Green Synthesis and Biological Evaluation of Cerium Oxide Nanoparticles Using Saccharomyces boulardii with Potent Anti-Candida Activity

The synthesis of metallic and semiconductor nanoparticles through physical and chemical methods is well established; however, biological synthesis approaches are increasingly gaining attention due to their simplicity, cost-effectiveness, and eco-friendly nature. In the present study, cerium oxide nanoparticles (CeO₂-NPs) were synthesized using an aqueous solution of cerium salts mediated by the yeast Saccharomyces boulardii. This probiotic microorganism grows rapidly, is easy to cultivate on an industrial scale, and serves as an efficient biological system for nanoparticle biosynthesis. The obtained CeO₂-NPs exhibited an average particle size of approximately 62.54 nm, a zeta potential of of roughly –45 mV, and inhibition zone diameters ranging from (24.6 ± 1.1) to (11.2 ± 0.8) mm at 1000 and 62.5 mg/mL against tested Candida spp.The synthesized CeO₂-NPs were characterized using various analytical techniques, including Scanning Electron Microscopy (SEM), Field Emission Scanning Electron Microscopy (FESEM), Energy-Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD), to determine their size, morphology, and structural properties. The use of S. boulardii as a biogenic mediator demonstrates a sustainable and scalable approach for producing metal oxide nanoparticles. Furthermore, CeO₂-NPs exhibit promising antibacterial and antifungal properties, making them suitable for biomedical and tissue engineering applications requiring infection control. Overall, the study demonstrates that biologically synthesized CeO₂-NPs possess significant antimicrobial potential suitable for biomedical applications.