Green synthesis of silver nanoparticles using endophytic bacterium Bacillus zanthoxyli GBE11 and their antimicrobial activity

Recently, the biosynthesis of silver nanoparticles (AgNPs) by microbes to develop biocompatible nanomaterials for use in environmental protection and biomedicine has become popular. The fabrication of AgNPs for application in monotherapy or combination therapy will open avenues to produce new antibacterial drugs. The synthesis of AgNPs by endophytic bacteria is a less explored field. In the present study, an eco-friendly and economical method was developed for the formation of AgNPs by using the endophytic bacterium Bacillus zanthoxyli GBE11, isolated from the leaves of Ginkgo biloba, to estimate their antibacterial potential. The change of the mixture from colorless to dark brown verifies the initial formation of AgNPs. Endophytic B. zanthoxyli-produced AgNPs (Bz-AgNPs) were characterized using UV-vis spectrometry and surface plasmon resonance at 439 nm. X-ray diffraction analysis yielded diffraction intensities with 2 theta angles of 27.66 degrees, 32.06 degrees, 38.10 degrees, 46.11 degrees, and 77.13 degrees, confirming the crystalline nature of nanoparticles. Especially, the Fourier transform infrared spectra revealed the existence of probable bioreduction molecules required for the synthesis of Bz-AgNPs. Transmission electron microscopy indicated the polydispersity of the Bz-AgNPs with a size of 3.68-31.60 nm. Our results indicated that the Bz-AgNPs had a strong antibacterial effect against Staphylococcus aureus ATCC6538P, Salmonella typhi enterica ATCC25922, Escherichia coli DH5 alpha, Bacillus subtilis WB800, and Pseudomonas aeruginosa ATCC27853. The data showed that Bz-AgNPs are prospective antimicrobial agents that are available for the manufacture of new drugs to overcome multidrug resistance.