Mycoremediation

Mycoremediation, a form of bioremediation, is the process of using fungi to degrade or sequester contaminants in the environment. Stimulating microbial and enzyme activity, mycelium reduces toxins in-situ. Some fungi are hyperaccumulators, capable of absorbing and concentrating heavy metals in the mushroom fruit bodies.

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.[1] 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.[2]

There are many factors that affect the rate and ability for mushrooms to break down toxins, the first of which is the physical nature of the hydrocarbons. Generally, contaminants that are molecularly simpler are easier to break down than more complicated ones. Temperature also controls the rate at which contaminants are broken down. Low temperatures slow the process and warm temperatures speed it up. Fungi prefer a pH of 4 to 5, that is they prefer a pH which is slightly more acid than a neutral pH which is 7. Oxygen is also essential to fungal metabolism. The initial step of hydrocarbon degrading involves adding oxygen to the hydrocarbon, and so a lack of oxygen in the environment slows the process.[3]

Oyster mushrooms (Pleurotus ostreatus)

In an experiment conducted in conjunction with Dr. S. A. Thomas, a major contributor in the bioremediation industry, a plot of soil contaminated with diesel was inoculated with mycelia of oyster mushrooms; traditional bioremediation techniques (bacteria) were used on control plots. After four weeks, more than 95% of many of the PAH (polycyclic aromatic hydrocarbons) had been reduced to non-toxic components in the mycelial-inoculated plots. It appears that the natural microbial community participates with the fungi to break down contaminants, eventually into carbon dioxide and water. Wood-decay fungi are particularly effective in breaking down aromatic pollutants (toxic components of petroleum), as well as chlorinated compounds (certain persistent pesticides).

In 2007 a similar method was used in San Francisco. Oil had contaminated the shoreline after a cargo ship spilled 58,000 gallons of heavy fuel oil. Hair mats, the size of a doormat, acted as sponges to soak up spilled oil. An experiment was designed that collected and layered with oyster mushrooms and straw: the mushrooms broke down the oil and after several weeks the resulting soil was clean enough to be used for roadside landscaping.[4][5]

Mycofiltration is a similar process, using fungal mycelia to filter toxic waste and microorganisms from water in soil.

See also

References

  1. ↑ Stamets, Paul. undated. "Helping the Ecosystem through Mushroom Cultivation Archived September 25, 2005, at the Wayback Machine.." Adapted from Stamets, P. 1998. "Earth's Natural Internet." Whole Earth Magazine, Fall 1999.
  2. ↑ Stamets, Paul (2004). "Magic Mushrooms: Planetary Healing with Deep Biology". In Kenny Ausubel & J.P. Harpignies. Nature's Operating Instructions: The True Biotechnologies. San Francisco: Sierra Club Books. p. 39. ISBN 1578050995.
  3. ↑ Singh, Harbhajan (2006). Mycoremediation: fungal bioremediation. New York: Wiley-Interscience. ISBN 0-471-75501-X.
  4. ↑ "Mycoremediation (Bioremediation with Fungi) – Growing Mushrooms to Clean the Earth. A mini-review".
  5. ↑ May, Meredith (14 November 2007). "Hair and mushrooms create a recipe for cleaning up oily beaches". San Francisco Chronicle. Retrieved 8 May 2013.

External links

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