Investigating the Potential of Green-Fabricated Zinc Oxide Nanoparticles to Inhibit the Foodborne Pathogenic Bacteria Isolated from Spoiled Fruits

In the current investigation, the antibacterial activity of zinc oxide nanoparticles (ZnO-NPs) formed by an aqueous extract of Psidium guajava leaves against foodborne pathogenic bacterial strains was investigated. To achieve this goal, 33 bacterial isolates were obtained from spoiled fruits. Among these isolates, 79% showed cellulase activity, 82% showed amylase activity, 81% exhibited xylanase potential, and 65% exhibited lipase activity. Moreover, 12 isolates showed complete hemolysis (β-hemolysis). The identification of these isolates was done using sequencing and amplification of 16s rRNA as Staphylococcus aureus (two strains), Pseudomonas syringae (one strain), E. coli (two strains), Salmonella typhimurium (two strains), Listeria monocytogenes (one isolate), Bacillus cereus (two isolates), and Bacillus subtilis (two isolates). The formed ZnO-NPs by aqueous Psidium guajava leaf extract were characterized using UV, FT-IR, TEM, EDX, XRD, DLS, and Zeta potential. The data revealed the successful formation of a spherical shape, crystallographic structure, and well-arranged ZnO-NPs. FT-IR showed the effect of different functional groups in the plant extract in the formation of ZnO-NPs through reducing, capping, and stabilizing of end products. Moreover, EDX analysis showed that the Zn ion occupied the main component of the produced NPs. Interestingly, the obtained bacterial strains showed varied sensitivity toward green-synthesized ZnO-NPs. The growth inhibition of foodborne pathogenic strains by ZnO-NPs was concentration dependent, forming a zone of inhibition in the range of 20–23 mm at a concentration of 200 µg mL−1, which decreased to 15–18 mm at 100 µg mL−1. Moreover, the values of MIC were 25 and 50 µg mL−1 based on the bacterial strain. Overall, the green-synthesized ZnO-NPs can be a useful approach for inhibiting the growth of spoilage bacterial strains that destroy fruits and hence reduce the harmful effects of traditional treatment methods on the environment and human health.