Isolation, Identification And Degradation Characteristics Of Bis (2 - Ethylhexyl) Phthalate Degrading Bacteria

Phthalic acid esters(PAEs, also known as phthalate) are a kind of widely used synthetic organic compounds, which are mainly used as plasticizer, painting, coating and other industries.Among a large amount of common PAEs, di(2-ethylhexyl)phthalate(DEHP) is most widely used. DEHP is easily released and transfered into the environment. Studies show that DEHP has a estrogenic effect. Its toxicity can cauce carcinogenic, teratogenic and mutagenic effect.Therefore DEHP has been classified as "priority pollutant".Biological degradation becomes an important way in DEHP degration.The aim of this study is to isolate a strain with DEHP degrading efficient from polluted environment by DEHP, and to study its related properties, in order to provide a theoretical reference and bacterium source for the environment remediation contaminated by DEHP.(1) Using gradient pressure domestication method,we isolated a strain of DEHP degrading bacterium from a place of petroleum contaminated soil in the city of Heze in Shandong province,which was named as YC-RL4. Strain YC-RL4 was determined as a bacillus of Mycobacterium confluentis and gram-positive by Gram staining method, observing in electron microscope and Biolog identification.(2) By single factor experiments we obtained the optimum degradation conditions of strain YC-RL4 in DEHP degrating reaction :the optimum pH for degrating is 9,the optimum pH for cell growth is 8; the optimum temperature for degrating is 20℃,the optimum temperature for cell growth is 30℃; The ideal growth and DEHP degraing concentration of NaCl for strain YC-RL4 is 3% and the highest salinity tolerance ability is 7%.Through the maximum tolerance test, we obtain the maximum concentration of DEHP which strain YC-RL4 can resistant to is 700-800mg/L.(3) Substrate spectrum experiments explained that strain YC-RL4 can degrate many chemical compounds in similar with DEHP, which suggested that strain YC-RL4 has a wide range of degrating substrates and a strong ability to adapt to the environment. In terms of biodegradation to various pollutants,strain YC-RL4 has a great applicating potential.(4) Fermentation experiments proved that strain YC-RL4 can utilize DEHP as a sole carbon source to grow,and can produce acidic metabolites in the reaction process,which provided basis for the industrial application of the strain in the future.(5) We detected the degration amount of DEHP by strain YC-RL4 under different initial concentration of DEHP and at different reaction time.Thus we could give an assertion that the biodegradation reactions of DEHP by strain YC-RL4 were in accordance with the first order kinetic model.(6) By collecting the metabolites of strain YC-RL4 at different time points in the reaction of DEHP degration,which were detected by HPLC-MS aferwards,a degradation pathway of DEHP was deduced,which provided a theoretical reference for the further study of degradation mechanism.