Screening,Characteristics And Degradation Pathway Of 2,2',4,4'-Tetrabromodiphenyl Ether Aerobic Degrading Bacteria

Polybrominated diphenyl ethers(PBDEs)are a kind of environmentally persistent organic pollutants widely present in nature,which are bioaccumulative,semi-volatile and highly biotoxic.PBDEs theoretically have 209 congeners,and BDE-47(2,2',4,4'-tetrabromodiphenyl ether)is one of the most widely distributed and most toxic to PBDEs congeners.Zhejiang Province is one of the provinces and cities with the most intensive dismantling of electronic waste in our country.BDE-47 and other harmful substances contained in electronic waste have become an important source of pollution to the surrounding environmental media.Study the background value of BDE-47 contaminated soil,select BDE-47 degrading strains from it,optimize the degradation ability and growth characteristics of degrading bacteria,and explore their degradation pathway,It is beneficial to provide theoretical basis and technology for environmental restoration technologies such as bioremediation of BDE-47 polluted soil.In this study,the soil around an electronic waste dismantling industrial Park in Zhejiang Province as the main research object.A total of 5 different soil samples were collected,including the soil in the cable factory,the soil in the metal recycling plant,the soil near the metal company farmland,the street soil near the metal company,and the soil near the metal factory.Using of high-throughput sequencing technology to determine the bacterial community structure in the soil contaminated by BDE-47 in an electronic waste dismantling industrial park in Zhejiang Province.The results showed that 21 bacteria were detected.Proteobacteria,Acidobacteria,and Actinobacteria were the main dominant bacteria.Sphingomonas can be regarded as the dominant bacterium in five soils.The soil physical and chemical properties of 5 soils were measured.As a result,the soils in densely populated areas were mostly acidic,and the street soils were alkaline.Compared with other sample soils,farmland soils have better chemical properties and are more conducive to crop growth.The cultivable microorganisms were domesticated and separated by traditional microbial culture,three degradation strains capable of growing with BDE-47 as the sole carbon source were obtained through rescreening.The results of morphologicalobservation,physiological and biochemical characteristics,and molecular biological identification results collectively show that: GB-1 is Bacillus sp.,GB-2 is Acinetobacter sp.,And GB-3 is Rhodococcus sp..The degradation ability of GB-1,GB-2,and GB-3strains after 8 days of culture was measured.The degradation rates of the three strains of degrading bacteria ranged from 55%~80%.The degradation ability of GB-3 degrading bacteria is the strongest,and the degradation rate can reach 79.5% in 8 days.The growth characteristics of GB-3 degrading bacteria were determined through experiments: In the LB medium,the strain quickly entered the logarithmic growth phase in the early stage of growth.After 30 h,the growth tended to be flat,after 66 h,it entered the stable phase,and after 102 h,it entered the decay phase.In an inorganic salt medium with BDE-47 as the sole carbon source,When the pH is 7,the rotation speed is150 r/min,the concentration of BDE-47 is between 50~200 ?g/L,and the temperature is between 30?and 35?,the strain has strong activity and good growth.The orthogonal test results showed that the optimal growth conditions of GB-3 degrading bacteria were:temperature 30?,pH=7,rotation speed 150 r/min,and initial BDE-47 concentration was 100 ?g/L.Analysis of BDE-47 degradation products by HPLC-Orbitrap,During the degradation of BDE-47 by strain GB-3,6-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),2'-hydroxy-2,4-dibromo-diphenyl ether(2'-OH-BDE-7),2'-hydroxy-4-monobromodiphenyl ether(2'-OH-BDE-3),and 2,4-dibromophenol(2,4-DBP),six degradation products,three possible degradation pathways were deduced.It was found that the degradation process of strain GB-3 to BDE-47 was mainly hydroxylation.