Literature Overview: Microbial Metabolism of High Molecular Weight Polycyclic Aromatic Hydrocarbons

High molecular weight polycyclic aromatic hydrocarbons (HMW PAHs) increase in hydrophobicity with increases in their molecular weight and ring angularity. Microbial strategies to deal with PAH hydrophobicity include biofilm formation, enzyme induction, and biosurfactants, the effect of which is variable on PAH metabolism depending on the surfactant type and concentration, substrate, and microbial strain(s). Aerobic HMW PAH metabolism proceeds via mineralization, partial degradation, and cometabolic transformations. Generally, bacteria and nonlignolytic fungi metabolize PAHs via initial PAH ring oxidation by dioxygenases to form cis-dihydrodiols, which are transformed to catechol compounds by dehydrogenases and other mono-and dioxygenases to substituted catechol and noncatechol compounds, all ortho-or metacleaved and further oxidized to simpler compounds. However, lignolytic fungi form quinones and acids to CO2. This review discusses the pathways for HMW PAH microbial metabolism. (C) 2008 Wiley Periodicals, Inc.