[Microbial degradation of 2, 2', 4, 4'-tetrabrominated diphenyl ether under anaerobic condition]

Polybrominated diphenyl ethers are emerging contaminants in the environment, among which 2, 2' 4, 4'-tetrabrominated diphenyl ether (BDE-47) is one of the most frequently detected and the most toxic to organisms. Using BDE-47 as the object, this study investigated the degradation of BDE-47 by six enriched cultures containing Dehalococcoides species. The purpose is to understand the microbial degradation of BDE-47 under anaerobic condition and its kinetics. Serum bottles of 100 mL were used to construct the microcosms and enrich the anaerobic microorganisms. For each culture, two treatments were performed. One used BDE-47 as the only energy source with the designed concentration of 200 microg x L(-1), and the other used both BDE-47 and trichloroethene (TCE) as the energy source with the designed concentrations being 200 microg x L(-1) and 13 mg x L(-1), respectively. After three months of experiment, two enriched cultures (6M6B and T2) could obviously degrade BDE-47, producing BDE-17 and BDE-4 (and small amount of DE). The presence of TCE inhibited the degradation of BDE-47 by 6M6B and T2 cultures to a certain degree. The PCR-DGGE assay was performed to compare the microbial community structure of various enrichments and it was found that Acetobacterium sp. had good correlation with the degradation of BDE-47. Under three different initial BDE-47 concentrations (50 microg x L(-1), 250 microg x L(-1) and 500 microg x L(-1)), the degradation rates of BDE-47 were 0.003 3, 0.001 4 and 0.001 0 d(-1), respectively. This study demonstrated that BDE-47 could be reductively degraded by bacteria under anaerobic condition, producing BDE-17 and BDE-4. Acetobacterium sp. might play an important role in the degradation of BDE-47. High concentration of BDE-47 might inhibit the activity of the BDE-47 degrading bacteria to a certain degree.