Biological synthesis of silver nanoparticles using standard fungus of Penicillium chrysogenum

Silver nanoparticles have a wide range of applications in medical sciences which their effects depend on their size. Besides, there is an ever-growing need to develop environmentally benign nanoparticles synthesis processes which created an interesting area for the researchers studying in this field. So, attempts have been made to find new microorganisms that fabricate the nanoparticles in smaller size. This study aimed to evaluate a green process for production of silver (Ag) nanoparticles synthesized using Penicillium chrysogenum (PTCC 5037 = ATCC 10003).

The standard colonies of Penicillium chrysogenum were cultured in Czapek dox broth. The supernatant of the broth was examined for the ability to produce silver nanoparticles. For that, 100mL of silver nitrate solution at a concentration of 3mM was added to 100mL of the supernatant and incubated for 24 hours at 28°C. Then, the formation of nanoparticles were confirmed by alteration of culture from yellow to brown. The synthesized silver nanoparticles were characterized by UV-visible spectroscopy, Dynamic Light Scattering (DLS), Zeta potential, Polydispersity Index (PDI), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) for particle size and shape. The synthesized nanoparticles were centrifuged at 20,000rpm by ultracentrifuge for 5 minutes to separate nano-silvers from the solution.

Addition of Penicillium citrinum supernatant to aqueous AgNO3 solution led to the appearance of brown color in solution after 24h of reaction, indicating the formation of silver nanoparticles. The UV-Vis spectrum exhibit an absorption band at around 420nm suggesting the formation of silver nanoparticles. Hence, the secreted proteins and enzymes are responsible for reduction of silver ions to convert them to silver nanoparticles. SEM and AFM photographs showed that the silver nanoparticles formed were fairly uniform in size with a spherical shape and average diameter of 40nm.

The study showed that the standard fungus of Penicillium chrysogenum has the ability of cationic silver ions to produce silver nanoparticles. Moreover, as nanoparticles formed extracellularly, they are pure and free of cellular particles which help them to be used straightly for various applications