Antimicrobial Potential of Biosynthesized Zinc Oxide Nanoparticles Using Banana Peel and Date Seeds Extracts

In the present study, zinc oxide nanoparticles (ZnONPs) were eco-friendly synthesized using banana peel (BPE) and date seed (DSE) extracts. Biosynthesis of both ZnONPs_BPE and ZnONPs_DSE was confirmed by using an ultraviolet-visible spectrophotometer (UV-VIS), then followed by their characterization using different analyses: scanning (SEM), transmission electron microscope (TEM), zeta potential analysis, X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy. The antimicrobial potency of ZnONPs_BPE and ZnONPs_DSE was evaluated using a broth microdilution assay against pathogenic strains to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). UV spectra confirm the formation of ZnONPs-BPE (290 nm) and ZnONP_DSE (400 nm). TEM, SEM, and XRD revealed their hexagonal crystalline structures with nanoscale size ZnONPs_BPE (57.4 +/- 13.8 nm, -9.62 mV) and ZnONPs_DSE (72.6 +/- 17.1 nm, -5.69 mV). FTIR analysis demonstrated the presence of various functional groups on ZnONPs' surfaces that act as reducing, capping, and stabilizing agents. The biosynthesized ZnONPs demonstrated a good antimicrobial potential against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Salmonella enteritidis) strains. Especially, ZnONPs-BPE has a higher antimicrobial effect against Salmonella enteritidis (MIC = 0.75 mg/mL, MBC = 1.5 mg/mL), while ZnONP_DSE has a higher effect against Staphylococcus aureus (MIC = 0.75 mg/mL, MBC = 3 mg/mL). The present results are consistent with previous studies that reported the antimicrobial potential of green ZnONPs through ROS induction that in turn damages microbial DNA. Consequently, the present results support the use of different biowastes in NPs' synthesis, which is a simple and sustainable way that helps with waste management and decreases environmental pollution.