Biosynthesis of silver nanoparticles using nitrate reductase produced by Lactobacillus plantarum CAM 4: Characterization and in vitro evaluation of its antimicrobial efficiency

[Display omitted] •The nitrate reductase activity of LAB was screened using an enzymatic assay.•The nitrate reductase activity of LAB was optimized via RSM.•The biosynthesis of AgNPs by LAB was enhanced by optimized enzyme activity.•The biosynthesized AgNPs were characterized using various techniques. Among emerging nanotechnology, silver nanoparticles (AgNPs) get much attention due to their unique physicochemical properties. The present study aimed to optimize the nitrate reductase production in lactic acid bacteria (LAB) for enhanced production of AgNPs and characterize the biosynthesized AgNPs. Lactobacillus plantarum CAM 4 produced higher nitrate reductase activity (121.77 U/mL) under optimized medium containing 0.75 % of glucose, 2 % of KNO3, and pH 5.0 and successfully enhanced the AgNPs biosynthesis. Spectrophotometric analysis revealed that the biosynthesized AgNPs exhibited a peak at 430 nm. DLS analysis indicated the monodispersed characteristic of AgNPs. TEM and FE-SEM analysis shows that the AgNPs were spherical-like shape, while the EDX analysis spectrum revealed the existence of an Ag element in AgNPs. Moreover, biosynthesized AgNPs exhibited antibacterial activity against Gram-positive and Gram-negative pathogens. Results from this study provide notable insights into sustainable and inexpensive methods for the enhanced production of AgNPs using LAB.