Antimicrobial Evaluation of Zinc Oxide Nanoparticles against Selected Pathogens of Dioscorea rotundata, L Tubers

Abstract

This research focuses on sustainable approaches to the synthesis of zinc oxide nanoparticles ( ZnO NPs) using Colocasia esculenta leaves extract and in vitro antimicrobial studies of the ZnO NPs against selected pathogens of Dioscorea rotundata, L tubers. ZnO NPs were synthesized by green route using aqueous leaves extract of Colocasia esculenta, L and characterized by UV-Visible (UV-vis), X-ray Diffraction ((XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) and Fourier Transform Infra-red (FTIR) spectroscopy.  The data obtained from the zone of inhibition (mm) was analyzed using statistical package for social science, SPSS Version 21. Results were represented as Mean ± Standard Deviation (SD). The difference between more than 2 groups of data was evaluated using one-way Analysis of Variance (ANOVA) with Least Significant Difference (LSD) post hoc test. Differences between means were considered significant at p < 0.05. The result revealed well segregated wurtzite hexagonal crystalline ZnO NPs with mean crystallite size of 16 nm, ranging from 14.15 nm - 17.12 nm. FTIR spectra of the extract and the biosynthesized ZnO NPs revealed phenolic groups as reductant of zinc ions and amines, peptides and amides groups as capping and stabilizing agents. The biosynthesized ZnO NPs exhibited enhanced antimicrobial action in a dose-dependent manner against five Dioscorea rotundata tubers pathogenic fungi: Aspergillus niger, Aspergillus flavus, Botryodioplodia theobromae, ,Phizopus stolenifera and Fusarium oxysporum as well as three bacteria: Klebsiella oxytoca, Serratia marcenscens and Pseudomonas aeruginosa. The biosynthesized ZnO NPs exhibited effective to moderately effective inhibition ranging from 71.45  to 17.45 % on the pure isolates. The ZnO NPs compared favourably with standard antifungal (Ketoconazole) and antibacterial (Ciprofloxacin) agents used as positive controls. The ZnO NPs holds great prospects in reducing postharvest Dioscorea rotudata, L tuber rot and may serve as source of green nanomaterials for antimicrobial drug formulation and development.