Green Synthesis of Silver Nanoparticles Using a Biosurfactant from Bacillus cereus UCP 1615 as Stabilizing Agent and Its Application as an Antifungal Agent

Silver nanoparticles have great potential in a wide range of applications. Therefore, the purpose of this work was to synthesize, in a simple and green way, via the Tollens method, silver nanoparticles (AgNPs), using as a stabilizer the biosurfactant produced by Bacillus cereus UCP 1615 cultivated in a low-cost medium, with waste frying oil as a substrate. The obtained nanoparticles were identified and morphologically characterized using ultraviolet/visible (UV/vis) spectroscopy, scanning electron microscopy (SEM), and zeta potential. The maximum UV/vis absorption was observed at 400 nm for newly formed silver nanoparticles, while, for silver nanoparticles stored for 120 days, the peak was observed at 430 nm. SEM micrographs confirmed the formation of nanoparticles, with predominantly spherical structures. The average size of the formed nanoparticles was estimated to be 20 nm. The presence of the biosurfactant promoted stability, as a zeta potential of -23.4 mV was observed. The antimicrobial potential of AgNPs was evaluated at different concentrations against three pathogenic fungi (Aspergillus niger, Penicillium fellutanum, and Cladosporium cladosporioides). No less than 100% and 85% inhibitions of P. fellutanum and A. niger growth were observed, respectively, at the AgNP concentration of 16.50 mu g/mL in potato dextrose agar medium. These results suggest the potential use of the biosurfactant as a stabilizer for silver nanoparticles and its application as an antimicrobial agent.