Mechanisms of Degradation by White Rot Fungi

Abstract

White rot fungi use a variety of mechanisms to accomplish the complete degradation of lignin and a wide variety of environmental pollutants. Both oxidative and reductive reactions are required for the metabolism of both lignin and environmental pollutants. The fungi secrete a family of peroxidases to catalyze both direct and indirect oxidation of chemicals. The peroxidases can also catalyze reductions using electron donors to generate reductive radicals. A cell-surface membrane potential can also be used to reduce chemicals such as TNT. -Environ Health Perspect 103(Suppl 5):59-61 (1995)

Bioelectrochemical and Conventional Bioremediation of Environmental Pollutants

“…Enzymes used in the degradation of lignin are lignin peroxidase (LiP), manganesedependent peroxidase (MnP), manganese-independent peroxidase (MIP) and laccase [11]. Lignin peroxidases are distinct in that they have higher oxidation potentials than most peroxidases [52]. Over the course of thirty days, P. chrysosporium lacking nitrogen converted 50% of DDT with approximately 10% mineralized and the remainder as oxidized metabolites [51].…”

Explorations and Applications of Enzyme-linked Bioremediation of Synthetic Dyes

“…Generally, peroxidases are ubiquitous in nature; found in fungi, plants, animals, and eubacteria; and are classified within different superfamilies on the basis of their sequence homologies; animal and nonanimal peroxidases (former plant peroxidases) form the largest groups. The plant superfamily is further grouped into three subclasses according to cellular localization: class I-intracellular, organelle-associated, and bacterial peroxidases (e.g., cytochrome c peroxidase [CCP]); class II-secretory fungal peroxidases, including ligninolytic peroxidases such as LiPs, MnPs, and VPs [41][42][43]; and class III-secreted plant peroxidases (horseradish peroxidase [HRP]) [37]. Among peroxidases, a new superfamily-"dye-decolorizing peroxidases"-has arisen.…”

“…Initially, the native enzyme, which is in the ferric form Fe III , undergoes two-electron oxidation by H 2 O 2 to produce compound I (oxyferryl porphyrinyl radical [Fe IV =O ⋅+ ]). One electron is removed from the ferric iron Fe III to form the ferryl Fe IV , whereas the second electron is withdrawn from the porphyrin ring to form a porphyrin cation radical [43]. During this reaction step, H 2 O 2 is reduced to water.…”

Biodegradation and Bioremediation of Organic Pesticides

“…Peroxidases participate in cell response to oxidative damage and most of them are metalloproteins. They are extemely sensitive to the presence of azide, and inhibitor of metalloenzymes, with the exception of lignine peroxidases from fungi (25). It is known that ligninolytic fungi secrete peroxidases and oxidases to degrade lignine (25,26).…”

“…Unfortunately, the nutritional, humidity and pH requirements for some species of fungi and algae represent a big obstacle for its use. Fungi secrete peroxidases, dioxygenases and oxidases able to biodegrade pesticides more efficiently than cytochrome P450 (25). Lignine peroxidase, laccase, and dichlorohydroquinone dioxygenase are some examples of biotransformation enzymes produced by fungi like Phanerochaete chrysosporium, Pleurotus ostreatus, Ganoderma australe and Fusarium ventricosum; the three former are ligninolytic, and the latter is a saprobe.…”