Diversity, biodegradation and bioremediation of polycyclic aromatic hydrocarbons

Abstract

Polycyclic aromatic hydrocarbons (PAHs) consist of a class of chemicals with two or more fused benzene rings in linear, angular or cluster arrangements. Among the most abundant environmental pollutants, the aromatic compounds are of major concern because of their persistence and toxicity. PAHs are ubiquitous in nature found throughout the environment in air, water and soil. They are produced during fossil fuel combustion, waste incineration, or as byproducts of industrial processes, such as coal gasification and petroleum refining, and often released in large quantities into the environment (Finlayson-Pitts and Pitts 1997). There are more than 100 different PAHs which occur as complex mixtures, not as single compound. One of the main reasons for the prolonged persistence of hydrophobic hydrocarbons in the environments is their low water solubility which increases their sorption to soil particles and limits their availability to biodegrading microorganisms (Cerniglia 1993). The decontamination of PAHpolluted sites is mandatory because many PAH compounds are known or suspected to be toxic, mutagenic or carcinogenic (Patnaik 1992). Therefore, PAHs are considered to be environmental pollutants that can have a detrimental effect on the flora and fauna of affected habitats, resulting in the uptake and accumulation of toxic chemicals in food chains which cause serious health problems and/or genetic defects in humans. The high molecular weight (HMW) PAHs (four or more fused rings) are of particular environmental concern, because of their potential mutagenicity and carcinogenicity (Goldman et al. 2001). On the basis of their abundance and toxicity, 16 PAH compounds have been identified by the U.S. Environmental Protection Agency (EPA) as priority pollutants (Keith and Telliard 1979) of which chemical structures are shown in Figure 1. © 2007 Springer-Verlag Berlin Heidelberg.