|Jmol-3D images||Image 1|
|Molar mass||3354.07 g/mol|
|Boiling point||2,966 °C; 5,371 °F; 3,239 K|
| (what is: / ?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Nisin is a polycyclic antibacterial peptide with 34 amino acid residues used as a food preservative. It contains the uncommon amino acids lanthionine (Lan), methyllanthionine (MeLan), didehydroalanine (Dha) and didehydroaminobutyric acid (Dhb). These unusual amino acids are introduced by posttranslational modification of the precursor peptide. In these reactions a ribosomally synthesized 57-mer is converted to the final peptide. The unsaturated amino acids originate from serine and threonine, and the enzyme-catalysed addition of cysteine residues to the didehydro amino acids result in the multiple (5) thioether bridges.
Nisin is produced by fermentation using the bacterium Lactococcus lactis. In the food industry, it is obtained from the culturing of L. lactis on natural substrates, such as milk or dextrose, and is not chemically synthesized.
While in general most bacteriocins inhibit only closely related species, nisin is a rare example of a "broad-spectrum" bacteriocin effective against many Gram-positive organisms, including lactic acid bacteria (commonly associated with spoilage), Listeria monocytogenes (a known pathogen), Staphylococcus aureus, Bacillus cereus, Clostridium botulinum, etc. It is also particularly effective against spores. Gram-negative bacteria are protected by their outer membrane but may become susceptible to nisin action after a heat shock or when this is coupled with the chelator EDTA. Nisin is soluble in water and can be effective at levels nearing the parts-per-billion range.
Nisin is used in processed cheese, meats, beverages, etc. during production to extend shelf life by suppressing Gram-positive spoilage and pathogenic bacteria. In foods, it is common to use nisin at levels ranging from ~1-25ppm, depending on the food type and regulatory approval. As a food additive, nisin has an E number of E234.
Due to its naturally selective spectrum of activity, it is also employed as a selective agent in microbiological media for the isolation of gram-negative bacteria, yeast, and moulds. In combination with miconazole it has been studied as a possible treatment for infections of Clostridium difficile.
Ongoing research seems to indicate that nisin may also have potential for slowing the growth of certain tumors.
- K. Fukase et al., Tetrahedron Lett. 1988, 29, 7, 795. (Total synthesis)
- G. W. Buchman et al., J. Biol. Chem. 1988, 263, 31, 16260. (Biosynthesis)