Antimicrobial Activity of Biogenic Hop-Based Silver Nanoparticles for Application in Sugar and Alcohol Industries

Abstract

One of the largest problems in the sugar and alcohol industry is the presence of unwanted bacteria, which leads to a decrease in alcohol production. This work presents a possible way to control these undesirable bacteria using silver biogenic nanoparticles synthesized from hops. The research was aimed at synthesizing nanoparticles and evaluating their physical and chemical characteristics, antimicrobial activity and cytotoxic potential. Silver nanoparticles were synthesized using Humulus lupulus L. extract and silver nitrate solution (10-3 M). To evaluate the size and polydispersity, the dynamic light scattering (DLS) technique was used. The zeta potential and concentration of nanoparticles were assessed by microelectrophoresis and the nanoparticle tracing (NTA) technique, respectively. The analysis of the antimicrobial activity was performed by the disc diffusion test and by determining the minimum inhibitory concentration (MIC) against gram-positive bacteria. Cytotoxicity was assessed by the mitochondrial activity assay (MTT). The biogenic nanoparticles were shown to have bactericidal activity and the appropriate characteristics. Regarding the activity, the results showed that the nanoparticles obtained at pH 7 (with 5% hop flower extract) inhibited all tested bacteria at concentrations of 2.1 to 4.3 × 109 NP/mL, and the nanoparticles obtained at pH 8 (with 20% hop flower extract) inhibited the tested bacteria at concentrations of 4.8 to 6.0 × 109 NPs/mL, which means that the former presented higher potential bactericidal activity. Regarding cytotoxicity, nanoparticles of both types showed a low cell death index, and the cell viability was above 70%. Hops served as an effective stabilizing and reducing agent. The nanoparticles were effective in bacterial control and did not show cytotoxicity