Bioactive Bacterial Cellulose Films Functionalized with Pecan Nutshell [Carya illinoinensis (Wangenh) K. Koch] Extract and Glycerol: Physicochemical, Thermal, and Antibacterial Properties

Abstract

Valorizing agro-industrial by-products as feedstocks for coatings and biomaterials offers a sustainable route to value-added materials. This study investigated the effects of pecan nutshell extract (PNSE) and glycerol on the physicochemical, bioactive, and antibacterial properties of functionalized bacterial cellulose (BC) films. PNSE showed a high phenolic and flavonoid content and substantial antioxidant capacity (DPPH, ABTS, and FRAP). BC-based films containing PNSE and glycerol were subsequently characterized by FTIR, SEM, TGA/DTG, and DSC, and their antibacterial activity was evaluated by disk diffusion against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 35218, and Salmonella typhimurium ATCC 14028. The extract contained 742.91 ± 4.04 mg GAE/g of total phenolic compounds, 82.42 ± 0.67 mg CE/g of flavonoids, and 475.13 ± 2.84 µmol TE/g in the DPPH assay. ATR-FTIR revealed spectral changes consistent with interactions among cellulose hydroxyl groups, glycerol, and phenolic constituents of PNSE. SEM revealed changes in surface morphology, and TGA/DTG recorded degradation temperatures of up to 386 °C. The BC-PNSE-GC-4 formulation exhibited the strongest antibacterial activity against S. aureus, demonstrating an inhibition zone of 18 mm. The developed films show promising potential for use in active food packaging applications.