Anaerobic Degradation of Aromatic Compounds

Abstract

The benzene ring moiety is found in biological compounds accounting for ~25% of the land-based organic matter on Earth. Hence, the biosynthesis and biodegradation of aromatic ring compounds constitutes an important part of natural carbon cycle. Microorganisms capable of using aromatic compounds as carbon and energy sources can be found in a range of very different habitats and redox conditions. In anoxic ecosystems where dissolved oxygen is depleted, degradation of aromatic compounds depends on the availability of inorganic electron acceptors such as nitrate, iron, sulfate or carbon dioxide. Developing efficient and effective bioremediation technologies requires an in-depth understanding of the microbial communities responsible for degradation of contaminants. Anaerobic microorganisms use a strategy of attacking the aromatic ring via reductive transformations. Anaerobic degradation of aromatic compounds (e.g. benzene, toluene and xylene (BTX), lignoaromatics, polycyclic aromatic hydrocarbons (PAHs) and halogenated aromatic compounds) has now been demonstrated under different redox conditions. One of the fundamental challenges has been to elucidate the microorganism(s) responsible for degradation of aromatic compounds in anaerobic environments. The recent advancements in molecular techniques have provided an opportunity to unravel the veil of the microbial activity responsible for the anaerobic degradation of aromatic compounds. This chapter provides an overview of some techniques and approaches to elucidate anaerobic degradation of aromatic compounds and how the active microorganisms can be identified, classified and enumerated.