Efficiency of defined strains and of soil consortia in the biodegradation of polycyclic aromatic hydrocarbon (PAH) mixtures

The microbiological characteristics of the bacterialdegradation of mixtures of five polycyclic aromatichydrocarbons (PAH), phenanthrene, fluorene,anthracene, fluoranthene and pyrene, wereinvestigated. Three pure bacterial strains using oneor several of these PAH as carbon sources wereselected. The interactions between PAH during thedegradation of PAH pairs by each of these strains werestudied and their effects on the kinetics and thebalance of degradation were characterised. Competitionbetween PAH and degradation by cometabolism werefrequently observed. Mixed cultures of two or threestrains, although possessing the global capacity tomineralise the set of five PAH, achieved limiteddegradation of the mixture. In contrast, a consortiumfrom a PAH-contaminated soil readily mineralised thefive-PAH mixture. The results suggested that soilconsortia possessed a wider variety of strains capableto compensate for the competitive inhibition betweenPAH as well as specialised strains that mineralisedpotentially inhibitory PAH metabolites produced bycometabolism.