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

Italo José Batista Durval,Attilio Converti,Hugo Morais Meira,Bruno Oliveira De Veras,Raquel Diniz Rufino,Leonie Asfora Sarubbo

doi:10.3390/fermentation7040233

Abstract

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 µg/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.

Highlights

IntroductionNanotechnology has been growing due to the large number of effective applications in various sectors, ranging from traditional chemical techniques to medicinal and environmental technologies [1]
The biosurfactant was successfully produced by Bacillus cereus UCP 1615 in mineral medium supplemented with residual frying oil, which makes the process more feasible, in addition to contributing to a reduction in input costs [16]
The synthesis of nanoparticles using the biosurfactant as a stabilizer was revealed, according to Tyagi et al [18], by the change in the color of the solution (Figure 1), and confirmed in Figure 2 by the presence of a maximum UV/vis absorption peak characteristic of silver nanoparticles, between 400 and 450 nm, corresponding to localized surface plasmon resonance (LSPR) [18]

Summary

Introduction

Nanotechnology has been growing due to the large number of effective applications in various sectors, ranging from traditional chemical techniques to medicinal and environmental technologies [1]. It is well accepted that a particle is nano if its diameter is from 1 to 100 nanometers (billionths of a meter), including in this range nanoparticles (NPs) considered especially practical and efficient which are traditionally synthesized by chemical means [2]. The size of silver nanoparticles (AgNPs) can be adjusted according to the desired application, as in the case of those prepared for drug delivery, which are larger than 100 nm to accommodate the amount of drug to be delivered [3].

Objectives

Methods

Results

Conclusion