Bioremediation mechanisms of chlorophenol-Cr(Ⅵ): The role of amines, immobilization, and DEGs in Pseudomonas sp. PC

Abstract

The combined pollution of p-Chlorophenol (4-CP) and hexavalent chromium [Cr(VI)] is widespread in the environment. However, little information is available on the relationship between the fate of Cr(VI) and its amines during dechlorination, which are dominant in pH value changes. Here, Pseudomonas sp. PC can degrade 4-CP and convert Cr(VI). The removal efficiency of Cr(VI) accords with the first-order reaction kinetics. Notably, the pH value (7.95) of the chlorophenol-Cr(VI) systems increased compared to the 4-CP treatment due to the significant accumulation of amines, especially ethambutol, which was 1.06 folds higher than 4-CP treatment. The pH value of the 4-CP treatment decreased to 5.89. Thus, Cr(III) was more likely to immobilize on the surface of the cell in the form of Cr(OH)3. Interestingly, Catechol 1,2-dioxygenase (catA) was 0.98 folds higher than Catechol 2,3-dioxygenase (dmpB) in chlorophenol-Cr(Ⅵ) systems, indicating that the presence of Cr(Ⅵ) changed the metabolic pathway of Pseudomonas sp. PC for 4-CP from the dmpB meta-cleavage pathway to the catA ortho-cleavage pathway. These conclusions deepen the cognizance of the relationship between the degradation pathway of chlorophenols, the fixation of Cr(VI) and the amines, providing a better basis for the bioremediation application of chlorophenol-Cr(VI) sites.