Abstract
The growing demand for sustainable food packaging has encouraged the development of biodegradable materials with improved protective and functional properties. This study developed sodium alginate (ALG) composite films containing bacterial nanocellulose (BNC) and mycosporine-like amino acid (MAA)-rich extracts. The novelty lies in combining nanocellulose reinforcement with the valorization of marine-derived by-products in a multifunctional biodegradable packaging system. Films were produced by solution casting and evaluated for their structural, mechanical, surface, moisture-related, and barrier properties. Their effectiveness in preserving fresh blueberries was also assessed during four weeks of storage. BNC incorporation strengthened the alginate matrix, increasing tensile strength and reducing film porosity. The addition of MAA-rich extracts improved film flexibility and contributed functional properties. However, higher MAA concentrations increased film hydrophilicity, resulting in greater moisture content, water solubility, swelling, and rehydration capacity. Among the tested formulations, the ALG–BNC film containing 3% MAA showed the most balanced performance, combining low porosity, adequate tensile strength, improved flexibility, and controlled moisture behaviour. This formulation also provided the best preservation of blueberries, with the lowest weight loss of 3.6% after four weeks. The results demonstrate that film performance depends on balancing mechanical stability, flexibility, and water sensitivity. The synergistic combination of BNC and MAA-rich extracts offers a promising circular-economy strategy for producing sustainable food-packaging materials with improved functionality and potential for extending fresh-produce shelf life.