Abstract
The critical need for development of reliable and eco-friendly processes for synthesis of metallic nanoparticles has recently been realized in the field of nanotechnology. Increasing awareness toward green chemistry and biological processes has elicited a desire to explore environmentally friendly approaches for the synthesis of nanoparticles as a safer alternative to physical and chemical methods, which involves harsh conditions and use of hazardous chemicals. Therefore, the use of natural resources, including bacteria and fungi, has been exploited for cost-effective and environmentally nonhazardous nanoparticle synthesis. The rich microbial diversity of bacteria and fungi contains the innate potential for the synthesis of nanoparticles and may be regarded as potential biofactories. In fact, microbial synthesis of nanoparticles has emerged as an important branch of nano-biotechnology. The synthesis of inorganic materials by biological systems occurs through remarkable processes at ambient temperature and pressures and neutral pH. Among the various biological systems, bacteria are relatively easy to manipulate genetically, whereas fungi have an advantage of easy handling during downstream processing and large-scale production. In spite of the successes achieved in biological synthesis of nanoparticles, there is still a need to improve the rate of synthesis and monodispersity of nanoparticles. Also, microbial cultivation and downstream processing techniques must be improved, and more efficient methods should be developed. Furthermore, in order to exploit the system to its maximum potential, it is essential to understand the biochemical and molecular mechanisms involved in nanoparticle synthesis. Delineation of specific genomic pathways and characterization of gene products involved in biosynthesis of nanoparticles are required. The underlying molecular mechanisms that mediate microbial synthesis of nanoparticles will help in understanding the molecular switches and factors necessary to control the size and shape, as well as crystallinity of nanoparticles. Indeed, biological systems are still relatively unexplored, and therefore, the opportunities are open for budding nanobiotechnologists to utilize nonpathogenic biological systems for metallic nanoparticle synthesis with commercial perspectives.