Microbial degradation of polycyclic aromatic hydrocarbons and polycyclic aromatic nitrogen heterocyclics

Fermentor studies were conducted to examine the microbial degradation of polycyclic aromatic hydrocarbons (PAHs; naphthalene, phenanthrene, anthracene) and a polycyclic aromatic nitrogen heterocyclic (quinoline) using a mixed bacterial culture capable of utilizing these compounds as the sole carbon and energy source for growth. Half‐lives for the three PAHs in the cyclone fermentor system ranged from 1 day for naphthalene to 4 days for anthracene. Several major metabolites during the biodegradation of PAHs were also identified. These included 2‐hydroxybenzoic acid and 1‐naphthalenol (for naphthalene); 1‐phenanthrenol and 1‐hydroxy‐2‐naphthalenecarboxylic acid (for phenanthrene); and 3‐hydroxy‐2‐naphthalenecarboxylic acid (for anthracene). Thus our bacterial culture biodegraded the three PAHs by initial hydroxylation of the molecule followed by the eventual cleavage of the ring to yield the ortho‐ or meta‐cleavage intermediates, which would be further metabolized via conventional metabolic pathways. However, biodegradation of the nitrogen‐containing polycyclic aromatic hydrocarbon compound quinoline by our culture resulted in the accumulation of 4–5 metabolites, one of which has been identified as 2‐quinolinol. Work is in progress to identify the other metabolites from quinoline degradation.