Antibacterial and antifungal activities of protease loaded modified thermoplastic starch blown PBAT films for active packaging

Abstract

Incorporation of proteolytic enzymes, such as papain and bromelain, into films possibly enhance their antimicrobial activity, thereby enabling the development of active food packaging. This study investigated enzymatic antimicrobial films for sustainable food packaging, specifically focusing on poly(butylene adipate-co-terephthalate)/acetylated (AS) and hydroxylated (HS) thermoplastic starch (PBAT/TPS) films incorporating papain, bromelain, and their combination. Fourier-transform infrared (FTIR) spectroscopy analysis revealed that enzyme incorporation did not significantly modify the chemical structure of the PBAT/TPS matrix; however, it influenced the crystallinity and the amorphous regions of the films. Papain enhanced the homogeneity of the films, whereas the effect of bromelain was dependent on the starch type employed. The incorporation of enzymes resulted in a decrease in tensile strength accompanied by an increase in elongation at break, indicating a plasticizing effect. All films exhibited hydrophilic characteristics. The incorporation of papain improved the water vapor and oxygen barrier properties. Enzymatic treatment modulated light transmission, with bromelain decreasing and papain increasing light permeability in PBAT/AS films. Bromelain exhibited greater efficacy against Escherichia coli, while the Papain/Bromelain blend enhanced antimicrobial activity against both Bacillus cereus and E. coli. Papain treatment resulted in delayed growth of Aspergillus niger, whereas Penicillium sp. remained unaffected. These findings indicate that the incorporation of enzymes altered the structural and functional properties of PBAT/TPS films, highlighting their potential utility in active food packaging applications.