remained in the surrounding medium, hence lost through dilutions, thus count restored to normal. The concept of carry-over of nisin to the recovery media when the low dilution factor was used, giving anomalous results and thus inducing several investigators to state a sprocidal effect, was fully confirmed. This was established by the inactivation of nisin in the origin or in the recovery media by proteolytic enzymes (trypsin and pancreatin) or by adjusting the p H to alkalinity (phosphate buffer at p H 8). Both treatments restored the count to normal, i.e., being in the same order as the initial, indicating that nisin has sporostatic but no sporocidal effect.

Effect of butterfat on inhibition of Staphylococcus aureus by nisin.

Nisin in brain heart infusion medium (Difco) and Bacto-Staphylococcus medium 110 completely inhibited the growth of Staphylococcus aureus 196. This restraining action of nisin on S. aureus was not as effective in the presence of whole milk. This was especially noted when attempts were made to control growth of S. aureus in cheese made with starter inactivated by phage. Although nisin had some inhibitory action on S. aureus in cheese it was not equal to that exerted by an active Streptococcus lactis culture. Its presence failed to prevent production of enterotoxin A. A factor influencing the failure of nisin to control growth of S. aureus in cheese was the presence of butterfat which was shown to interfere with the action of nisin against the growth of S. aureus.

The biological effects of food additives. I.—Nisin

AbstractNisin has been administered to rats at three dosage levels in cheese, in which it had been prepared in situ, and at two dosage levels as the commercial product (Meganisin) added to a basal diet.The effects of nisin have been assessed by examining the rate of body‐weight gain, the food intake, the reproductive performance, survival of young, the haematological picture, organ weights, mortality rate and gross and microscopical appearance of the organs. In addition, gastrointestinal, renal and hepatic functions have been studied.Special attention has been paid to possible antimetabolic and nephrotoxic actions of nisin. The sensitising action of nisin has been investigated in the guinea‐pig.Although nisin appeared to depress growth rate of male rats in one test at only 14 times the possible human dosage level, normal growth was found in other tests at 1400 times this dosage level. Depression of growth rate was associated with reduced food intake. There was no other consistently significant finding and it has been concluded that nisin is a safe substance for use in food at the level of treatment proposed.