Rhodococcus sp. strain FG-mediated biodegradation of biphenyl and its di(chloro/hydroxy)-substituted derivatives diminishing the immuno- and hepatotoxic potential of the pollutants.

Polychlorinated biphenyls (PCBs), a group of compounds consisting of 209 congeners with one to ten chlorine substituents, are known to be among the persistent organic pollutants (POPs) listed by the Stockholm Convention; and a significant amount of PCBs-related scientific research has predominantly been focused on adverse effects caused by the medium- and high-chlorinated PCB congeners. The present study demonstrates that biphenyl and PCB 12 (3,4-dichlorobiphenyl) caused humoral immuno-suppression upon entering a mammal organism. On the other hand, a mixture of 3-hydroxy-4-chlorobiphenyl and 4-hydroxy-3-chlorobiphenyl (constitute 98.42 % of the Mixture A) did not cause immunotoxic effect. All the substances under study triggered chronic hepatitis in mice. The use of bacterial destructors can solve the issue of contamination of mammal organisms with these compounds. From POPs-contaminated soil, a bacterial strain Rhodococcus sp. FG1 was isolated, which degrades effectively biphenyl, PCB 12 and Mixture A. It was found that Rhodococcus sp. FG1-mediated biodegradation of biphenyl, PCB 12 and Mixture A resulted in a decrease in the health risk indicators down to the safe values: over the entire range of studied compounds, the non-carcinogenic hazard index (HI) was below unity, and the carcinogenic risk index (CR) was less than the threshold value of 10-6. Peroral ingestion of the biodegradation products did not cause statistically significant alterations in the immune processes in the mouse body, and the manifestation of negative effects on the liver was reduced considerably. Therefore, our study makes a significant contribution to providing insight on the issues related to the detrimental effects of unsubstituted biphenyls on the health of mammals, and the obtained results show promise for the bacterial destructors to be applied for mitigating these effects.