The Response Of Indigenous Microbial Community On Exogenous Bisphenol A And The Biodegradation Machanism Of Bisphenol A

With the development of industry,more and more attention was paid to the pollution and protection of environment.As a member of endocrine disrupting chemicals(EDCs),bisphenol A(BPA)is widely used in the synthesis of epoxy resins and polycarbonate plastics.It was detected in the river and sediment all over the world.Many studies focused on the effects of BPA on environment and the methods to deal with BPA pollution.In this paper,sediment was spiked with BPA solution to explore the interaction between indigenous microbial communities and BPA biodegradation in sediment.In this study,the research included the following two parts.Firstly,we investigated the process that BPA adsorbed to the sediment and its effects on microbial communities.Sterilized sediment was spiked with 10 mg/L and 50 mg/L BPA,and we found that adsorption rates of BPA in systems with 10 mg/L and 50 mg/L BPA reached to 61.8%and 33.9%on the 2 hours,respectively.Molecular biological technique was used to explore the variation of microbial communities.Quantitative polymerase chain reaction analysis(QPCR)indicated that BPA promoted the abundance of bacteria and fungi comparing with controls,and the promotion effects was more significant by low concentration of BPA.Denaturing gradient gel electrophoresis analysis(DGGE)reflected that the bacterial communities changed significantly in the process.After one day of incubation,the diversity index of microcosm increased significantly from 2.06 to 2.99 in the control,while they remained 2.3 and 2.07 in treatments with low and high concentration of BPA,respectively,this indicated that BPA decreased the diversity of bacterial community on the early stage.According to the Dice coefficient analysis,BPA could change the microbial communities depending both on BPA concentration and incubation time.On the late stage,despite the little difference on microbial diversity,BPA affected microbial community by increasing some species which might resistance to BPA or further participate in BPA biodegradation,and inhibiting others those sensitive to BPA.Secondly,we investigated the biodegradation mechanism of BPA in the terms of microbes and enzymes.Biodegradation rates of BPA in systems with 10 mg/L and 50 mg/L BPA reached to 64.3%and 61.8%on the first day,respectively,and over 84%of the BPA was removed in both systems after 4 days.The DGGE bands which were of high relative intensities and shifted obviously in intensity during the experiment were excised for sequencing.Pseudomonas and Sphingomonas presented over 73%of the total bacteria.After one day of incubation,Pseudomonas and Sphingomonas in BPA stressed samples still presented over 56%,while they reduced rapidly and only presented 19.2%of the total bacteria in treatment A.Thus,BPA promoted Pseudomonas and Sphingomonas,and BPA also inhibited other competitors.We also found both laccase and polyphenol oxidase(PPO)activity increased first and declined later.Besides,laccase activity was positive related to the biodegradation rate of BPA,thus,we speculated that laccase was related to the degradation of BPA.PPO activity reached to a maximum value on day 2,which was later than the time for laccase activity peak.Besides,PPO activity remained the high level from day 2 to day 4.We speculated that PPO might contribute to the degradation of BPA and metabolic intermediates.