Cadmium-induced stress response of Phanerochaete chrysosporium during the biodegradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47).

Cd-induced stress response of Phanerochaete chrysosporium during the biodegradation of BDE-47 was investigated in this study, with the goal of elucidating the tolerance behavior and the detoxification mechanisms of P. chrysosporium to resist the Cd stress in the course of BDE-47 biodegradation, which has implications for expanding the application of P. chrysosporium in the bioremediation of Cd and BDE-47 combined pollution. The results suggested that single BDE-47 exposure did not induce obvious oxidative stress in P. chrysosporium, but coexistent Cd significantly triggered ROS generation, both intracellular ROS level and H2O2 content showed positive correlation with Cd concentration. The activities of SOD and CAT were enhanced by low level of Cd (≤ 1 mg/L), but Cd of higher doses (＞1 mg/L) depressed the expression of these two antioxidant enzymes at the later exposure period (3–5 days). The intracellular content of GSH along with GSH/GSSG ratio also exhibited a bell-shaped response with a maximum value at Cd of 1 mg/L. Furthermore, Cd-induced ROS generation resulted in the lipid peroxidation, as indicated by a noticeable increment of MDA content found after 3 days. Moreover, the study also indicated that Cd less than 1 mg/L promoted the production of extracellular protein and quickened the decrease of pH value in the medium, while excessive Cd (＞1 mg/L) would lead to inhibition. These findings obtained demonstrated that P. chrysosporium had a certain degree of tolerance to Cd within a specific concentration range via regulating the antioxidant levels, inducing the synthesis of extracellular protein as well as stimulating the production of organic acids, and 1 mg/L is suggested to be the tolerance threshold of this strains under Cd stress during BDE-47 biodegradation.