Effect of polylactic acid-silver nanoparticle nanocomposite on the kinetics of Escherichia coli growth

Effect of polylactic acid-silver nanoparticle nanocomposite on the kinetics of Escherichia coli growth

Samira Molapour Rashedi¹, Mersedeh Fatemeh Yazdan Bakhsh², Fahimeh Karimi³, Mehras Yazdan Bakhsh⁴

_{1-PhD student in Textile Chemical Engineering, Islamic Azad University, Science and Research Branch, Tehran, Iran}

_{2- Professor at the University of Applied Sciences - Jihad University Karaj - Iran and CEO at the Company of Dara Cellulose Nita Karaj-Iran}

_{3- Doctor of Chemical and Physical Engineering, Islamic Azad University, Tehran Branch and Labor Inspector, Karaj-Iran}

_{4- Master of Mining Engineering, Islamic Azad University of Tehran, South Iran and Director (R&D) at the Company of Dara Cellulose Nita Karaj-Iran}

_{rashedisamira@yahoo.com, yazdanbakhsh1800@gmail.com, fahimehkarimi1388@gmail.com, mehras.yazdanbakhsh@gmail.com}

ABSTRACT:

Nowadays the application of biodegradable materials in food packaging has gained increasing attention due to their high potentials. These materials exhibit lower resistance against gases and water permeation and are mechanically weaker. One of the approaches to resolve these problems in their composition with other useful substances. In this study, polylactic acid/silver nanocomposites (0.5 and 2 wt.% nanosilver) were prepared by the solvent casting method. The antimicrobial effect of these films on the growth parameters of Escherichia coli (a Gram-negative bacterium)  was investigated by a Solvent casting test using Gompertz and Logistic models which indicated a 4.3% increase in the lag phase duration and a 30.9% decline in the E. coli growth rate as well as 32.6% reduction in the final population of this bacterium. It was also observed that an increment in the silver nanoparticle percentage can enhance the antimicrobial activity of this nanocomposite. A new peak was observed in the FTIR spectrum of the silver nanoparticle-containing nanocomposite at 3620 cm^-1 for all nanoparticle contents (0.5 and 2 wt.%) which can be assigned to the chemical interactions between silver nanoparticles and polylactic acid. XRD patterns also indicated the peaks related to Ag(111), Ag(200), Ag (220), and Ag (311) representing the presence of crystalline silver nanoparticles.

Keywords: Escherichia coli, polylactic acid, antimicrobial activity, silver nanoparticles, nanocomposite