Mycosynthesis of Size-Controlled Silver Nanoparticles through Optimization of Process Variables by Response Surface Methodology

The present study was carried out to reduce the size of silver nanoparticles (AgNPs) by optimizing physico-chemical conditions of the Aspergillus fumigatus BTCB10 growth based on central composite design (CCD) through response surface methodology (RSM). Variables such as a concentration of silver nitrate (mM), NaCl (%) and the wet weight of biomass (g) were controlled to produce spherical, monodispersed particles of 33.23 nm size, observing 78.7% reduction in size as compared to the initially obtained size that was equal to 356 nm. The obtained AgNPs exhibited negative zeta potential of –9.91 mV with a peak at 420 nm in the UV-Vis range whereas Fourier Transform Infrared (FT-IR) analysis identified O–H, C = C, C ≡ C, C–Br and C–Cl groups attached as capping agents. After conducting RSM experiments, a high nitrate reductase activity value of 179.15 nmol/h/ml was obtained; thus indicating a likely correlation between enzyme production and AgNPs synthesis. The F-value (significant at 3.91), non-significant lack of fit and determination coefficient (R² = 0.7786) is representative of the good relation between the predicted values of response. We conclude that CCD is an effective tool in obtaining significant results of high quality and efficiency.