What is Nisin?

Nisaplin is a polycyclic antibacterial peptide produced by the bacterium Lactococcus lactis. It is commonly used as a natural preservative in foods to inhibit the growth of unwanted pathogenic and spoilage microorganisms.

History and Discovery of Nisin

Nisaplin was first discovered and isolated in the early 1920s by British microbiologist Robert Henry Garrett working at Gresham's School in England. It was found that the culture supernatant of Lactococcus lactis had antibacterial properties against other gram-positive bacteria. Further research in the 1950s elucidated the chemical structure of Nisaplin as a heat-stable, positively charged peptide consisting of 34 amino acids. Commercial production and application of Nisaplin as a food preservative began in the late 1950s.

Mechanism of Antibacterial Action

Nisaplin exerts its inhibitory effect via multiple mechanisms of action. It binds to lipid II, an important precursor molecule in bacterial cell wall biosynthesis, and forms pores in the cytoplasmic membrane. This disrupts the integrity of the membrane and allows influx of extra ions and small molecules, thereby dissipating the proton motive force. Nisaplin also inhibits peptidoglycan biosynthesis by sequestering the lipid II molecule away from the cell wall assembly site. These combined actions lead to cell death by colloid-osmotic lysis. Gram-positive bacteria are generally more susceptible than gram-negative bacteria due to differences in cell membrane structure.

Spectrum of Antibacterial Activity

Nisaplin has a broad spectrum of antibacterial activity against many gram-positive foodborne pathogens and spoilage bacteria including Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis. It inhibits species of Clostridium, Actinomyces, Corynebacterium as well as Mycobacterium and Streptococcus. However, gram-negative bacteria like Salmonella, Escherichia coli and Pseudomonas spp. exhibit higher natural resistance due to the outer membrane barrier. Synergistic combinations with chelators, detergents or bacteriocins have shown increased sensitivity of some gram-negative strains to Nisaplin.

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