Bioremediation of Metals
Using Living Organisms To Bioremediate Metals
This week we are going to discuss an innovative and eco-friendly method of cleaning up contaminated environments through a process known as bioremediation. It involves removing or neutralizing heavy metals from soil, water, or other polluted environments by employing living organisms, including bacteria, fungi, and plants. This approach is becoming increasingly popular since it is more affordable and sustainable than conventional cleanup approaches.
Metals, such as arsenic, lead, cadmium, chromium, and mercury, are persistent pollutants that, in high quantities, pose serious dangers to ecosystems and public health. These metals may enter the environment due to agriculture, industrial processes, inappropriate waste management, landfills, mining operations, or unintentional spills.
Some bacteria and plants have a natural capacity to tolerate and digest metals, which is used in bioremediation. Thanks to special genetic and biochemical pathways, these species can bind, sequester, convert, or destroy metal pollutants. Phytoextraction and bioleaching are the two basic methods used in metal bioremediation.
Phytoextraction is the process of removing and storing metals from the soil using plants. Certain plant species, referred to as hyperaccumulators, have the capacity to absorb and store substantial amounts of metals in their tissues. These plants can be grown on contaminated land, after they have completed their life cycle and are harvested and removed from the area, they effectively take the metals with them.
The solubilization of metals from solid matrices is dependent on microbial activity. This includes ores or polluted soil. Enzymes from specific bacteria and fungi can oxidize or decrease metal complexes, making them more soluble and removing them easier. When these microbes are introduced into a contaminated environment, they help release metals under regulated circumstances so they can be recovered and processed further or securely disposed of. “After the plants have been allowed to grow for several weeks or months, they are harvested and either incinerated or composted to recycle the metals. This procedure may be repeated as necessary to bring soil contaminant levels down to allowable limits.” (EPA, 1999)
Metals bioremediation has a number of benefits over conventional remediation techniques. First, it uses the innate capacities of living things in a natural and sustainable way. This lessens the need for harsh chemicals and energy-intensive processes, positively impacting the environment. Additionally, bioremediation can be carried out in situ or at the contaminated site, eliminating the need for excavation and transporting vast amounts of polluted material.
The adherence of heavy metals to the cell surface in a metabolism independent fashion is the initial step, followed by the internalization of metal ions via the cell membrane in the second step [16]. This resembles the cellular uptake of essential ions like Na2+, K+, and Ca2+. The metal cations with equal charge and ionic radius hijack the essential ion channels and enters the intracellular phase [16]. Active transporters are evidenced for cadmium, chromium, silver, lead, mercury, strontium, uranium, thorium in Pseudomonas putida, Bacillus subtilis, Thiobacillus ferrooxidans, Rhizopus arrhizus, Micrococcus luteus, Saccharomyces cerevisiae, and Aspergillus niger, respectively [20]. The intracellular reduction of heavy metals follows a variety of metabolic pathways. (Jeyakumar et al, 2022)
Additionally, bioremediation has the potential to be more economical than other methods, particularly for lengthy or large-scale cleanup initiatives. Utilizing naturally occurring organisms allows cleanup in locations with limited financial resources since it eliminates the need for costly infrastructure and equipment.
However, there are some restrictions and difficulties related to metal bioremediation. The kind and concentration of the metal pollutants, the particular microbes or plants utilized, the ambient conditions, and the availability of nutrients are some of the variables that affect how effective the process is. A considerable reduction in metal concentrations can also take a while to achieve due to the process' potential for slowness.
Overall, bioremediation of metals is a developing and promising topic that provides a long-lasting and affordable method for cleaning contaminated areas. We are always learning more about the potential uses and enhancing the effectiveness of this ecologically friendly strategy thanks to ongoing research and technology development. In the upcoming posts we will look at the different approaches using algae, bacteria, fungi, and plants.
Resources:
EPA.gov. Pyhtoremediation Resourse Guide. EPA 542-B-99-003. June, 1999. 56pp. www.epa.gov/tiohttps://www.epa.gov/sites/default/files/2015-04/documents/phytoresgude.pdf
Jeyakumar, Parasakthi, Chandrani Debnath, R Vijayaraghavan, Muthusivaramapandian Muthura, J Trends in Bioremediation of Heavy Metal Contaminations. Environmental Engineering Research. 2023;28(4): 220631:220631-0. Publication Date (Web): 2022 October 16. doi:https://doi.org/10.4491/eer.2021.631