Optimization of sporicidal activity and environmental Bacillus endospores decontamination by biogenic silver nanoparticle

The intent of this study is to decontaminate Bacillus endospores and to determine the D-values using silver nanoparticles (AgNPs) synthesized from Streptomyces sp. cell filtrate. AgNPs synthesis was performed extracellularly followed by characterization using spectrophotometer, High Resolution Transmission Electron Microscope and x-ray diffraction pattern analysis. Subsequently, the optimized conditions for the decontamination and D-value estimation of Bacillus endospores were determined using the response surface methodology. The environmental spore decontamination study was performed in mice model. AgNPs were visibly and spectroscopically identified which were spherical with the size range of less than 20 nm. The synthesized AgNPs destroyed 1log10 CFU Bacillus endospores at around 20 min. The adherence of AgNPs to the surface of spore coat, pit formation and its complete structural loss was detected under field emission scanning electron microscopy. All the mice exposed to AgNP-treated spores showed no sign of pathological lesions. The results of our study strongly suggest that the application of AgNPs as a sporicidal agent could be a new approach in consistently eliminating the hazardous Bacillus spores.