Green synthesis and characterizations of silver nanoparticles with enhanced antibacterial properties by secondary metabolites of Bacillus subtilis (SDUM301120)

Abstract

Silver nanoparticles (AgNPs) have been exploited for their broad-spectrum antibacterial effects and their vast applications, which are generating interest of researchers towards green synthesis of AgNPs. In this paper, we describe a novel biosynthesis of AgNPs employing secondary metabolites of Bacillus subtilis (SDUM301120). The mean particle diameter of AgNPs was calculated by the high-resolution transmission electron microscope (HRTEM). HRTEM analysis revealed the particle was spherical and distributed in the range of 2–26 nm. Crystal nature of the nanoparticles in the face-centered cubic structure was confirmed by the peaks in the X-ray diffraction pattern corresponding to (111), (200), (220), and (311) planes. The formation of the reduced AgNPs was monitored by UV–VIS spectrophotometer analysis which displayed a peak in the region of 430–460 nm. We investigated the antibacterial activity of AgNPs against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Vibrio Parahaemolyticus ATCC 17802T, and Acinetobacter baumanni ATCC 19606T. The results show that AgNPs with enhanced antibacterial properties have significant antimicrobial effects compared with pure AgNPs, antibacterial substances (lipopeptide), and the mixture of lipopeptide and pure AgNPs. The bacteriostatic experiments compared with antibiotics showed that the obtained AgNPs had a promising future in the bacterial infections.

Keywords

• bacillus subtilis (sdum301120)
• silver nanoparticles
• antibacterial effects
• green biosynthesis
• synergistic effect