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. 0 1992 John Wiley & Sons.