Microbial Degradation of Alkyl Carbazoles in Norman Wells Crude Oil

Norman Wells crude oil was fractionated by sequential alumina and silicic acid column chromatography methods. The resulting nitrogen-rich fraction was analyzed by gas chromatography-mass spectrometry and showed 26 alkyl (C(1) to C(5)) carbazoles to be the predominant compounds. An oil-degrading mixed bacterial culture was enriched on carbazole to enhance its ability to degrade nitrogen heterocycles. This culture was used to inoculate a series of flasks of mineral medium and Norman Wells crude oil. Residual oil was recovered from these cultures after incubation at 25 degrees C for various times. The nitrogen-rich fraction was analyzed by capillary gas chromatography, using a nitrogen-specific detector. Most of the C(1)-, C(2)-, and C(3)- carbazoles and one of the C(4)-isomers were degraded within 8 days. No further degradation occurred when incubation was extended to 28 days. The general order of susceptibility of the isomers to biodegradation was C(1) > C(2) > C(3) > C(4). The carbazole-enriched culture was still able to degrade n-alkanes, isoprenoids, aromatic hydrocarbons, and sulfur heterocycles in the crude soil.