Multifunctional biodegradable films of caffeic acid-grafted succinoglycan and polyvinyl alcohol with enhanced antioxidant, antibacterial, and UV-shielding properties.

This study emphasizes the growing demand for functional and eco-friendly biopolymers across various industries driven by the need for safer and sustainable materials. To meet this demand, a novel biopolymer named caffeic acid-grafted succinoglycan (Ca-SG) was successfully synthesized by grafting caffeic acid (Ca) onto microbial succinoglycan (SG), with the structure confirmed through H NMR and FTIR spectroscopy. The grafting process significantly improved the thermal stability and rheological behavior of Ca-SG, while imparting strong antibacterial activity against E. coli (92.1 %) and S. aureus (98.4 %), and high antioxidant capacity (63.6 % DPPH, 93.7 % ABTS). Ca-SG was then incorporated into polyvinyl alcohol (PVA) to form composite films via solvent casting. These films retained the bioactivities of Ca-SG, showing sustained antioxidant effects (63.8 % DPPH, 92.9 % ABTS) and antibacterial efficacy against E. coli (98.8 %) and S. aureus (87.8 %). It was also demonstrated excellent UV-shielding capacity of approximately 99.9 %, combined with recyclability and biodegradability. A practical blueberry preservation test validated suitability of the film for food packaging applications. Overall, the multifunctional characteristics of the PVA/Ca-SG films, including antioxidant, antibacterial, and UV-blocking activities, suggest a broad potential for applications in food packaging, cosmetics, pharmaceuticals, and environmentally-friendly materials.