Antibacterial Effect of Biosynthesized Zinc Oxide Nanoparticles against Erwinia amylovora and Induction of Crop Growth

Objectives: Zinc oxide nanoparticles (ZnO-NPs) are widely recognized as one of the most promising types of materials in a wide range of applications, including agriculture. Modern systemic efforts have identified several therapeutically active microalgae-derived compounds, including phenols, flavonoids and others. The antibacterial properties of the phenolic substances were demonstrated. Hence, the present study aims to exhibit the antibacterial activity of the bioactive compound capped silver nanoparticles under in vitro conditions.

Methods: Bioactive compound separated by Solid-phase Extraction method. Dispersible Zinc oxide nanoparticles synthesized using the bioactive compound as the major capping agent. Zinc nitrate was used as starting material and its reduction was carried by phenolic components of Spirulina platensis aqueous extract from Zn2+ to ZnO. The synthesized Zinc oxide nanoparticles are characterized by H1 NMR spectroscopy. Conjugated nanoparticles are characterized physically by Scanning Electron Microscopy (SEM) analysis. SEM demonstrated particle sizes in the range 10–15 nm. ZnO nanoparticles demonstrated antibacterial activity against an isolated plant pathogen Erwinia amylovora. Time kill determination assay was done.

Findings: Phenols obtained after Solid Phase Extraction. Hence, this was regarded as the maximum quantified bioactive compound of Spirulina platensis. H1 NMR spectroscopy analyses showed the presence of phenolic compounds and alcohols groups of long chain were also detected. In SEM analysis, the mean diameter of spherical Phenols-ZnOPs is less than 15 nm surrounded by the capping agent. In given time periods of 4, 8, 16, and 24 hour cells, concentrations of 1000µg/mL were 42 %, 33 %, 20 %, and 18 %. At 500 µg/mL of extract concentration, Spirulina platensis inhibited 50% bacterial proliferation (IC50) of Erwinia amylovora. A significant inhibitory effect (p<0.0001) was seen against the plant pathogenic strain.

Novelty: In addition to their antibacterial activities, biosynthesized ZnO-NPs are thought to show promise efficacy as growth accelerators. The most dangerous bacterial disease of pear and apple trees is fire blight, caused by Erwinia amylovora. Phenolic capped ZnO-NPs have been found to be efficient plant pathogen antagonists.