Bacterial biofilm mediated bioremediation of hexavalent chromium: A review

Heavy metals in its various ionic forms present beyond the tolerable limits are considered to be toxic for human use and environment. One such primary pollutant metal is hexavalent chromium. Being more mobile and highly toxic due to its solubility in water, hexavalent chromium is potent to cause dramatically adverse effect in all aspects. Beginning from deteriorating the quality of the soil and water ecosystem, it alters the quality of the plant and plant products, and aquatic creatures primarily due to formation of reactive oxygen species (ROS). This also brings about dramatic alteration in the food web of the livings. Researchers, on exploring remedial strategies to Cr(VI), came up with several conventional and non-conventional techniques over the time along with their modernization. But the requirement of cost effective and eco-friendly strategy leads to the application of plants and microbes. After exploring a vast range of microbes, researchers stepped to explore pathogenic microbes for the noble application. Serratia marcescens, Bacillus vallismortis, Bacillus haynesii, Cupriavidus metallidurans, Bacillus cereus (Chakraborty et al. 2013), and Ochrobacterium tritici are among some of the bacterium that have been studied towards scavenging hexavalent chromium. Certain laboratory and omics studies in the past have documented the potency towards Cr(VI) scavenging by these bacteria. The review focused upon the path of hexavalent chromium from its source to bioremediation implementing this bacterial consortium, in contrast to age-old conventional and non-conventional techniques bypassing their shortcomings.