Sporotrichum thermophile culture extract-mediated greener synthesis of silver nanoparticles: Eco-friendly functional group transformation and antibacterial study

Abstract Thermophilic mould Sporotrichum thermophile (BJLRMDU7) played the role in greener synthesis of the silver nanoparticles (AgNPs) extracellularly using silver nitrate. The change in colour from transparent to dark brown primarily indicated the formation of AgNPs due to reduction of Ag (I) ions to Ag by the fungal culture extract. Nanoparticles synthetic process was optimized by using “one variable at a time” approach. Sucrose containing medium having pH 8.0 supported the synthesis of AgNPs by the mould at 45 oC. Furthermore, presence of light significantly accelerated the formation of silver nanoparticles. AgNPs were characterized by various techniques like UV-vis & FT-IR spectroscopy, dynamic light scattering (DLS) and X-ray diffraction (XRD). Appearance of a band at 426 nm in UV-vis spectrum revealed the reduction of Ag(I) ions to Ag (0) by mould’s culture filtrate. DLS data showed that AgNPs bear an average size of 70 nm, while XRD data revealed particle size of 40 nm. The application of AgNPs with their functional group transformation has successfully reduced p-nitrophenol into p-aminophenol in an eco-friendly manner in the presence of light and NaBH4. Further, the synthesized AgNPs showed antibacterial potential against Gram positive and Gram negative bacteria.