An array of physical, chemical and biological methods have been used to synthesize
nanomaterials. In order to synthesize noble metal nanoparticles of particular shape
and size specific methodologies have been formulated. Although ultraviolet irradiation,
aerosol technologies, lithography, laser ablation, ultrasonic fields, and photochemical
reduction techniques have been used successfully to produce nanoparticles, they remain
expensive and involve the use of hazardous chemicals. Therefore, there is a growing
concern to develop environment-friendly and sustainable methods. Since the synthesis
of nanoparticles of different compositions, sizes, shapes and controlled dispersity
is an important aspect of nanotechnology new cost-effective procedures are being developed.
Microbial synthesis of nanoparticles is a green chemistry approach that interconnects
nanotechnology and microbial biotechnology. Biosynthesis of gold, silver, gold-silver
alloy, selenium, tellurium, platinum, palladium, silica, titania, zirconia, quantum
dots, magnetite and uraninite nanoparticles by bacteria, actinomycetes, fungi, yeasts
and viruses have been reported. However, despite the stability, biological nanoparticles
are not monodispersed and the rate of synthesis is slow. To overcome these problems,
several factors such as microbial cultivation methods and the extraction techniques
have to be optimized and the combinatorial approach such as photobiological methods
may be used. Cellular, biochemical and molecular mechanisms that mediate the synthesis
of biological nanoparticles should be studied in detail to increase the rate of synthesis
and improve properties of nanoparticles. Owing to the rich biodiversity of microbes,
their potential as biological materials for nanoparticle synthesis is yet to be fully
explored. In this review, we present the current status of microbial synthesis and
applications of metal nanoparticles.
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