Lactococcuslactis Bacteria Produce Nisin, A Polycyclic Antibacterial Peptide Used In Processed Foods As A Natural Preservative

Nisin

The bacterium Lactococcus lactis produces the polycyclic antimicrobial peptide known as Nisin, which is used to preserve food. It contains 34 residues of different amino acids, including the rare ones lanthionine (Lan), methyllanthionine (MeLan), didehydroalanine (Dha), and didehydroaminobutyric acid (Dhb).

The precursor peptide is modified posttranslationally to introduce these novel amino acids. These processes transform a 57-mer produced by ribosomal synthesis into the final peptide. The didehydro amino acids are the source of the unsaturated amino acids, and the numerous thioether bridges are produced by the enzyme-catalyzed addition of cysteine residues to the didehydro amino acids.

Polycyclic peptide has a connection to subtilin and epidermin. All belong to a group of chemicals called lantibiotics. Polycyclic peptide is not chemically created; rather, it is produced in the food industry by cultivating L. lactis on natural substrates like milk or dextrose. Nisin is a rare example of a "broad-spectrum" bacteriocin that is effective against many Gram-positive organisms, including lactic acid bacteria (commonly associated to prevent food spoilage), Listeria monocytogenes (a known pathogen), Staphylococcus aureus, Bacillus cereus, Clostridium botulinum, etc.

The supply chain of the international Nisin Market was also disrupted by the restrictions on the movement of goods and transportation services.

Polycyclic peptide dissolves in water and has a parts-per-billion range of effectiveness. Polycyclic peptide concentration can be determined by a variety of methods, including chromatography and a straightforward agar diffusion bioassay. Most bacteriocins typically only inhibit closely related species, but this is not always the case. Additionally, spores are particularly well-repelled by it.

Gram-negative bacteria are shielded by their outer membrane, but after a heat shock or when this is combined with the chelator, they may become vulnerable to the action of polycyclic peptide. Polycyclic peptide has the capacity to inhibit Salmonella enterica and E. coli O157:H7 when combined with EDTA. Nisin, a class I bacteriocin, is more heat stable at lower pHs and is particularly stable at acidic pHs. Polycyclic peptide works by dissipating the membrane potential and pH gradient in pathogens like L. monocytogenes.