Biodegradation studies of polyaromatic hydrocarbons in aqueous media

Sixteen bacterial strains isolated from an activated sludge and Mycobacterium ssp. PYR-1 were tested for their ability to degrade polyaromatic hydrocarbons (PAHs). The bacterial strains Pasteurella ssp. (B-2) and Mycobacterium ssp. PYR-1 (AM) showed a high biodegradation potential of three- and four-ring PAHs. Bacterial strain AM was able to degrade up to 80% of three and four-ring PAHs (phenanthrene, fluoranthene and pyrene) within the first month of incubation, while the bacterial strain B-2 achieved the same biodegradation in 2 months. The metabolic pathway of PAH degradation was studied using fluoranthene and the bacterial strain AM. Ninety per cent of fluoranthene was biodegraded within the first 9 d of incubation when applied as a single substrate. Retention factor values from thin-layer chromatography studies, gas chromatography with mass selective detection and tandem mass spectrometry identified 9-fluorenone-1-carboxylic acid as one of the stable metabolic products and from this a fluoranthene biodegradation pathway is proposed.