Modeling of the Biphenyl Dioxygenase α-Subunit Structure of Rhodococcus Strains and Features of the Destruction of Chlorinated and Hydroxylated Biphenyls at Different Temperatures

Based on modeling of the protein structure of the α subunit of biphenyl 2,3-dioxygenase (BphA1) (EC 1.14.12.18), the key enzyme for the destruction of biphenyl and polychlorinated biphenyls (PCBs), it was found that BphA1 Rhodococcus wratislaviensis KT112-7 (= VKM Ac-2623D) had the highest level of similarity with classical biphenyl dioxygenases (BDOs) of the PCBs-degrader strains of the genus Rhodococcus. The structure of BphA1 Rhodococcus wratislaviensis CH628 had the highest similarity with naphthalene dioxygenase of the strains of the genus Rhodococcus, and the structure of BphA1 Rhodococcus ruber P25 (= IEGM 896) was unique, since no protein molecules with a high level of similarity were identified. It was shown that all of the studied strains, despite their differences in the BphA1 structure, carried out dioxygenation of the unsubstituted ring in molecules of 3,4-dichlorobiphenyl (PCB 12), as well as monochlorinated and monohydroxy-monochlorinated biphenyls (mixture P). The level of destruction of PCB 12 and mixture P was 95.4–100% at 30°C for 10 days at an initial concentration of 0.1 g/L. It was found that a change in temperature (10–50°C) had the greatest effect on the biodegradative activity of the strain R. ruber P25 (a decrease by 3.1–3.9 times). R. wratislaviensis CH628 and R. wratislaviensis KT112-7 efficiently degraded PCB 12 at temperatures of 20–40 and 10–30°C, respectively (the destruction level was 93.2–100%).