Study On The Degradation Of Phthalic Acid Esters By Gordonia Terrae RL-JC02 And Its Mechanism

The toxicity and carcinogenicity of phthalate esters(phthalic acid esters,PAEs)have attracted more and more attention.PAEs is widely detected in different environmental media,even in remote polar regions such as the Arctic Circle.Because of its semi-volatilit y and hydrophobicit y,PAEs can be transported over long distances and remain in the environment.PAEs can remain in an anaerobic and nutrient deficient environment for many years.PAEs is the main component of plastic products,which can be easil y released into the environment during the production and use of plastics.In recent years,plastic film has been widel y used in agricultural production,so more and more PAEs has been released into farmland soil.The content of PAEs in some farmland soil in China is much higher than the control standard of PAEs compounds in American soil,so it is very necessary to remediate the soil contaminated by PAEs.di-(2-ethylhex yl)phthalate(DEHP)is a representative endocrine disrupting chemica l that is most widel y used as plasticizer.The toxicological effects of DEHP on environmental and human health have been widel y investigated.In this study,a novel DEHP degrading bacterial strain R L-JC02 was isolated from red soil with long-term usage of plastic mulch and strain R L-JC02 was identified as Gordonia terrae by 16 S r RNA gene anal ysis coupled with physiological and biochemical characterization.The degrading capacit y of different phthalic acid esters and related intermediates was investigated as well as the performance of strain RL-JC02 under different environmental factors.Strain R L-JC02 could degrade DEHP under a wide range of temperature,p H,salinit y and DEHP concentration.Speciall y,strain RL-JC02 showed good tolerance to low p H in which 8 6.6% of 50 mg/ L DEHP was degraded under the initial p H of 5.0 within 72 hours.In addition,strain RL-JC02 also had good tolerance to higher temperature,and the degradation effect remained at a high level when the culture temperature was 40 ?.The metabolic pathway of DEHP was proposed by metabolic intermediates identification via HPLC-MS anal ysis in which DEHP was hydrol yzed into phthalic acid(PA)and 2-ethylhexanol(2-EH)via mono(2-ethylhex yl)phthalate(MEHP).PA and 2-EH were further utilized through protocatechuic acid metabolic pathway and?-oxidation via protocatechuic acid and 2-ethylhexanoic acid,respectively.The application potential of strain RL-JC02 was confirmed through the bioremediation of artificial DEHP-contaminated red soil.The maximum d egradation percentage of DEHP(50 mg/kg)was 91.8% by strain RL-JC02 within 30 days' incubation.The kinetics anal ysis of DEHP degradation by strain R L-JC02 in soil demonstrated that the process fitted with the modified Gompertz model.Meanwhile,the cell concentration monitoring of strain RL-JC02 in soil with absolute quantification pol ymerase chain reaction(q PCR)suggested that strain RL-JC02 survived well during the bioremediation.This study will provide a robust degrader for the bioremediation of PAEs-contaminated sites and facilitate our knowledge of DEHP biodegradation in red soil.