Specific Features of Chlorinated Biphenyl Decomposition by Rhodococcus wratislaviensis Strain KT112-7 under High Salt Conditions

Abstract

Rhodococcus wratislaviensis strain KT112-7 (VKM As-2623D) degraded monosubstituted 2-/4-chlorobiphenyls (94.25 mg/L) and 2,4'-dichlorobiphenyl (22.3 mg/L) when the sodium chloride content in the culture medium did not exceed 50 g/L. We have calculated the kinetic parameters of chlorobiphenyl (CB) decomposition by the КТ112-7 strain, which demonstrated decreased decomposition efficiency with increasing NaCl concentration. A linear correlation has been found between the content of saturated, unsaturated, and branched fatty acids in the cell wall of the KT112-7 strain and the NaCl content in the culture medium. The change in the content and composition of fatty acids in the cell wall apparently led to a change in the permeability of the CB cell wall. R. wratislaviensis strain KT112-7 was able to oxidize the unsubstituted ring in 2-CB and 4-CB at all studied NaCl concentrations in the medium and efficiently decomposed the chlorobenzoic acids (CBAs) that formed as a result of the oxidation. Decomposition of 2,4'-CB at low NaCl concentrations in the medium (not higher than 10 g/L) involved the oxidation of the ring substituted by chlorine in the position 4, while the presence of 20–50 g/L of NaCl led to the oxidation of the ring substituted by chlorine in the position 2. The main detected metabolite was 2-chlorobenzoic acid in the former case and 4-chlorobenzoic acid in the latter. The 4-CBA transformation proceeded via the formation of protocatechuic acid (3,4-hydroxybenzoic acid) and catechol at all of the studied sodium chloride concentrations in the medium and through another pathway involving the formation of chlorocatechol at NaCl concentrations of 30, 40, and 50 g/L.