Bioremediation [bahy-oh-ri-mee-dee-ey-shuhn] is the use of micro-organism metabolism to remove pollutants. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated elsewhere.

Some examples of bioremediation related technologies are phytoremediation (fixing environmental problems through the use of plants), bioventing (groundwater remediation), bioleaching (extracting metals from their ores through the use of living organisms), landfarming (soil remediation), bioreactors (wastewater and sewage treatment), composting, bioaugmentation (the introduction of microbial organisms to treat contaminated soil or water), rhizofiltration (filtering water through a mass of roots), and biostimulation (modification of the environment to stimulate existing bacteria capable of bioremediation).

The use of genetic engineering to create organisms specifically designed for bioremediation has great potential. The bacterium Deinococcus radiodurans (the most radioresistant organism known) has been modified to consume and digest toluene and ionic mercury from highly radioactive nuclear waste.

Bioremediation can occur on its own (natural attenuation or intrinsic bioremediation) or can be spurred on via the addition of fertilizers to increase the bioavailability within the medium (biostimulation). Recent advancements have also proven successful via the addition of matched microbe strains to the medium to enhance the resident microbe population’s ability to break down contaminants.

Microorganisms used to perform the function of bioremediation are known as ‘bioremediators.’ However, not all contaminants are easily treated by bioremediation using microorganisms. For example, heavy metals such as cadmium and lead are not readily absorbed or captured by microorganisms. The assimilation of metals such as mercury into the food chain may worsen matters. Phytoremediation is useful in these circumstances because natural plants or transgenic plants are able to bioaccumulate these toxins in their above-ground parts, which are then harvested for removal. The heavy metals in the harvested biomass may be further concentrated by incineration or even recycled for industrial use.

Mycoremediation is a form of bioremediation in which fungi are used for decontamination. The term mycoremediation refers specifically to the use of fungal mycelia (the vegetative part of a fungus) in bioremediation. One of the primary roles of fungi in the ecosystem is decomposition, which is performed by the mycelium. The mycelium secretes extracellular enzymes and acids that break down lignin and cellulose, the two main building blocks of plant fiber. These are organic compounds composed of long chains of carbon and hydrogen, structurally similar to many organic pollutants. The key to mycoremediation is determining the right fungal species to target a specific pollutant. Certain strains have been reported to successfully degrade the nerve gases VX and sarin.

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