Bacillus amyloliquefaciens levan and its silver nanoparticles with antimicrobial properties

In this study, the exopolysaccharide from Bacillus amyloliquefaciens PB6 was purified and identified as levan. To explore the application of this levan in nanotechnology, its silver nanoparticles (AgNPs) were prepared in a simple and green method. Transmission electron microscopy analysis revealed that the size of the synthesised AgNPs was in the range of 19.47 +/- 2.45 nm. X-ray powder diffraction analysis confirmed the face-centred cubic crystalline structure of metallic silver. Moreover, the AgNPs at the concentration of 0-12 mu g/mL exhibited a significant inhibitive effect on Staphylococcus aureus and Escherichia coli. Tested by tetrazolium-based colourimetric assay, the viability of RAW 264.7 cells was higher than 75% in the presence of 20 mu g/mL AgNPs. The results not only proved the feasibility of producing levan from B. amyloliquefaciens with high safety and a high yield, but also demonstrated the simple and cost-efficient approach of AgNPs synthesis as potential antibacterial agents from levan.