Anaerobic degradation of non-substituted aromatic hydrocarbons

Aromatic hydrocarbons are among the most prevalent organic pollutants in the environment. Their removal from contaminated systems is of great concern because of the high toxicity effect on living organisms including humans. Aerobic degradation of aromatic hydrocarbons has been intensively studied and is well understood. However, many aromatics end up in habitats devoid of molecular oxygen. Nevertheless, anaerobic degradation using alternative electron acceptors is much less investigated. Here, we review the recent literature and very early progress in the elucidation of anaerobic degradation of non-substituted monocyclic (i.e. benzene) and polycyclic aromatic hydrocarbons (PAH such as naphthalene and phenanthrene). A focus will be on benzene and naphthalene as model compounds. This review concerns the microbes involved, the biochemistry of the initial activation and subsequent enzyme reactions involved in the pathway.

► Anaerobic benzene and naphthalene degradation is performed by microbes belonging to different phyla. ► Metabolite analysis of cultures suggest as initial activation reaction either methylation, hydroxylation, or carboxylation for benzene, and methylation or carboxylation for naphthalene. ► Proteogenomic studies indicate carboxylation of benzene and naphthalene. ► Non-substitute aromatic hydrocarbons are most likely activated by a novel carboxylation reaction.