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 mixture s of five polycyclic aromatic hydrocarbons (PAH), phenanthrene, fluorene, a nthracene, 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 o f these strains were studied and their effects on the kinetics and the bala nce of degradation were characterised. Competition between PAH and degradat ion by cometabolism were frequently observed. Mixed cultures of two or thre e strains, although possessing the global capacity to mineralise the set of five PAH, achieved limited degradation of the mixture. In contrast, a cons ortium from a PAH-contaminated soil readily mineralised the five-PAH mixtur e. The results suggested that soil consortia possessed a wider variety of s trains capable to compensate for the competitive inhibition between PAH as well as specialised strains that mineralised potentially inhibitory PAH met abolites produced by cometabolism.