Nano microbiology, which is a rapidly evolving field of research, exists at the crossroads of biology and nanoscience. Nanotechnology is a state-of-the-art technique of using particles between 1 to 100 nm, which originated as both organic and inorganic forms. Nevertheless, the size and shape depends on the method and the materials used in the fabrication process. The particle size is important because the physicochemical stability and biological activity of the particles depend on the size.
Various physical and chemical methods are broadly used for the synthesis of nanoparticles. Though these approaches offer higher production rate and better size control over the synthesized nanoparticles, they are considered unfavorable due to high capital cost, energy requirements, anaerobic conditions, use of toxic reagents and the generation of hazardous wastes. These downsides obscure the down streaming processes, raise production cost and cause apprehensions about the environment. Moreover, the chemically synthesized nanoparticles are less biocompatible and use of toxic chemicals for synthesis and lack of stability has limited their use in clinical applications. Therefore, development of environmentally safe, economical, and biocompatible procedures for synthesis of nanoparticles are desired. Synthesis of nanoparticles by biological means offers cheap, nontoxic and eco-friendly alternatives to their counter physical and chemical methods. Microbes are found to be tiny nano-factories and microbial synthesis of nanoparticles has merged biotechnology, microbiology and nanotechnology into a new field of nano-biotechnology. Metal–microbe interactions have been widely used for bioremediation and bioleaching biomineralization, but nano-biotechnology is still at its infancy. Owing to its potent benefits it may have promising applications in nano-medicine.
For biological synthesis of nanoparticles, microbes have been exploited all over the globe. Microbes like bacteria, fungi and yeasts are mostly preferred for nanoparticle (NPs) synthesis because of their fast growth rate, easy cultivation and their ability to grow at ambient conditions of temperature, pH and pressure. Owing to their adaptability to metal toxic environments, microorganisms possess intrinsic potential to synthesize nanoparticles of inorganic materials by following reduction mechanisms via intracellular and extracellular routes. Microbes trap metal ions from the environment and turn those metal ions into the elemental form using their enzymatic activities.
Figure 1 - Microbial synthesis and applications of nanoparticles
Bacteria can remarkably reduce heavy metal ions to produce nanoparticles. Researchers have demonstrated bacteria mediated interactive pathways responsible for metal ion reduction and their ability to precipitate metals on nanoscale. A major advantage of bacteria-based nanoparticle synthesis is their large scale sustainable production with minimal use of toxic chemicals, however there are certain limitations like laborious bacterial culturing processes, less control over their size, shape and distribution. Fungi also possess various intracellular and extracellular enzymes capable of producing mono-dispersed nanoparticles. Yield of nanoparticles is high in fungi as compared to bacteria due to relatively larger biomass. Various fungal species like Verticillium luteoalbum, Colletotrichum sp., Fusarium oxysporum, Trichothecium sp., Aspergillus oryzae, Alternaria alternata, Trichoderma viride etc., have been reported to produce nanoparticles with diverse shapes and sizes, which can be used in a vast range of applications.
References
Adegbeye, M. J., Elghandour, M. M. M. Y., Barbabosa-Pliego, A., Monroy, J. C., Mellado, M., Ravi Kanth Reddy, P., & Salem, A. Z. M. (2019). Nanoparticles in Equine Nutrition: Mechanism of Action and Application as Feed Additives. Journal of Equine Veterinary Science, 78, 29–37. doi:10.1016/j.jevs.2019.04.001
Fariq, A., Khan, T., Yasmin, A. (2017). Microbial synthesis of nanoparticles and their potential applications in biomedicine. Journal of Applied Biomedicine. http://dx.doi.org/10.1016/j.jab.2017.03.004
Joye, I. J., Davidov-Pardo, G., & McClements, D. J. (2014). Nanotechnology for increased micronutrient bioavailability. Trends in Food Science & Technology, 40(2), 168–182. doi:10.1016/j.tifs.2014.08.006
Rai, H.K. and Rai, P., 2018. Solar Energy Harvesting Using Nanotechnology. International Journal of Applied Engineering Research, 13(6), pp.348-353.
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