Biodegradation of naphthenic acids by Rhodoccocus spp.

Naphthenic acids (NAs) are an important group of organic pollutants comprised predominantly of saturated aliphatic and alicyclic carboxylic acids. Although these compounds are toxic, recalcitrant, and persistent in oil sands deposits, we are just learning the diversity of microorganisms involved in NAs-degradation and the mechanisms by which NAs are biodegraded. Here, we described the ability of Rhodococcus sp. BCP1 and Rhodococcus opacus R7 to utilize two model naphthenic acids (NAs) i.e. cyclohexancarboxylic acid (CHCA) and cyclopentanecarboxylic acid (CPCA) as sole carbon and energy source. BCP1 strain degraded both the NAs with higher rates compared to R7; moreover, CHCA was shown to be metabolized faster than CPCA by both the Rhodococcus spp. Furthermore, genes coding for enzymes putatively involved in β-oxidation metabolism were identified in BCP1 genome. RT-PCR experiments showed that all these genes are induced by the growth of BCP1 on either CPCA or CHCA. These results suggest their involvement in β-oxidation metabolism of NAs by R. sp. BCP1.