Selective Aerobic Degradation of Methyl-Substituted Polycyclic Aromatic Hydrocarbons in Petroleum by Pure Microbial Culturest

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Abstract
Studies of laboratory degradation of Arabian light crude oil (b.p. < 200°C) by pure cultures of bacterial strains Pseudomonas sp. isolated from tanker ballast waters showed that biodegradation of alkyl-substituted polycyclic aromatic hydrocarbons strongly depends on the number, position, and the type of the substituents. Biodegradation of alkylphenanthrenes and dibenzothiophenes decreased with increasing number of substitutents. Biodegradation of methylphenanthrenes (P), dibenzothiophenes (DBT), pyrenes (Py) and chrysenes (C) showed a pattern similar to that previously observed for the methylnapthalenes; compounds containing unsubstituted α and β adjacent positions were more readily degraded. Thus, 2- and 3-MP, 2- and 3-MDBT, 1-MPy and 2- and 3-MC were shown to be less resistant to degradation within these families. Cycloalkylaromatics, such as partially aromatized steranes, hopanes and 8, 14-secohopanes were generally resistant to degradation by the cultures employed.