Chapter 13:Anaerobic Pathways for the Catabolism of Aromatic Compounds

Removal of aromatic compounds, which mostly derive from the polymer lignin, fossil fuel reservoirs, and industrial activities, is very important both for a balanced global carbon budget and to protect natural ecosystems and human health from the toxic effect of some of these environmental pollutants. Whereas the aerobic catabolism of aromatic compounds has been extensively studied for many decades, the anaerobic catabolism is a more recently discovered and so far poorly characterized microbial capacity despite the fact that anoxic conditions dominate in many natural habitats and contaminated sites. The anaerobic catabolism of aromatic compounds by some specialized bacteria becomes, thus, crucial for the biogeochemical cycles and for the sustainable development of the biosphere. Moreover, anaerobic degradation of aromatic compounds involves various intriguing biochemically unprecedented reactions that are also of great biotechnological potential as alternatives to the current synthesis processes and for the anaerobic valorization of aromatic compounds to produce biofuels, biopolymers, and commodity chemicals. In this chapter we summarize the major degradation pathways and the associated cellular responses when bacteria grow anaerobically in the presence of aromatic compounds. The unexplored potential and some biotechnological applications of the anaerobic catabolism of aromatic compounds are also discussed.