Nisin

Nisin is a natural antimicrobial peptide produced during fermentation by the lactic acid bacterium Lactococcus lactis. It was discovered in dairy fermentation in the 1920s and has been used as a food preservative since the 1950s, making it one of the oldest commercially used biopreservatives. It is active against Gram-positive bacteria including Listeria monocytogenes, Clostridium botulinum, Staphylococcus aureus, and Bacillus spores — pathogens of major food safety concern. Common applications include processed cheese, canned tomatoes, pasteurised cream, and dairy desserts.

JECFA's ADI for nisin is "not specified," evaluated in 1969. Nisin is a peptide and is rapidly broken down by digestive proteases in the stomach and small intestine, producing only amino acids and small peptides — compounds already present in all protein-containing foods. There is no systemic absorption of intact nisin at food additive levels, and no adverse effects have been identified in human or animal safety studies.

Nisin is approved in the EU, US (GRAS), Australia, and many global markets. Unlike synthetic chemical preservatives, nisin's natural origin and complete digestive degradation give it a strong safety profile and increasing appeal in "clean label" food formulations. It does not contribute to antibiotic resistance — despite being classified as an antibiotic in clinical medicine, its mechanism of action (cell wall disruption) and complete digestive breakdown mean it has no impact on gut antibiotic resistance patterns. For consumers, E234 is among the most benign preservatives on the market.