Biologically synthesized silver nanoparticles against pathogenic bacteria: Synthesis, calcination and characterization

In this study, the silver nanoparticles (AgNPs) were synthesized using a strain Bacillus subtilis KMS2-2 by extracellularly. The effect of calcination (200 degrees C for 30 min) on structural characteristics and antibacterial activity of the AgNPs were investigated. The inhibitory effect of AgNPs against pathogenic bacteria such as Pseudomonas fluorescens MTCC 1749, Proteus mirabilis MTCC 425, Escherichia coli MTCC 1610, Bacillus cereus and Staphylococcus aureus MTCC 2940 was tested by agar-well diffusion method. The synthesized AgNPs before and after calcination were spherical crystalline in nature and had size range from 18-100 nm and 49-153 nm, respectively and were determined by scanning electron microscope (SEM) and X-ray diffraction analysis (XRD). Further, Fourier transform Infrared spectroscopic (FT-IR) analysis revealed the presence of bioactive compounds in the crude AgNPs as capping materials. The in vitro antibacterial studies revealed that crude AgNPS strongly inhibited the growth of tested pathogenic bacteria, whereas, the calcined AgNPs didn't show growth inhibition activity.