Biodegradable PLA films plasticized with hydrophobic deep eutectic solvents and enriched with green-synthesized ZnO nanoparticles from date palm pits for antimicrobial food packaging

This study presents the development of biodegradable polylactic acid (PLA)-based films enriched with green-synthesized zinc oxide nanoparticles (ZnO NPs) for potential application in active food packaging. The ZnO NPs were synthesized using an aqueous extract of date palm pits, valorizing agro-industrial waste as a sustainable precursor. The films were prepared via solvent casting, incorporating 5 wt% of a hydrophobic deep eutectic solvent (DES) as a plasticizer and varying ZnO NP concentrations (1–4 wt%). Morphological and structural analyses (SEM, XRD) confirmed homogeneous dispersion of both DES and ZnO NPs in the PLA matrix. The incorporation of these additives improved tensile strength while reducing elongation at break, and moderately increased opacity and water vapor permeability. Notably, the films demonstrated exceptional effectiveness with the total inhibition of Bacillus cereus , a challenging spore-forming pathogen, alongside reductions of 1.4 ± 0.05 Log CFU/mL for Staphylococcus aureus and 8.2 ± 0.35 Log CFU/mL for Escherichia coli after 24 h. These results highlight the potential of PLA/DES/ZnO nanocomposites as sustainable and effective materials for antimicrobial food packaging.