Synthesis, Characterization and Antifungal Efficacy of Silver Nanoparticles against Fungi isolated from Animal Feed Crop Residues

Abstract

Fungal contamination poses serious health risks to both human and livestock which lead to significant economic losses. Fungi such as Aspergillus, Penicillium, and Fusarium species not only reduce feed quality but also produce harmful mycotoxins. Therefore, this study aim to synthesized and characterize silver nanoparticles with its antifungal efficacy against fungi isolates from animal feed crop residues. Plate dilution and microscopic method was use to screened and identified the fungi contaminate in four selected crop residues. While silver nanoparticles (AgNPs) were synthesis through green approach and characterized through Ultraviolet-visible spectroscopy (UV), Dynamic Light Scattering (DLS), X-ray diffraction (XRD) and High-Resolution Transmission Electron Microscope (HRTEM). Mycelia growth inhibition method was use for the fungal inhibition activities of silver nanoparticles. The groundnut haulms (GH) had the highest fungal load of 470 x10² CFU/g, among the crop residues studied followed by GH 97 x10² CFU/g, then BH 74 x 10² CFU/g and MO had the least 27 x 10² CFU/g. A total of 40 fungal isolates were identified, in which Aspergillus niger 8(20.0%), Aspergillus flavus 5(12.5) and Penicillium species 7 (17.5%) are known to be toxigenic orgnisms. UV- visible spectroscopy confirmed surface plasmon resonance of the AgNps at 420.20 nm with Z-average diameter of 37.60 nm and a Polydispersity Index (PDI) of 0.286. X-ray diffraction (XRD) analysis revealed crystalline nature of AgNps with average crystalline size of 22.53 nm. While, HRTEM and SAED analyses confirmed that synthesis route is effective with circular shape. The SAED showed a visible lattice fringes at different orientations and well-separated diffraction rings are perfect indicators of the FCC-structured silver formation. While EDX analysis also confirmed the production of silver nanoparticles.  The synthesized silver nanoparticles exhibited daily increase antifungal activity, with inhibition across the fungal isolates ranging from 27.58% of Day 1 to a peak of 89.94% by Day 5, before declining for Day 7. It can be inferred from various analysis conducted that the biosynthesized silver nanoparticles exhibit strong antifungal potential of day dependent that can serve as an alternative to conventional chemical preservatives in feed storage.

Keywords: Silver nanoparticles, fungal inhibition, feed contamination, XRD, HRTEM, GH