E-numbers / Preservatives / E234
also: Nisin A · Lactococcal bacteriocin
A natural antimicrobial peptide produced by bacteria during fermentation, used to prevent bacterial spoilage in cheese, cream and some meat products.
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Nisin is a bacteriocin, a small protein-like molecule produced by the bacterium Lactococcus lactis during fermentation.
4
of the 43,325 UK supermarket foods we checked declare E234 in their ingredients
That is under 0.1%, counted by its code or its name.
Counted by NutraSafe from UK supermarket ingredient lists, September 2026. How we counted
Nisin is a bacteriocin, a small protein-like molecule produced by the bacterium Lactococcus lactis during fermentation. It belongs to a class called lantibiotics, containing unusual ring structures formed from modified amino acids. Commercially it is sold as nisin preparation, a powder that is roughly 2.5% pure nisin by weight, with the remainder being dried food-grade carrier material from the fermentation broth.
Nisin targets a molecule called Lipid II, which Gram-positive bacteria need to build their cell walls. By binding to Lipid II and punching holes in bacterial membranes, nisin prevents bacteria from growing or forming heat-resistant spores. It is effective against a specific range of Gram-positive bacteria, including Listeria monocytogenes, Staphylococcus aureus and Clostridium botulinum. It has no activity against Gram-negative bacteria, yeasts or moulds. Once ingested, nisin is broken down by digestive enzymes in the gut into its constituent amino acids, like any other small protein.
In the UK and EU, nisin is permitted in clotted cream, mascarpone, ripened and processed cheese and cheese products, unripened cheese, pasteurised liquid eggs, semolina and tapioca puddings, and heat-treated meat products. On a UK label it appears as E234 or as nisin preparation.
A 2023 study in pigs found that nisin consumed at realistic dietary levels reached the lower intestine intact and reduced populations of Gram-positive bacteria, particularly Lactobacillus species, while Gram-negative bacteria including E. coli increased. Short-chain fatty acid production, which beneficial gut bacteria generate from fibre, also fell during treatment. Crucially, all changes reversed within ten days of stopping nisin, and overall bacterial diversity remained stable. No equivalent controlled study has yet been carried out in humans.
Pig model study found nisin reversibly reduced Gram-positive gut bacteria including Lactobacillus and Bifidobacterium, with corresponding decreases in acetate (40%) and butyrate (66%) production; changes resolved within ten days of treatment ending.
Nisin acts on a bacterial target, Lipid II, that differs from the targets of conventional clinical antibiotics. Stable resistance to nisin is rarely observed in practice and, despite decades of food use, no widespread emergence of nisin-resistant strains has been reported. However, the 2017 EFSA panel explicitly declined to evaluate whether dietary nisin exposure could select for antimicrobial resistance or cross-resistance with other agents, and called for that question to be assessed separately. That assessment had not been published at the time of writing.
EFSA's 2017 safety panel noted that potential induction of antimicrobial resistance by dietary nisin and its modulating effect on gut microbiota were deliberately not evaluated and recommended a separate assessment of these risks.
Despite decades of food industry use, nisin resistance in clinically relevant bacteria has not emerged at a population level, partly because nisin targets Lipid II rather than protein synthesis pathways targeted by conventional antibiotics.
The key toxicology study was a 90-day rat feeding trial. The highest dose tested, 225mg nisin per kg of body weight per day, produced no adverse effects, establishing that as the no-observed-adverse-effect level. EFSA applied a 200-fold safety factor to account for species differences and the subchronic duration of the study, arriving at an ADI of 1mg/kg body weight per day. Estimated dietary exposure from all permitted uses falls well below that figure across all population groups. No genotoxicity was identified in the available data.
90-day rat feeding study identified a NOAEL of 225mg nisin/kg body weight per day, the highest dose tested; no adverse effects or genotoxicity were found.
EFSA revised the ADI upward from 0.13mg to 1mg nisin/kg body weight per day following the new subchronic toxicity data; estimated dietary exposure from all permitted uses was below the new ADI for all population groups.
No specific groups are required by food law to avoid nisin, and it is not a declarable allergen under UK food labelling rules. However, commercial nisin preparation is produced in fermentation media that may include dairy-derived components, so people with severe milk allergy should check with manufacturers. Look for E234 or nisin preparation on the label.
Nisin is one of the most thoroughly studied food preservatives, with a use history stretching back to the 1950s and two EFSA evaluations. The toxicology data at food-relevant doses are unremarkable. The two genuinely open questions are narrower than headline coverage sometimes implies: the gut microbiome shift seen in pig studies was reversible and did not affect microbial diversity; and while the EFSA 2017 panel deliberately left antimicrobial resistance uninvestigated, stable resistance to nisin has not emerged in practice despite decades of widespread food use. Both questions remain under-researched in humans, which is the honest limit of what the science currently shows.
No. Nisin is an approved food additive in the UK under the assimilated EU Regulation 1333/2008, listed on the FSA's approved-additives register. It is permitted in specific food categories including cheese, clotted cream and certain meat products.
A 2023 pig study found that nisin, consumed at levels consistent with normal dietary intake, temporarily reduced certain Gram-positive gut bacteria and lowered production of short-chain fatty acids. These changes reversed fully within ten days of stopping nisin. No equivalent controlled study has been done in humans, and the EFSA 2017 review did not formally assess gut microbiota effects.
In the UK, nisin is used mainly in ripened and processed cheeses, clotted cream, mascarpone, unripened cheese, heat-treated meat products, pasteurised liquid eggs, and semolina or tapioca puddings. On labels it appears as E234 or nisin preparation.
Nisin itself is produced by bacteria rather than directly from animals, but commercial nisin preparation is typically produced in dairy-based fermentation media and the powder may contain dried milk solids. Vegans and people with milk allergy should contact the manufacturer of a specific product for confirmation.
Last reviewed: 20 June 2026
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