Nisin

What is Nisin and how is it produced?

Nisin is a natural preservative, structurally composed of 34 amino acid residues with a molecular weight of 3500 Da. It belongs to a class of antimicrobial peptides known as lantibiotics and is primarily produced by certain strains of the bacterium Lactococcus lactis subsp. lactis during the exponential phase of growth.

How does Nisin work as an antimicrobial?

Nisin functions primarily against Gram-positive bacteria by targeting their peptidoglycan walls. While it is significantly effective against lactic acid bacteria and sporulated bacteria, it has lower activity against Gram-negative bacteria, molds, and yeasts due to the resistance provided by the outer membranes of these organisms. However, the addition of chelating agents like EDTA can enhance its efficacy against Gram-negative bacteria by destabilizing these membranes.

Are there different types of Nisin?

Yes, there are several natural variants of Nisin, namely Nisin A, Z, F, Q, U, and U2. These variants differ by up to 10 amino acids. Variants A, Z, F, and Q are produced by Lactococcus lactis, while Streptococcus species produce variants U and U2. Additionally, bioengineering approaches have been utilized to develop Nisin derivatives with improved activity, particularly against specific pathogens, including Gram-negative bacteria.

Is Nisin safe for human consumption?

Yes, Nisin is considered safe for human consumption. It is classified as "Generally Regarded as Safe" (GRAS) and has been accepted as a food preservative by the Codex Alimentarius. Studies have shown that Nisin is not carcinogenic or mutagenic, nor is it associated with reproductive or developmental toxicity. The oral lethal dose (LD50) of purified Nisin in rats is more than 2000 mg/kg body weight, and the LD50 for a Nisin preparation in mice is 6950 mg/kg body weight. The European Food Safety Authority (EFSA) has also confirmed that Nisin can be safely used at its established Acceptable Daily Intake (ADI) of 0.13 mg/kg body weight.

In which industries is Nisin typically used, and why?

Nisin is predominantly used in the food industry, especially in dairy products, as a preservative. Its ability to inhibit the growth of spoilage and pathogenic bacteria makes it valuable for extending the shelf life of food products and ensuring food safety.