Extracellular synthesis of silver nanoparticles using cell-free culture extracts of Aspergillus niger QNUGT6 and evaluation of their antimicrobial activity

Abstract

Modern nanotechnology focuses on developing environmentally friendly methods for synthesizing nanomaterials. Among these, the biosynthesis of nanoparticles using biological microorganisms has emerged as a promising strategy. In this study, silver nanoparticles (AgNPs) were synthesized using the extracellular secretions of the fungus Aspergillus niger. The fungal strain was successfully isolated from rice wine yeast and identified as Aspergillus niger QNUGT6 based on morphological characterization and sequencing of the internal transcribed spacer (ITS) gene region. The formation of AgNPs was confirmed by a visible color change and the appearance of a characteristic surface plasmon resonance (SPR) band at 410 nm. X-ray diffraction (XRD) analysis revealed diffraction peaks corresponding to crystalline AgNPs. Fourier-transform infrared (FTIR) spectroscopy indicated the involvement of various functional groups in the culture medium responsible for the reduction of Ag⁺ ions to Ag⁰. Scanning electron microscopy (SEM) analysis confirmed that the synthesized AgNPs were spherical with an average size of 26.1 ± 7.8 nm. Moreover, the synthesized AgNPs exhibited inhibitory activity against Bacillus cereus bacterial pathogens. Thus, our study provides further evidence for the potential use of Aspergillus fungi to control the properties of AgNPs.

Keywords

antibacterial activity / Aspergillus niger / green synthesis / nanomaterial / silver nanoparticle

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