Hybrid levan-Ag/AgCl nanoparticles produced by UV-irradiation: properties, antibacterial efficiency and application in bioactive poly(vinyl alcohol) films

Foodborne diseases caused by resistance of microorganisms to multiple antimicrobial agents have emerged as a major public health concern around the world. The search for potential antimicrobials has resulted in the emergence of metal nanoparticles for protection against these infections. In this study an eco-friendly and green approach was used to biosynthesize hybrid Ag/AgCl nanoparticles (NPs), using levan from Bacillus mojavensis as a stabilizing/reducing agent, with a high efficiency against a broad spectrum of foodborne bacteria as well as biofilm formations. The morphology and physicochemical characteristics of levan-Ag/AgCl NPs were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis spectroscopy (UV), dynamic light scattering (DLS) and thermogravimetric analysis (TGA). The hybrid levan-Ag/AgCl was evaluated for antibacterial activity against foodborne pathogenic bacteria (Escherichia coli, Klebsiella pneumoniae, Salmonella enterica, Pseudomonas aeruginosa, Staphylococcus aureus, Micrococcus luteus, Listeria monocytogenes, Enterococcus faecalis, Bacillus subtilis and Bacillus thuringiensis). The study demonstrated the strong efficiency of hybrid levan-Ag/AgCl NPs as a potent inhibitor against all tested strains, with much higher activity against Gram-negative than Gram-positive bacteria. Furthermore, bacterial strains were found to be highly sensitive to hybrid levan-Ag/AgCl NPs in comparison to the tested antibiotics. As a possible application of levan-Ag/AgCl NPs as an additive in packaging, PVA films with different amounts of hybrid levan-Ag/AgCl NPs were prepared by casting and their antibacterial, mechanical, and optical properties and ability to expand the shelf life of beef meat were explored. Interestingly, the amount of Ag leached out from films was below the permissible limit. This work demonstrates the strong antibacterial action of hybrid levan-Ag/AgCl NPs and their potential use in bioactive packaging material.