The Application of Nisin in Seafood Preservation

Nisin is an antimicrobial peptide produced by Lactococcus lactis that exhibits broad-spectrum bacteriostatic activity against Gram-positive bacteria, effectively inhibiting the growth of Listeria. It is commonly used in seafood preservation. The following are relevant case studies:

Application in Cold-Smoked Salmon

Cold-smoked salmon is a ready-to-eat food that is prone to Listeria contamination under refrigeration. In one study, three Listeria strains were pre-cultured in sublethal concentrations of benzalkonium chloride, then inoculated onto salmon fillets (inoculum size: approximately 10² CFU/g). The fillets were pre-treated with 0, 25, or 250 ppm of Nisin, followed by vacuum packaging and incubation at 4°C or 7°C for 30 days. Results showed that the bacteriostatic effect was concentration-dependent: 250 ppm Nisin reduced the prevalence of Listeria, with no influence from storage temperature or serotype. Additionally, at 7°C or with 25 ppm Nisin treatment, the serotype 1/2b strain was more sensitive to Nisin than serotypes 1/2a and 4b.

Application in Other Seafood

Studies have found that Nisin significantly inhibits Gram-positive bacteria such as Listeria in high-moisture baked shrimp. When added at levels above 20 mg/kg, the inhibition rate reaches 100%, and it also extends the shelf life. Furthermore, Fang Shiyuan et al. used a composite preservative containing 5.92% sodium lactate, 0.04% Nisin, and 1.06% sodium alginate to treat turbot stored at 4°C, extending its shelf life to 14 days.

The mechanism by which Nisin inhibits Listeria involves recognizing and binding to lipid II in the bacterial cell membrane, using it as a "docking molecule" to efficiently assemble and form pores. This leads to the dissipation of proton motive force and inhibits bacterial cell wall synthesis, thereby exerting bacteriostatic effects. Moreover, Nisin is a safe, non-toxic natural preservative. It is currently the only bacteriocin permitted as a food additive worldwide and has been included in China’s national food safety standards, making it suitable for use in seafood preservation and other food-related fields.