Bionanoparticles are synthesized using novel strategies through environmentally benign approaches. Emphasis is on synthesizing nanoparticles using green chemistry principles to reduce the burden of pollution on the environment. The biological approach for the synthesis of metallic nanoparticles is also described as green synthesis (bioprocess) of nanoparticles, is now being looked at as an alternative to physio-chemical approaches and generally uses biological components like plants and microbes (bacteria, fungi, algae and yeast) and cause minimal harm to the nature. The naturally occurring potential biodegradable agents like enzymes (secreted by microbes) act as reducing agents and play a very distinct role in the synthesis of nanoparticles. Most bioprocesses occur under normal air pressure and temperature, resulting in vast energy savings and reducing the use of expensive chemicals making the green approach less costly. This process of synthesis of nanoparticles using biological systems is referred to as nanobiotechnology. Nanobiotechnology has emerged as an integration between biotechnology and nanotechnology for developing biosynthetic and environmentally friendly technology for nanoparticle synthesis. This review is mainly focused on the microbial synthesis of nanoparticles utilizing the extract of bacteria and algae. In the present review, the bio-reduction capacity of various bacteria and algae is highlighted in detail, which has yet to be discussed earlier. This is a comprehensive work underlining the synthesis of nanoparticles, their bio-reduction ability, and application of nanoparticles.
