Antimicrobial Effect of Cellulose Nanofibrils (CNFs) and Biobased Additives in Polyvinyl Alcohol Nanocomposite Materials for Sustainable Food Packaging Application

This study evaluates the antimicrobial properties of nanocomposite materials based on polyvinyl alcohol (PVA) reinforced with cellulose nanofibrils (CNFs) and/or supplement-ed with biobased additives derived from blueberry pruning wastes, with the objective of developing biodegradable food packaging systems with antimicrobial properties. The nanocomposites were prepared using a solvent-casting processing approach, and their thermal, physicochemical, and antimicrobial properties were assessed. All the nanocomposites exhibited thermal stability up to 200 °C, confirming their suitabil-ity for conventional food packaging processing conditions. Antimicrobial activity tests re-vealed inhibitory effects against both Gram-positive and Gram-negative bacteria. Bleached PVA/CNFs films showed complete growth inhibition (100%) against E. coli and S. aureus. In contrast, unbleached PVA/CNFs and PVA/CNFsB supplemented with blueber-ry-derived additives exhibited selective inhibition against E. coli, highlighting the influ-ence of nanofibril composition and additive incorporation on antimicrobial performance. Zeta potential measurements revealed values of –35.3 mV for the CNFs, confirming their negatively charged surface, which may contribute to interactions with bacterial mem-branes. Additionally, scanning electron microscopy (SEM) showed that the incorporation of CNFs generates nanostructured surfaces with exposed fibrillar domains, where bacteri-al cells become adhered and immobilized. These topographical features suggest that the antimicrobial behavior of the nanocomposites is associated with direct bacteria–surface interactions, supporting a contact-active antimicrobial behavior associated with the CNFs.