Process optimization for biogenesis of silver nanoparticles from Aspergillus flavus GGRK1 culture filtrate: Characterization and Its antibacterial efficacy

The cell-free culture filtrate (CF) of Aspergillus flavus GGRK1 could mediate the synthesis of silver nanoparticles using silver nitrate. Extracellular extract of Aspergillus flavus GGRK1 was a significant reductant for the reduction of silver nanoparticles due to presence of metabolites or other bioactive compounds. After the reduction of Ag (I) ions to Ag by the fungal CF, a dark brown color was obtained which indicated the biosynthesis of AgNPs. The maximum AgNPs were synthesized at the CCD-optimized condition of AgNO3 conc. of 4.189 mM, CFC 0.905 mL, and reaction time 8.17 h. The biosynthesized AgNPs had a zeta size of 119.4 nm diameter. The FTIR study revealed the significant efficacy of functional groups associated with the biosynthesized AgNPs. Additionally, the XRD study revealed a crystalline nature of biosynthesized AgNPs along very good correlation with FCC lattice. The biosynthesized nanoparticles showed significant antibacterial activity against gram-positive and gram-negative bacteria. As a result, the maximum ZOI was obtained at 150 µl/ml against all the tested organisms such as B. subtilis MTCC 121, S. aureus MTCC 96, E coli MTCC 443 and P. aeruginosa MTCC 424 with 18 mm, 20 mm, 14 mm, and 18 mm, respectively.