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

The microbiological characteristics of the bacterial degradation of mixtures of five polycyclic aromatic hydrocarbons (PAH), phenanthrene, fluorene, anthracene, fluoranthene and pyrene, were investigated. Three pure bacterial strains using one or several of these PAH as carbon sources were selected. The interactions between PAH during the degradation of PAH pairs by each of these strains were studied and their effects on the kinetics and the balance of degradation were characterised. Competition between PAH and degradation by cometabolism were frequently observed. Mixed cultures of two or three strains, although possessing the global capacity to mineralise the set of five PAH, achieved limited degradation of the mixture. In contrast, a consortium from a PAH-contaminated soil readily mineralised the five-PAH mixture. The results suggested that soil consortia possessed a wider variety of strains capable to compensate for the competitive inhibition between PAH as well as specialised strains that mineralised potentially inhibitory PAH metabolites produced by cometabolism.