Among metallic nanoparticles, silver nanoparticles (AgNPs) have numerous applications in the field of nanobiotechnology due to their unique antimicrobial efficiency as growth inhibitors, killing agents or antibiotic carriers (Hamidi et al., 2019). AgNPs have widely attracted attention for the food, cosmetics and biomedical applications (Sondi and Salopek-Sondi, 2004). In the last few years, different chemical and physical methods had been included in AgNPs synthesis. These incorporated methods produced contaminated, toxic AgNPs in low yields. So, scientific researchers went to the biological synthesis of AgNPs using microorganisms (Wang et al., 2019). Through microbial biosynthesis, numerous scientists used bacterial strains in AgNPs biosynthesis due to their rapid growth rate and highly efficient enzymatic system (Galvez et al., 2019). The use of bacterial crude metabolites was embedded as reducing agents of silver ions into safe and ecofriendly AgNPs that called extracellular biosynthesis (De Souza et al., 2019). The extracellular production is more prioritized than the intracellular which requires extraction and purification of AgNPs from the microbial growth. In addition, the extracellular production was confirmed to include high amounts of proteins which acted as capping agents (Annamalai and Nallamuthu, 2016). One of the mechanistic aspects for AgNPs biosynthesis is the secreted enzymes by bacteria that act as reducing agents for silver ions (Quinteros et al., 2016). The shape and size of the biosynthesized nanoparticles (NPs) could be handled throughout controlling the production parameters such as concentration of metal ions, temperature, incubation period, pH and effect of solar irradiation (Sumitha et al., 2019). AgNPs have a strong bactericidal effect against a broad spectrum of bacteria such as Pseudomonas sp., Acinetobacter sp., Escherichia sp., Vibrio sp. and Salmonella sp. (Paul and Londhe, 2019). Furthermore, the biosynthesized AgNPs showed significance antifungal potential against Aspergillus flavus, A. nomius and A. parasiticus, Alternaria alternata, Fusarium sp., Candida tropicalis and C. albicans was reported (Bocate et al., 2019). This makes the AgNPs a potential candidate as a new generation of antifungal agents. The present work aimed to obtain a potent bioreductant bacterium possessing the ability to synthesize AgNPs extracellularly with efficient antimicrobial activity.
