Abstract
Biological method for silver nanoparticles synthesis has been developed to obtain cost effective, clean, nontoxic, and ecofriendly size-controlled nanoparticles. The objective of this study is extracellular biosynthesis of antimicrobial AgNPs using cell-free supernatant of a localStreptomycessp. strain SSHH-1E. Different medium composition and fermentation conditions were screened for maximal AgNPs biosynthesis using Plackett-Burman experimental design and the variables with statistically significant effects were selected to study their combined effects and to find out the optimum values using a Box-Behnken design. The synthesized AgNPs were characterized using UV-visible spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive X-ray spectroscopy. Rapid biosynthesis of AgNPs was achieved by addition of 1 mM AgNO3solution to the cell-free supernatant. The produced particles showed a single surface plasmon resonance peak at 400 nm by UV-Vis spectroscopy which confirmed the presence of AgNPs.Streptomycessp. SSHH-1E was identified asStreptomyces narbonensisSSHH-1E. Transmission electron microscopy study indicated that the shape of AgNPs is spherical and the size is ranging from 20 to 40 nm. Fourier transform infrared spectroscopy analysis provides evidence for proteins as possible reducing and capping agents. Furthermore, the biosynthesized AgNPs significantly inhibited the growth of medically important pathogenic Gram-positive and Gram-negative bacteria and yeast. The maximum biosynthesis of AgNPs was achieved at initial pH of 8, peptone of 0.5 g, and inoculum age of 48 h. The statistical optimization resulted in a 4.5-fold increase in the production of AgNPs byStreptomyces narbonensisSSHH-1E.
Highlights
Nanotechnology involves the production, manipulation, and use of materials ranging in size from less than a micron to that of individual atoms
The results showed that inoculum age, pH, and peptone were found as the most important significant factors influencing the AgNPs biosynthesis
It can be concluded that Streptomyces narbonensis SSHH1E is an excellent microbial resource for the synthesis of AgNPs
Summary
Nanotechnology involves the production, manipulation, and use of materials ranging in size from less than a micron to that of individual atoms. An important aspect of nanotechnology is the development of toxicity-free synthesis of metal nanoparticles which is a great challenge. In its metallic as well as ionic forms, exhibits cytotoxicity against several microorganisms and can be used as an antimicrobial agent [1]. Silver nanoparticles (AgNPs) have been widely employed in various fields due to their physicochemical properties including extremely small size and large surface area relative to their volume [2]. AgNPs can be used in medicine to reduce infections as well as to prevent bacteria colonization on prostheses [4], as antimicrobial agents in surgically implanted catheters in order to reduce the infections caused during surgery [5], vascular grafts [6], dental materials [7], and stainless steel materials and human skin [8]. In the last few decades there has been increased interest in reducing
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