Abstract: Biodegradation of Environmental Contaminants Using White Rot Fungi

Richard B. White, Steven D. Aust

White rot fungi are a common, naturally-occurring class of wood-degrading fungi that evolved to degrade lignin. Extensive research conducted since the early 1980s has shown that many of the same mechanisms used by the fungi for lignin degradation also promote the degradation of several carbon-based environmental contaminants. These contaminants include polycyclic aromatic hydrocarbons, pesticides, herbicides, wood preservatives, chlorinated solvents, PCBs, explosives, cyanide, dyes, and others.

The fungi use an extra-cellular, free-radical, nonspecific mode of degradation, which allows them to degrade both soluble and insoluble contaminants, whether they are absorbed or in solution. The extra-cellular substances secreted by the fungi include several enzymes (which catalyze the initial oxidation of contaminant molecules), hydrogen ions (to maintain a slightly acidic pH), electrons (to maintain a charge balance and to reduce contaminants through the breaking of chemical bonds), and hydrogen peroxide (a highly effective oxidizer). In addition, the fungi secrete veratryl alcohol (a free-radical mediator that catalyzes reductions) and oxalate (an organic acid that is a highly effective reductant).

Application of white rot fungi for the remediation of contaminated soils involves mixing fungal-inoculated substrates with the soil. The materials are moistened during mixing to provide an environment that is conducive to fungal growth. The soil/substrate mixture is then placed in a biocell and aerated to promote contaminant degradation. Case histories of bench-scale tests and field applications are presented.

AAPG Search and Discovery Article #90984©1994 AAPG Annual Convention, East Lansing, Michigan, September 18-20, 1994