My research focuses on harnessing the unique biodegradative abilities of the wood-rotting fungus Phanerochaete chrysosporium for a variety of applications including bioremediation of contaminated soil and water. Lignin and cellulose are structural components of wood that are responsible for its durability and suitability as a building material. One of the characteristics of wood that make it suitable for such purposes is that the Iignin component is relatively resistant to attack and decay by microorganisms. Furthermore, it is thought that lignin also protects cellulose from microbial decay. Lignin, a non-repeating heteropolymer, is the second most abundant renewable carbon compound on earth. Only cellulose is more abundant. This, combined with the fact that only a relatively few microorganisms have the ability to degrade lignin, makes its turnover the rate-limiting step in the carbon cycle. Although lignin is clearly resistant to microbial decay, certain fungi are able to degrade lignin to carbon dioxide. Many such fungi belong to the Class Basidiomycotina. Of these, P. chrysosporium has been shown to mediate extensive degradation of lignin. In addition to its ability to degrade environmentally persistent naturally occurring compounds it has been shown that P. chrysosporium is also able to mediate extensive degradation of some of the most environmentally persistent synthetic organic pollutants known. Chlorinated compounds degraded to carbon dioxide by this fungus include polychlorinated biphenyls, chlorinated dioxins, the wood preservative pentachlorophenol and the insecticides DDT and chlordane. Chlorinated anilines which are metabolites of a number of pesticides are also degraded to carbon dioxide by this fungus. Many polycyclic aromatic hydrocarbons, including benzo[a]pyrene and phenanthrene are degraded by P. chrysosporium as are the explosives 2,4,6-trinitrotoluene and RDX. A number of studies have shown that the ability of P. chrysosporium to degrade such a wide variety of organic pollutants is due, at least in part, to its lignin degrading system which is expressed when fungal cultures become limited in nutrient nitrogen and/or carbon.
