This article was researched and written by a student at the University of Vermont participating in the Encyclopedia of Earth's (EoE) Student Science Communication Project. The project encourages students in undergraduate and graduate programs to write about timely scientific issues under close faculty guidance. All articles have been reviewed by internal EoE editors, and by independent experts on each topic.

Introduction

Mycoremediation is the process of degrading or removing toxicants from the environment using fungi. Fungi are important decomposers in the natural environment. They create enzymes to degrade the plant polymers cellulose and lignin, two very durable compounds that give plants their structure. Using similar mechanisms, fungi can also break down certain toxic substances.  Mycoremediation is a form of bioremediation, which more broadly refers to reducing toxicants in the environment using biological processes.  Adjustments to local soil and water conditions can help to encourage biological activity and the subsequent degradation or removal of toxic substances, though mycoremediation. White rot fungi, for example, will break down more complex or harmful compounds if they are provided with a carbon-rich medium such as straw.

The term ‘mycoremediation’ was coined by the American mycologist Paul Stamets, who has studied many potential uses of mushrooms for over 30 years, including their culinary, medicinal, and restorative properties. Along with mycoremediation, he has also explored the concepts of mycofiltration, mycoforestry, mycopesticides, and mycorestoration.

Process

Fungi can be used to degrade organic compounds such as petroleum products and pesticides in soil. Like lignin, these compounds are based on hydrocarbons (chains of carbon and hydrogen). Enzymes from the fungal mycelia are able to cleave certain atoms like chloride (Cl) off of larger molecules, and then break the bond between hydrogen and carbon. As a result, mycoremediation may break down certain chemicals such as chlorinated pesticides which tend to persist in the environment. Bacteria can help to further degrade these compounds into final products including carbon dioxide (CO₂), water, and potentially methane (CH₄).

Fungi have also proven useful in remediation of heavy metals, such as lead (Pb) and cadmium (Cd). These metals are already at their simplest state and are not degraded further; fungi can extract them from soil or water and accumulate them in their tissues. Mushrooms used for such purposes would likely need to be treated as hazardous waste after this practice, depending on local conditions. 

Examples of Mycoremediation

Mycoremediation has been applied to contaminated soil, oil spills, industrial chemicals, contaminated surface water, and farm waste. Some specific examples include:
• Lentinus edodes (shiitake mushroom) can degrade pentachlorophenol (PCP), a broad-spectrum biocide that is more toxic than DDT.
• Pleurotus pulmonarius (lung or Italian oyster mushroom) can degrade atrazine, a herbicide that is contaminating groundwater in many midwestern US states.
• Phanerochaete chrysosporium, a white rot fungus, can degrade compounds such as biphenyl and triphenylmethane.
Mycoremediation is not widely used at present, but the above applications suggest its broader potential. Fungi perform a wide variety of ecosystem functions and may be a clean, simple and relatively inexpensive method of environmental remediation, especially if species native to each site are used.

References

Singh, Harbhajan. 2006. Mycoremediation: Fungal Bioremediation. Hoboken, NJ: Wiley-Interscience.
Stamets, Paul. 2005. Mycelium Running. Berkeley, CA: Ten Speed Press.

Further reading

• Battelle Mycoremediation Technologies [1]
• Fungi Perfecti - Paul Stamets [2]
• "Mycoremedia What?" [3] Bohemian.com
• Mycoremediation of aged petroleum hydrocarbon contaminants in soil [4]
• Mycoremediation for removal of fecal coliform bacteria and nutrients in the Dungeness watershed, Washington [5]