Sustainable formulations made of a furan-based copolyester and nisin for flexible antimicrobial packaging applications

INTRODUCTION

The growing concern over environmental impact caused by fossil-based plastics has intensified the search for sustainable alternatives, in particular in the field of food packaging, which is a short life-cycle application involving high volumes of plastics. Among bio-based polyesters, those containing 2,5-furandicarboxylic acid (FDCA) have emerged as promising candidates and green alternatives to the fossil-based terephthalic polyesters. Apart from their renewable origin, their success is due to their outstanding mechanical and barrier properties. However, they lack intrinsic antimicrobial features, which is a preferable requirement aiming to extend the shelf-life of food products, enhancing at the same time their safety.

METHODS

This work focuses on the realization of fully bio-based blends from a furan-based copolyester and a natural preservative to obtain novel solutions in the field of antimicrobial food packaging. Nisin, a polycyclic antibacterial peptide which can be isolated from Lactococcus lactis, was chosen as preservative, and mixed, in different weight amounts, with poly(butylene/pentamethylene furanoate), P(BPeF). The compression-moulded films where then deeply characterized.

RESULTS

The incorporation of nisin allowed for a modulation of mechanical flexibility and toughness, whilst retaining the thermal stability, which is one of the main advantages of the pristine polyester, as well as the main thermal transitions. Moreover, the excellent gas barrier properties of P(BPeF) were preserved. Lastly, the implementation of antibacterial features otherwise absent in the pristine polymer was obtained, as estimated by disc diffusion assay against L. Plantarum and L. Monocytogenes.

CONCLUSION

The films investigated in this work are valuable candidates for application in the field of flexible and active food packaging, and credible substitutes of currently used unsustainable materials for the fabrication of flexible, high-barrier containers.