Nisin:Carboxymethylcellulose polyion complex (PIC) nanoparticles. Preparation and antimicrobial activity

Nisin is a cationic antimicrobial peptide used as a natural food preservative against gram-positive bacteria. However, nisin is degraded following interaction with food components. Here, we report the first use of Carboxymethylcellulose (CMC), a versatile and affordable food additive, to protect nisin and extend its antimicrobial activity. First, we optimized the methodology by considering the effect of nisin:CMC ratio, pH, and, especially, the degree of substitution of CMC. In particular, we show here how these parameters affected the size, charge, and, notably, the encapsulation efficiency of these nanomaterials. This way, optimized formulations contained over 60 % w/w in nisin while encapsulating similar to 90 % of the nisin used. We then show that these new nanomaterials inhibited the growth of Staphylococcus aureus, a major foodborne pathogen, using milk as a representative food matrix. Remarkably, this inhibitory effect was observed with one-tenth of the concentration of nisin currently used in dairy products. We believe that the combination of the affordability of CMC, flexibility and simplicity of preparation, and the ability to inhibit the growth of food pathogens, makes these nisin:CMC PIC nanoparticles an ideal platform to underpin new nisin formulations.

Automated summary

This study demonstrates the use of Carboxymethylcellulose (CMC) as a protective agent to enhance the antimicrobial activity of nisin, a natural food preservative. The optimized nisin:CMC nanoparticles achieved high encapsulation efficiency (>90%) and maintained a nisin content of over 60% w/w. These nanoparticles effectively inhibited the growth of Staphylococcus aureus in milk at one-tenth of the concentration currently used in dairy products. The affordability, simplicity of preparation, and ability to control foodborne pathogens make nisin:CMC PIC nanoparticles a promising platform for developing new nisin formulations.