The Problem: The character of many of the pollutants and the rate at which they can pollute results in a rapid deterioration of the environment. Inorganic pollutants include heavy metals such as cadmium, mercury, lead, zinc and the like; nonmetallic compounds like arsenic, selenium, radioactive nuclear waste, and so on. Organic contaminants include petroleum hydrocarbons, solvents, phenolic compounds, explosives, fertilizers, herbicides, pesticides etc.
The Solution: Bioremediation is an inexpensive, smart, effective in-situ or ex-situ technique used to restore the balance of polluted soil and groundwater by using naturally available plants or microbes that involves a physical or chemical process. The idea of bioremediation to overcome the adversities of these pollutants has been exploited since 600 B.C.E. But the approach of cleaning the environment using plants applied in a scientific rigorous manner has taken off over the past 30 + years.
Bioremediation encompasses a broad range of techniques within itself. Different methods to treat polluted site are phytoremediation, phytostabilization, phytosequestration, biostimulation, bioattenuation, phytoextraction, phytotransformation, phytovolaization, rhizofiltration. bioventing, bioaugmentation, biosparging, bioslurping.
A specific manifestation of bioremediation is Hyperaccumulation, which takes advantage of the ability of certain plant species to grow on metal rich soil and to accumulate extraordinarily high amounts of heavy metals in the root or shoot. Brassica, Arapidopsis, Astralagus, Hallerri are some common species used to hyperaccumulate heavy metals such as cadmium, zinc, mercury, arsenic, etc.
Recently, use of transgenic plants and genetically modified plants has been trending in this field. Understanding the molecular basis of the pathways involved in the degradation of pollutants enables improved transgenic plants for this purpose. Further analysis and discovery of genes suitable for bioremediation is essential.
Several profit and non-profit organizations have made significant contributions in an effort to remove environmental toxins using this technique as a ‘clean green technology’ across the globe. Many of the developments have been patented by the respective innovators.
The Future: Modern innovations based on synthetic microbiology show that new catabolic pathways are enabled to eliminate recalcitrant hazards from the environment. However, in doing so, prevention of gene flow into wild species and biosafety concerns must be addressed. To execute novel strategies, a different perspective is required in the field of bioremediation for which political will and funding is an absolute necessity.