Rodrigo Cáceres

This study investigates the development of polyvinyl alcohol (PVA)-based nanocomposite films reinforced with cellulose nanofibrils (CNFs) and biobased additives derived from blueberry pruning waste for sustainable food packaging applications. The nanocomposites were fabricated via solvent casting and evaluated in terms of their thermal and antimicrobial properties. Thermogravimetric analysis (TGA/DTG) revealed that the thermal degradation of the nanocomposites occurs through overlapping processes of PVA and CNFs, with maximum degradation temperatures ranging from 273 to 293 °C depending on the formulation. The incorporation of CNFs modified the degradation pathway and promoted the formation of thermally stable carbonaceous residues, while TEMPO-oxidized samples exhibited a decrease in degradation onset (14–24 °C) due to the presence of oxidized surface groups. Remarkably, the nanocomposites exhibited significant antimicrobial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria without the incorporation of external antimicrobial agents. Bleached PVA/CNFs films achieved complete growth inhibition (100%), while lignin-containing and additive-modified systems showed selective antibacterial behavior. Zeta potential analysis confirmed a negatively charged CNF surface (−35.3 mV), which may contribute to electrostatic interactions with bacterial membranes. Scanning electron microscopy (SEM) revealed nanostructured surfaces with exposed fibrillar networks that promote bacterial adhesion and immobilization, supporting a contact-active antimicrobial mechanism. These findings demonstrate that the antimicrobial performance of PVA/CNFs nanocomposites is governed by intrinsic physicochemical and topographical properties rather than by the release of antimicrobial agents. This approach provides a safer and more sustainable strategy for the design of active food packaging materials.

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.

Bacterial nanocellulose (BNC) is a highly pure biopolymer with promising applications in the biomedical, food, and textile industries. However, the high production costs and low yields obtained in static conditions limit its scalability and industrial applications. This study addresses the sustainable production of BNC using a rotary disk bioreactor (RDB) and explores the use of grape pomace extract as an alternative carbon source for BNC production. Parameters such as the BNC production and biomass yield were evaluated using Komagataeibacter xylinus ATCC 53524 under different operational conditions (disk surface, rotation speed, and number of disks). The results showed that cellulose production increased using silicone-coated disks at 7–9 rpm (up to 2.72 g L⁻¹), while higher yields (5.23 g L⁻¹) were achieved when using grape pomace extract as the culture medium in comparison with conventional HS medium. FTIR and TGA characterizations confirmed that BNC obtained with grape pomace extract presents the same thermal and chemical characteristics than BNC produced with HS medium. This work provides insight into the feasibility of upscaling BNC production using a bioprocessing strategy, combining production in the RDB system and the use of an agro-industrial waste as a sustainable and cost-effective alternative.