Recent Advances Towards Improved Microbial Bioremediation of Heavy Metal Pollution

Heavy metals refer to metals with a molecular weight of 5 times more than water. Heavy metals enter the environment through mining the metal, metal casting, and smelting industries, and they return to humans through food, meat, vegetables, and contaminated drinking water. Heavy metals are removed by physical remediation, chemical remediation, and bioremediation methods, also bioremediation is cost-effective, has easy availability, and eco-friendliness. The types of mechanism microbial bioremediation of metal are biosorption, bioaccumulation, bioleaching, biomineralization, and biotransformation. Microorganisms provide resistance to heavy metals through various mechanisms, including extracellular or intracellular sequestration, extracellular barriers, reduction, and active transport (efflux). Heavy metals affect the diversity and number of microbes in the environment, which has been studied by metagenomic methods. The consortium produces stromatolites, microbial mats, and biofilms that are resistant and bioremedicated to various metals. Microorganisms also produce nanoparticles by bioremediation of metals. Nanocomposites increase the activities of microbial biostimulation, bioaccumulation, and biotransformation.