Comparative Studies on Antibacterial Potentials of Biosynthesized Cerium Oxide and Zinc Oxide Nanoparticles Against Fish Pathogens

Plant-mediated synthesis of nanoparticles has gained significant attention due to its eco-friendliness, non-toxic nature, ease of preparation, and biocompatibility. Likewise, phytochemicals have been recognized as effective bio-reductants and capping agents in the formation of nanoparticles. The aim of this study was to compare the antibacterial potentials of biosynthesized cerium oxide and zinc oxide nanoparticles (CeO₂NPs and ZnONPs) against selected fish pathogens, Aeromonas hydrophila, Aeromonas schubertii, Bacillus subtilis, Bacillus cereus, and Klebsiella pneumoniae. Qualitative analysis of Carica papaya leaf extract was conducted to examine the biomolecules present, followed by the biosynthesis of the nanoparticles. The obtained CeO₂NPs and ZnONPs were characterized through UV-visible spectrophotometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy to confirm the formation of the nanoparticles. The results showed that CeO₂NPs had a spherical shape with an average size of 46.34nm, while ZnONPs exhibited a cylindrical shape with an average size of 43.77nm. Antibacterial sensitivity tests (AST) indicated that ZnONPs had greater antibacterial potential than CeO₂NPs against A. hydrophila (0.00 and 13.00 ± 1.15mm), A. schubertii (16.50 ± 1.73 and 15.50 ± 0.58mm), B. cereus (0.00 and 17.00 ± 1.15mm), and K. pneumoniae (13.00 ± 1.15 and 16.50 ± 0.58mm). However, CeO₂NPs were more effective against B. subtilis than ZnONPs (12.00 ± 1.15 and 13.00 ± 1.15mm). Both nanoparticles showed significant differences in their AST values against A. hydrophila, B. cereus, and K. pneumoniae (P< 0.05), while no significant difference was observed against A. schubertii and B. subtilis. Based on these findings, it can be concluded that ZnONPs are more effective than CeO₂NPs against A. hydrophila, B. cereus, and K. pneumoniae, and therefore may be useful in treating fish diseases caused by these pathogens.