Bitumen extraction from the oil sands deposits in northern Alberta produces large volumes of process-affected water, which must be treated prior to release into the environment. Previous research has shown that this process-affected water is highly toxic to aquatic organisms. The acute toxicity of this has been shown to be primarily due to a diverse group of cyclic and non-cyclic carboxylic acids known as the naphthenic acids (NA’s). The primary removal mechanism of NA’s is by microbial degradation.

Enrichment cultures obtained from a naphthenic acid contaminated tailings pond, using minimal media and decahydronaphthoic acid (DHNA, a bicyclic NA surrogate) as the sole carbon source resulted in the isolation of a bacterium able to grow on cyclohexane carboxylic acid (CCA, a monocyclic NA surrogate) and DHNA as their sole carbon source. Classical identification techniques identified this organism as a Pseudomonas species. PCR using primers flanking the hypervariable region of the 16S rRNA gene followed by sequencing identified it as Pseudomonas putida. Incubation of P. putida strain P5 with ¹⁴C-DHNA labeled on the ring distal to the carboxylic acid group resulted in no ¹⁴CO2 evolved, indicating inability to cleave the second ring. Radio-TLC analysis of culture and medium ethyl acetate extracts revealed a highly polar terminal metabolite in addition to the parent compound. These results indicate that although P. putida P5 is unable to mineralize DHNA; it is able to partially metabolize it to a more polar compound, possibly via a Baeyer-Villiger type reaction.