Biodegradation

Article By:

Focht, Dennis D. Department of Soil and Environmental Sciences, University of California, Riverside, California.

Last reviewed:May 2020

DOI:https://doi.org/10.1036/1097-8542.422025

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• Biodegradation, published June 2014:Download PDF Get Adobe Acrobat Reader

The destruction of organic compounds by microorganisms. Biodegradation is a process (carried out by microorganisms) that decomposes organic material into its constituent elements or new compounds. Microorganisms, particularly bacteria (and fungi to a lesser extent), are responsible for the decomposition of both natural and synthetic organic compounds in nature (see illustration). Mineralization results in complete conversion of a compound to its inorganic mineral constituents [for example, carbon dioxide (CO₂) from carbon; sulfate or sulfide from organic sulfur; nitrate or ammonium from organic nitrogen; phosphate from organophosphates; or chloride from organochlorine]. Because carbon comprises the greatest mass of organic compounds, mineralization can be considered in terms of CO₂ evolution. Radioactive carbon-14 (¹⁴C) isotopes enable scientists to distinguish between mineralization arising from contaminants and soil organic matter. However, mineralization of any compound is never 100% because some of it (10–40% of the total amount degraded) is incorporated into the cell mass or products that become part of the amorphous soil organic matter, commonly referred to as humus. Thus, biodegradation comprises mineralization and conversion to innocuous products—namely, biomass and humus. Primary biodegradation is more limited in scope and refers to the disappearance of the compound as a result of its biotransformation to another product. See also: Bacteria; Bacteriology; Carbon; Carbon dioxide; Fungi; Humus; Microbial ecology; Microbiology; Soil; Soil ecology; Soil microbiology

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