Green synthesis of functional metallic nanoparticles by dissimilatory metal-reducing bacteria “Shewanella”: A comprehensive review

The biosynthesis strategy of nanoparticles has attracted much attention due to the mild synthesis conditions, environmental-friendly properties, and low costs. Biosynthesized nanoparticles (bio-NPs) not only show excellent physicochemical properties, but also exhibit high stability, enlarged specific surface area, and excellent biocompatibility, which are crucial for industrial, agricultural, and medical fields. Shewanella, a kind of dissimilatory metal-reducing bacteria, is regarded as a typical biosynthesis-functional bacteria class with wide distribution and strong adaptability. Thus, in this paper, functional bio-NPs by Shewanella were reviewed to provide a comprehensive view of current research progress. The biosynthetic mechanisms of Shewanella are summarized as the Mtr pathway (predominant), extracellular polymeric substance-induced pathway, and enzyme/protein-induced pathway. During the biosynthesis process, biological factors along with the physicochemical parameters highly influenced the properties of the resultant bio-NPs. Till now, bio-NPs have been applied in various fields including environmental remediation, antibacterial applications, and microbial fuel cells. However, some challenging issues of bio-NPs by Shewanella remain unsolved, such as optimizing suitable bacterial strains, intelligently controlling bio-NPs, clarifying biosynthesis mechanisms, and expanding bio-NPs applications.