Upcycling Banana Peel for Sustainable ZnO Synthesis and Its Photocatalytic Effect of Pathogen Inactivation Combined with UVA Irradiation

Abstract This study investigated the green synthesis of zinc oxide nanoparticles (ZnO NPs) using banana peel extract (BPE), examining the impact of synthesis pH (8, 10, and 12) on nanoparticle characteristics and their photocatalytic inactivation efficacy. Optimal synthesis at pH 10 produced ZnO NPs with superior crystallinity, reduced structural defects, spherical morphology, and stable colloidal dispersion. Its photocatalytic effect was evaluated against foodborne pathogens, including Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes under UVA irradiation. ZnO NPs synthesized at pH 10 demonstrated the most effective bacterial effect, generating the highest levels of reactive oxygen species (ROS) compared to ZnO NPs synthesized at other pH levels. The combination of ZnO NPs and UVA irradiation resulted in significant bacterial membrane damage and intracellular ROS production, leading to cell death. Additionally, the ZnO NPs retained stable photocatalytic activity over multiple reuse cycles, emphasizing their potential for long-term applications. These findings demonstrate the potential of upcycling food waste, such as banana peel, into valuable photocatalysts for efficient bacterial inactivation. This green synthesis approach provides a sustainable and effective strategy for developing photocatalysts that enhance food safety and environmental sustainability.