Property And Mechanism Of Tetrabromodiphenyl Ether (BDE-47) Biodegradation By Phanerochaete Chrysosporium

Polybrominated diphenyl ethers(PBDEs),as a kind of persistent organic pollutants(POPs),are ubiquitous in the environment.2,2',4,4'-tetrabromodiphenyl ether(BDE-47)has become the one of the most frequently detected PBDEs congener,and proved to be more toxic than other congeners.Thus,it has attracted widespread attention to explore efficient treatments to deal with BDE-47.In this study,Phanerochaete chrysosporium was selected to degrade BDE-47.The main works were conducted including investigating the BDE-47 biodegradation by fungus and extracellular enzyme,and illuminating biodegradation and oxidative stress mechanisms involved in BDE-47 degradation when cadmium co-existed.The optimum addition manner was determined that the spores of P.chrysosporium were preincubated for 3 d,and then pollutans were added into the system.Finally,the degradation rate reached 64.06% at the 5th d.The single factor experiment showed that the optimal conditions of BDE-47 degradation in water system was pH 5,BDE-47 0.5 mg L-1,inoculum dosage of spores 5%,glucose 5 mg L-1,reaction time 5 d.The distribution of BDE-47 in P.chrysosporium was explored.Subsequently intracellular and extracellular enzymes were exacted to degrade BDE-47,and it was found that the extracellular enzyme played an important role in the process of BDE-47 degradation.Effect of Cd2+ on BDE-47 biodegradation by P.chrysosporium and its extracellular were investigated.The results indicated that the degradation/adsorption efficiency was promoted at low concentration of Cd2+(?1 mg L-1),but inhibited at high levels(>1 mg L-1).While the ability of extracellular enzyme to deal with BDE-47 apparently decreased with Cd2+ concentration increasing.The phenomenon that the maximum activity occurred on the 3rd d was in accordance with the period of time,when the best degradation rate of BDE-47 by extracellular enzyme of P.chrysosporium achieved.After adding different concentrations of Cd2+,Mn P and LiP activity decreased markedly.These results suggested that Mn P and LiP participated in BDE-47 degradation process.Infrared scanning analysis indicated that the lipid and protein on the surface of fungus participated in BDE-47 degradation.LC-MS/MS analysis of degradation mechanisms demonstrated that the main products contained four mono-hydroxylated PBDEs(5-OH-BDE-47,4'-OH-BDE-17,6-OH-BDE-47,2'-OH-BDE-28)and two bromophenols(2,4-DBP,4-BP).It was inferred that the main aerobic transformation mechanisms of BDE-47 were hydroxylation and ether cleavage.Meanwhile,the major metabolites of BDE-47,bromophenol compounds,could be transformed or even mineralized by P.chrysosporium quickly.According to the results,three possible degradation pathways were proposed.Cd2+ had a suppressed impact on the generation amount of degradation products due to changing the property of fungus,but did not change the type of degradation products.P.Chrysosporium would be induced to produce ROS by BDE-47 and Cd2+.After the detection of MDA,SOD,CAT,GSH,extracellular protein,and pH,we found that Cd2+ at high concentration could pose negative impact on antioxidant ability and metabolism.This may was the primarily reason that high concentration of Cd2+ affected the degradation of BDE-47.