Microbial Degradation of Alkyl Carbazoles in Norman Wells Crude Oil

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Abstract
Norman Wells crude oil was fractionated by sequential alumina and silicic acid column chromatography. The resulting N-rich fraction was analyzed by gas chromatography-mass spectrometry and showed 26 alkyl (C1-C5) carbazoles to be the predominant compounds. An oil-degrading mixed bacterial culture was enriched on carbazole to enhance its ability to degrade N 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.degree. C for various times. The N-rich fraction was analyzed by capillary gas chromatography, using a N-specific detector. Most of the C1-, C2- and C3-carbazoles and 1 of the C4-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 C1 > C2 > C3 > C4. The carbazole-enriched culture was still able to degrade n-alkanes, isoprenoids, aromatic hydrocarbons and S heterocycles in the crude oil.