Phthalate Esters Biodegradation Characteristics And Degradation Pathways Of Bacillus Mojavensis B1811 And Burkholderia Pyrrocinia B1213

Phthalate esters?PAEs?are mainly used as plasticizers in the plastics industry.They are listed as priority pollutants due to theirs environmental endocrine by the China Environmental Monitoring Station and the US Environmental Protection Agency.The presence of PAEs was extensively detected in soils,rivers,lakes,marine sediments,drinking water,landfills,and food in major industrial countries worldwide.Compared with non-biodegradation of PAEs,biodegradation is the main way to eliminate the PAEs in the environment.This study investigated biodegradation characteristics and biodegradation pathways of seven PAEs?DMP,DEP,DBP,BBP,DPP,DNOP,DEHP?which were listed as priority pollutants by US Environmental Protection Agency.Bacillus mojavensis B1811 and Burkholderia pyrrocinia B1213 were previously isolated from soil in our laboratory and had been deposited in China General Microbiological Culture Collection Center.The aim of this study is to provide new strains and theoretical basis for bioremediation of pollutants containing phthalate esters.The main content and conclusions of this study are as follows:?1?The results of seven PAEs utilization tests by strain B1811 and strain B1213 with shaking conditions showed that seven PAEs could be efficiently utilized by strain B1811,while DEHP and DNOP could be efficiently utilized by strain B1213.Meanwhile,effects of different environmental factors on PAEs biodegradation were studied and the optimal conditions of PAEs biodegradation of two strains were found.The results showed that 210 rpm,pH 6.0-9.0 and 40?were optimal conditions for PAEs with long alkyl chains?DEHP?DNOP?DPP?BBP?DBP?degradation by starin B1811,and 180 rpm,pH 8,30?and1%yeast extract were optimal conditions for PAEs with short alkyl chains?DMP?DEP?degradation by starin B1811.As for strain B1213,the optimal conditions for DEHP degradation were 180 rpm,30?,pH 7and 1%yeast extract.?2?Kinetics of PAEs biodegradation by strain B1811 and strain B1213 were investigated by studying the relationship between initial substrates concentrations and biodegradation time of PAEs using SPSS and Matlab software.The results showed that t_1/2/2 were all within 20 h?except DBP and BBP?when the initial concentrations of PAEs were 100 mg/L during the PAEs degradation by strain B1811.With the increase of initial DEHP concentrations during the degradation by strain B1213,the lag phase time increased from 16 h to 66 h and the maximum substrate transformation rate increased from 3.4 mg/L/h to17.46 mg/L/h.When the initial concentration of DEHP was above 700 mg/L,the maximum substrate transformation rate of strain B1213 decreased dramatically and the lag phase time remained relatively long?64.99 h?.?3?High performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry?HPLC-ESI-QTOFMS?was applied to identify the major metabolites of seven PAEs and the biodegradation pathways of seven PAEs were deduced based on the metabolites.As for strain B1811,the PAEs were firstly degraded to corresponding phthalate monoesters and then phthalic acid,phthalic acid was rapidly degraded to produce benzoic acid which was subsequently converted to PCA and ultimately transformed to CO₂ and H₂O.Regarding the DEHP degradation pathway of strain B1213,DEHP was firstly degraded to MEHP.The alkyl side chain of MEHP was eliminated to form MBP and MBP was degraed to form PA,PA was eventually converted to CO₂ and H₂O via 3-oxo-Hexanoic acid.