doi:10.1038/nindia.2013.97 Published online 22 July 2013
Researchers have used fungal biomass to produce silver nanoparticles that can inhibit the growth of Salmonella typhimurium, a bacterium that causes salmonellosis in humans . These nanoparticles are very promising as a therapeutic agent for supplementing drug treatment in combating salmonellosis outbreaks.
Various physical and chemical methods can be used to prepare silver nanoparticles, but they usually involve toxic chemicals, which give rise to environmental problems. In contrast, biological synthesis using plants or microorganisms is safe and cost effective. Studies have shown that fungi are more useful than plants for synthesizing metal nanoparticles.
This led the researchers to use the fungal biomass Trichoderma koningii — a non-pathogenic and agriculturally important fungus known to stifle the growth of plant pathogens — to prepare silver nanoparticles. When the fungal biomass came into contact with silver nitrate solution, silver ions were reduced to spherical silver nanoparticles with diameters between 8 and 24 nm.
A sophisticated imaging technique revealed that the silver nanoparticles are surrounded by a thin layer of material released by the fungal biomass. To assess the antibacterial properties of the nanoparticles, they were exposed to cultured S. typhimurium. Bacterial growth decreased with increasing nanoparticle concentration, whereas it increased in the absence of the silver nanoparticles.
The researchers found that using a nanoparticle concentration of 45 mg/ml inhibited bacterial growth completely.