Green Synthesis of AuNPs by Acinetobacter sp. GWRVA25: Optimization, Characterization, and Its Antioxidant Activity

Abstract

Bacteriogenic synthesis of metal nanoparticles is ecofriendly and greatly influenced by physico-chemical reaction parameters with respect to shape and size. Thus, present work aimed to synthesize and optimization of bacteriogenic gold nanoparticles (AuNPs) and study their antioxidant activity. <i>Acinetobacter</i> sp. cells were able to synthesize AuNPs, when challenged with tetra-chloroauric acid (HAuCl₄). By physicochemical optimization, maximum synthesis was obtained with 72 h old culture using 2.1 × 10⁹ CFU/ml cell density. Whereas, pH-7 is suitable for AuNPs synthesis. HAuCl₄ concentration (0.5 mM) enhanced the formation of monodispersed and spherical nanoparticles (15 ± 10 nm). At 37°C temperature, <i>Acinetobacter</i> sp. released nanoparticles in supernatant. From characterization, AuNPs were found to be crystalline in nature with negative surface charge. AuNPs showed up to 86% different radical scavenging ability, exhibiting antioxidant activity. In conclusion, spherical AuNPs can be synthesized using <i>Acinetobacter</i> sp. through physicochemical optimization. This is the first report of antioxidant activity exhibited by monodispersed bacteriogenic AuNPs synthesized using <i>Acinetobacter</i> sp.