Biodegradability of hydroxylated derivatives of commercial polychlorobiphenyls mixtures by Rhodococcus-strains

• The interactions of HO-PCBs mixtures with the Rhodococcus strains were studied. • The HO-PCBs mixtures cause a toxic effect on the growth of Rhodococcus strains. • The bacterial strains can use HO-PCBs as a source of carbon. • The metabolites of the destruction of HO-PCBs by Rhodococcus -strain are biodegradable. • The studied strains are effective for remediation of PCB-contaminated areas. For the first time, investigations are is carried out for the interactions of hydroxylated polychlorobiphenyls (HO-PCBs) mixtures, which were obtained from PCBs commercially available under the trade name Sovol, with the Rhodococcus (R.) strains. It is established that the HO-PCBs mixtures containing basic products within the range of 83.2–95.8% cause a toxic effect on the growth of R. wratislaviensis KT112-7, R. wratislaviensis CH628, R. ruber P25 strains. The inhibitory concentration (IC50) was varied within the range of 30–490 mg/l. For the first time, it is found that the bacterial strains can use HO-PCBs as a source of carbon with no co-substrate added. The strains are shown to degrade 95.5–100% of the HO-PCBs mixtures at a concentration of 0.1 g/l during 14 days. It is demonstrated that HO-PCBs degrading occurs following the classical bacterial pathway of transforming biphenyl/PCB. However, the HO-PCBs metabolites, which are substituted benzoic acids, are not the final products of the transformation and are subjected to further degrading by the strains. Therefore, the R. wratislaviensis KT112-7, R. wratislaviensis CH628, and R. ruber P25 strains are shown to degrade the HO-PCBs mixtures efficiently and are found to be stable to their toxic action.