Development and characterization of EPS-modified alginate films with improved barrier, antioxidant, antimicrobial,...

Functionally enriched calcium alginate (CA/EPS) biocomposite films incorporating exopolysaccharide (EPS) from Bacillus licheniformis WL5 were developed to delay enzymatic browning in fresh produce. FT-IR analysis confirmed strong hydrogen bonding between EPS and alginate, whereas SEM revealed a denser, fibrillar structure. Compared with neat CA films, CA/EPS films had a reduced moisture content (7.00%), solubility (21.9%), swelling ratio (35.83%), and water vapor transmission rate (23.53 g/m²·day), indicating improved barrier properties. Mechanical testing revealed higher tensile strength and Young's modulus, whereas optical studies demonstrated increased opacity and improved UV-Vis light protection. The films exhibited strong antioxidant activity (DPPH 90.19%, ABTS 92.40%) and notable antimicrobial activity against Staphylococcus aureus and Escherichia coli, with lower MIC and MBC values. Controlled diffusion-based release of bioactive compounds was observed. Coating fresh-cut apples effectively reduced browning during cold storage, and strong polyphenol oxidase inhibition (IC₅₀ = 17.72 μg/mL) highlighted their potential as multifunctional active packaging materials.