The presence of branching within an alkane interferes with b oxidation. Evidence for the anaerobic degradation of aliphatics is equivocal. Aromatic hydrocarbons such as benzene, toluene, ethylbenzene and xylene are predominate light petroleum fractions in gasoline. These compounds are also widely used as industrial solvents and synthetic intermediates. BTEX compounds are relatively water soluble and are a threat to ground water.
Aromatic hydrocarbons are toxic and carcinogenic.
The meta pathway yields acetyl-CoA and succinate, while the ortho pathway yields pyruvate, formate and acetaldehyde. Toluene and ethylbenzene can be oxidized by several pathways including the ortho and meta pathways and an aromatic carboxylic acid pathway depending on whether the initial oxidation is on the ring or the alkyl group. Anaerobic degradation occurs under denitrifying, sulfate reducing and methanogenic conditions. The ring is initially hydrogenated and it subsequently cleaved through a hydration reaction to yield aliphatic hydrocarbons which can be further metabolized. Polyaromatic Hydrocarbons .