Nisin anchored cellulose nanofibers for long term antimicrobial active food packaging

Increasing consumer demand for high performance bio-based materials in order to develop microbiologically safer foods has forced the food industry to revise their packaging strategies. One of the emerging fields within this industry is active packaging which prevents an excess of antimicrobials in food formulation and, meanwhile, inhibits or reduces bacterial growth. In this study, a green process of immobilizing a peptide on bio-based carboxylated cellulose nanofibers (CNF) using a coupling agent has been proposed. Validity of the grafting reaction between nanocellulose, the coupling agent and peptide was first analyzed by Quartz crystal microbalance-dissipation (QCM-D). Efficiency of the grafting reaction was characterized with Fourier Transform Infrared spectroscopy and thermogravimetric analysis which suggest the grafting of nisin on CNF. Finally, the amount of grafted nisin was quantified on the surface of CNF by conductometric titration and nitrogen content analysis. The antimicrobial activity and release experiment demonstrated that the nisin grafted CNF displayed excellent antimicrobial activity against different Gram +ve bacteria (Bacillus subtilis and Staphylococcus aureus) with significant 3.5 log reduction. The obtained results are promising and confirm the interest in such strategy.