Filamentous Fungi Based Synthesis Of Silver Nanoparticle, Characterization And Evaluation Of Its Antibacterial Activities At Ambo University, West Shewa Zone Of Oromia Regional State

Abstract

Fungi are increasingly recognized for their ability to synthesize metal nanoparticles, offering eco-friendly and sustainable alternatives to physical synthesis methods.This research aimed to isolate and characterize soil fungi and evaluate their potential for silver nanoparticle synthesis and antimicrobial activity. Soil samples were cultured on Potato Dextrose Agar (PDA) and Malt Extract Agar (MEA), yielding 46 fungal isolates, from which 6 were selected for further analysis. Among these, isolates S3i10, S3i11, S7i31, S3i9 and S5i19 as Aspergillus species, and S8i36 as Fusarium species, based on their distinct physical characteristics. Fungal biomass and filtrates were used to synthesize silver nanoparticles by adding 1 gram of biomass to 35 ml of 0.1 M silver nitrate solution and 1 ml of filtrate to another 35 ml of the same solution. These nanoparticles were then tested for antimicrobial activity. Notably, filtrate-based synthesis using isolate S3i11 exhibited superior antimicrobial activity against Salmonella, with a 20 mm inhibition zone compared to the 14 mm zone of the positive control. Biomass-based synthesis from S3i11 demonstrated enhanced efficacy against Staphylococcus aureus, with an 18 mm inhibition zone, surpassing the 16 mm inhibition zone observed against Salmonella Sps. X-ray diffraction (XRD) analysis provided insights into the crystallographic properties of the synthesized nanoparticles. Sample S3_19 showed high crystallinity, small particle size, uniform diffraction peaks, and high purity, outperforming other samples such as S7_I13, S5_I19, and S3_I10 in the 20–40° 2Theta range. Transmission data further revealed that nanoparticles in sample S3_I9 exhibited high transmittance of 90% in the infrared spectrum, indicating low absorption in this region, which may be due to a low concentration of absorbing species. Additionally, absorbance spectra in the ultraviolet-visible (UV-Vis) range showed high peaks between 200 and 300 nm with an absorbance of 3 in samples S3i11, S5i19, and S7i31. This suggests strong light- absorbing properties, possibly due to surface plasmon resonance or bandgap transitions. Overall, the study highlights the potential of fungal isolates in nanoparticle synthesis and their promising antimicrobial properties, particularly against drug-resistant pathogens. These findings provide a foundation for further exploration into the use of fungi in nanotechnology and antimicrobial therapies