Bio-removal of Heavy Metals using Iron-oxidizing Bacteria: A Novel Approach in Environmental Biotechnology

The pharmaceutical and hygienic productivity of wastewater containing pollutants, especially heavy metals such as nickel, mercury are brought into the nature. Recently, bio-removal of heavy metals has attracted significant attention as an eco-friendly approach for the research departments of the pharmaceutical companies. In the current study, removal of heavy metals including mercury and nickel was assessed using isolated iron-oxidizing bacteria from different sources. To this end, bacterial populations were isolated from a variety of aquatic ecosystems; including Mahallat Pond, mountainous rivers, iron industry wastewater, and treated industrial wastewater. The bacteria were cultured and purified in iron-oxidizing media after which the removal of mercury and nickel was measured through culturing the isolated bacteria in 3 different media of Luria-Bertani, PHGII, and iron-oxidizing media containing the heavy metals (2 ppm). The results proved LB as a suitable medium for all the isolated bacteria in removing the heavy metals. It was shown that approximately 100% of the mercury was removed through the bacterial cultured in LB medium. The removal of nickel also reached its maximum of 30% by bacterial culture in LB medium. Then, the phylogenetic study according to 16S rRNA gene sequences showed that the isolated bacteria from iron industry wastewater was Bacillus velezensis CR-502(T). In summary, this study demonstrated the impressive ability of these bacteria for mercury removal and the effects of different media on the removal of mercury and nickel.