Green synthesis of silver nanoparticles and its antibacterial activity using fungus Talaromyces purpureogenus isolated from Taxus baccata Linn.

The present study is focused on the synthesis of silver nanoparticles (AgNPs) utilizing endophytic fungus Talaromyces purpureogenus, isolated from Taxus baccata Linn. Extracellular extract of Talaromyces purpureogenus has shown occurrence of secondary metabolites viz. terpenoids and phenols. Gas chromatography-mass spectroscopy analysis showed the presence of 16 compounds. Techniques like Ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering, field emission gun scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction were employed to characterize the synthesized AgNPs. UV–Vis spectroscopy showed sharp peaks at 380–470 nm which indicates the presence of metallic silver. FTIR analysis showed the presence of various functional groups like phenols, hydroxyl groups, and primary amines. In DLS, Z-average size and PdI of synthesized AgNPs were 240.2 r.nm and 0.720 respectively, with zeta potential − 19.6 mV. In FEG-SEM and HRTEM the spherical AgNPs showed diameter in the range of 30–60 nm. In EDS analysis the weight percent of Ag is 67.26% and atomic percent is 43.13%. From XRD analysis the size of AgNPs was found to be 49.3 nm with face-centered cubic crystalline nature of fungal synthesized AgNPs. These nanoparticles have shown significant antibacterial activity against tested strains viz. Listeria monocytogenes (13 ± 0.29 mm), Escherichia coli (17 ± 0.14 mm), Shigella dysenteriae (18 ± 0.21 mm) and Salmonella typhi (14 ± 0.13 mm). These synthesized AgNPs have shown effective free radical scavenging activity against 2,2′-diphenyl-1-picrylhydrazyl. The present study showed that the endophytic fungus Talaromyces purpureogenus can be used as a prominent source to synthesize AgNPs by using biological, ecofriendly, and in a non-toxic way accompanied by antibacterial and antioxidant properties which further can reduce the harvesting pressure faced by Taxus baccata.

Graphical Abstract