Degradation Characteristics Of BDE-47 Aerobic Degrading Bacteriaand Degradation Mechanism Research

Polybrominated diphenyl ethers(PBDEs)are a kind of global brominated flame retardants that are widely found in nature and pose a great threat to human health and ecological safety.Zhejiang Province is one of the provinces and cities with the most intensive e-waste dismantling in China.E-waste contains a large number of harmful substances such as PBDES,which has become an important pollution source of surrounding environmental media.In this paper,the highly biotoxic 2,2 ',4,4'-tetrabrominated diphenyl ethers(BDE-47)were used as representative pollutants of PBDES to screen out BDE-47 aerobic degrading bacteria.The growth characteristics of WX-1 and the effects of different culture conditions on the degradation of the strain were studied,and the degradation efficiency of intracellular enzymes and extracellular enzymes of the strain was investigated.The intermediate products in the degradation process of BDE-47 were detected to analyze the degradation mechanism.1.This study took the soil around an electronic waste dismantling industrial park in Zhejiang Province as the main research object,domesticated and separated cultivable microorganisms,and obtained 3 strains with BDE-47 as the sole carbon source for growth and metabolism degradation through re-screening.Bacteria,through morphological observation,physiological and biochemical experiments and molecular biology identification: WX-1 is Rhodococcus ruber,WX-2 is Gordonia sp.,WX-3 is identified as copper greedy bacteria(Cupriavidus necator).The degradation ability of WX-1,WX-2,and WX-3 strains after 7 days of culture was determined.The degradation rates of the three strains ranged from 46.69% to 62.41%,respectively.WX-1 has the strongest degradation ability,and the degradation rate of BDE-47 can reach 62.41% within 7 days.2.Determine the growth and degradation characteristics of WX-1 degrading bacteria: In the inorganic salt medium with BDE-47 as the sole carbon source,the p H is6.0?7.0,the temperature is 30??35?,and the concentration of BDE-47 is Between300 and 800 ?g/L,when the inoculation amount is 1% to 3%,the strain is active and grows well.Orthogonal experiment results show that the optimal growth conditions for WX-1 are: 30°C,p H=7.0,the initial concentration of BDE-47 is 500 ?g/L,and the inoculation amount is 1%;WX-1 degrading bacteria is at 35°C,p H= 7.0,inoculation amount of 5%,500 ?g/L BDE-47 degradation system has the best degradation effect.3.Detect the degradation effect of crude enzyme solution and extracellular crude enzyme solution on BDE-47.The results show that the intracellular enzyme plays a major role in the enzymatic degradation process,and the degradation effect reaches the best on the 3rd day.GC-MS and LC-MS were used to determine the degradation products of BDE-47.During the degradation of BDE-47 by WX-1,one debromination product,three hydroxylation degradation products and one bromophenol product were detected.According to 2,4,4'-tribromodiphenyl ether(BDE-28),6-hydroxy-2,2',4,4'-tetrabromodiphenyl ether(6-OH-BDE-47),5-Hydroxy-2,2',4,4'-tetrabromodiphenyl ether(5-OH-BDE-47),2'-hydroxy-2,4,4'-tribromodiphenyl ether(2'-OH-BDE-28)and2,4-dibromophenol(2,4-DBP)are five degradation products,and three possible degradation pathways are deduced.The degradation process of BDE-47 by strain WX-1is mainly hydroxylation reaction Mainly.