Synthesis of nano silver particle using lactic acid bacteria culture filtrate and determination of antimicrobial effects on methylcellulose films

This study was conducted to investigate whether silver nanoparticles synthesized by biological methods using lactic acid bacteria culture filtrate can be used as antimicrobial agents in methyl cellulose films. Silver nanoparticles were synthesized using the supernatants of five different lactic acid bacteria cultures under alkaline conditions (pH: 12) and a final AgNO3 concentration of 10 mM. Silver nanoparticle biosynthesis occurred rapidly within a few minutes. Visual observation, UV-Vis Spectrophotometer, FTIR, XRD and SEM methods were used for the characterization of AgNPs. Biosynthesized silver nanoparticles were confirmed by the color changes that occurred after synthesis. The UV-visible spectrum showed a peak at 402.44 nm, corresponding to the plasmon absorbance of silver nanoparticles. Five peaks corresponding to the (111), (200), (220), (311) and (222) planes detected in the X-ray diffraction (XRD) graphs of all synthesized AgNP samples were best matched with Face Centered Cubic (FCC) silver crystals. The average size of the obtained AgNPs was calculated as 9.74 nm-11.12 nm using Scherrer's formula. The average diameter of silver nanoparticles was found as 13.55nm-26.45 nm in SEM micrographs. FTIR spectrum showed the presence of high levels of AgNP stabilizer proteins and other downstream metabolites that play a role in the reduction of Ag+ to Ag0 nanoparticles. Then, the antimicrobial effects of the characterized AgNPs on E. coli; S. aureus, L. monocytogenes, P. chrysogenum and S. cerevisiae were evaluated. All of the silver nanoparticle solutions obtained from the lactic acid bacteria culture filtrate showed antimicrobial activity against the bacteria, yeasts and molds used in study. Silver nanoparticle powders obtained from the solutions showed antimicrobial activity against E. coli; S. aureus and L. monocytogenes, but did not show antimicrobial activity against P. chrysogenum and S. cerevisiae. Edible methyl cellulose films containing certain amounts of silver nanoparticles were produced and it was observed that E. coli, S. aureus, L. monocytogenes, P. chrysogenum and S. cerevisiae bacteria did not grow on some of the films depending on the dose used. This study showed that antimicrobial films produced using the combination of methyl cellulose polymer and AgNP obtained from culture filtrate of lactic acid bacteria have the potential to be used in antimicrobial packaging systems. However, further research is needed for their use on foods.