Screening, Characteristics And Mechanism Of An Effective Decabromodiphenyl Ether Degrading Strain

A strain with high-efficiency in degrading decabromodiphenyl ether (BDE-209) wasisolated from sediment samples collected from Guiyu town in Guangdong Province, an e-wasterecycling area. To reveal the biodegradation efficiencies and mechanism, its degradationcharacteristics, changes of cellular microstructure, ions utilization and release during thedegradation processes of BDE-209, and analyse the distribution of BDE-209in degradingbacteria cells was investigated.The strain was identified as Brevibacillus brevis.The degradation efficiency of BDE-209at1.0mg/L by B. brevis reached54.38%within5d. The optimum conditions for BDE-209degradation were as follows: pH7, bacterial dosage3.0g/L, and culturing temperature30°C.The study also showed that the optimal strain age was36h and the best nitrogen source was(NH4)2SO4. B. brevis could tolerate the toxicity of Cu2+and Cd2+, although the presence of theseheavy metals posed certain influence on BDE-209degradation. As the concentration of Cu2+andCd2+were in the range of1.0~5.0mg/L and0.3~0.5mg/L, respectively, the degradationefficiency of BDE-209was still over50%.Cu2+and Cd2+in degradation system could induce cell adhesion, while the presence ofBDE-209could stimulate B. brevis cell growth. BDE-209promoted the release of ions and theinfluences on cation are more obvious than its effect on the anion. Detection of Br-proved thatdebromination occurred in the degradation process of BDE-209.B. brevis was of higher cell surface hydrophobic (CSH), which is benefit to the adhesionand degradation of BDE-209. CSH decreased with the elongated contact time due to theoccupation of hydrophobic region by BDE-209, and the addition of Cu2+and Cd2+could improvethe CSH descend range with the extension of time to some extent. BDE-209could increase thepermeability of cell membrane slightly, and the influence caused by Cu2+and Cd2+was moreremarkable. The permeability of cell membrane increased with the increasing concentration ofBDE-209and Cu2+.BDE-209was mainly accumulated on the cell membrane, and its changes of concentrationwith time in each phase showed a good linear relationship. The distribution process of BDE-209from aqueous phase to cell membrane and reverse distribution from cell membrane into cellcorrespond to Nernst distribution, which proved that BDE-209could across the cell membrane successfully and was degraded. The main toxicy demonstrated by BDE-209was membranetoxicity.