Biodegradability and biodegradation pathway of di-(2-ethylhexyl) phthalate by Burkholderia pyrrocinia B1213*

Authors: ZHANG, JINGFAN - Beijing Advanced Innovation Center For Food Nutrition And Human Health, Beijing Technology & Busine; Yadav, Madhav; LI, JINLONG - Beijing Advanced Innovation Center For Food Nutrition And Human Health, Beijing Technology & Busine

Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2019
Publication Date: 3/2/2019
Citation: Zhang, J., Yadav, M.P., Li, J. 2019. Biodegradability and biodegradation pathway of di-(2-ethylhexyl) phthalate by Burkholderia pyrrocinia B1213*. Chemosphere. 225:443-450. https://doi.org/10.1016/j.chemosphere.2019.02.194.
DOI: https://doi.org/10.1016/j.chemosphere.2019.02.194

Interpretive Summary: Phthalate esters are one of the most frequently detected organic contaminants in the environment. Because they can cause cancer and also change the genetic material (DNA) in humans, they are considered as threats to human health. Finding a bacterial stain that can degrade phthalate esters will facilitate the development of strategies to reduce these contaminating agents and clean contaminated soil and ground water. Phthalate esters occur at measurable levels in different environments worldwide. The use of agricultural plastics has increased the soil contamination by phthalate esters in rural areas. Thus the need to remove phthalate esters from the environment prompted us to study their biodegradation by the bacterium, Burkholderia pyrrocinia strain B1213. Our studies have shown that this bacterial stain can degrade phthalate with both short and long chain alkyl groups. Because this bacterial strain is very efficient at degrading phthalate, it offers a unique opportunity for treating phthalate contaminated soil or water. Such bacterial treatment of soil and waste water will improve the environment and help to protect human beings from cancer and many other diseases. This study can be of great value to US citizens, US agricultural and allied industries and farmers by providing a new method for treating contaminated soil and waste water and cleaning the environment.

Technical Abstract: This study was conducted to investigate the biodegadation of di-(2-ethylhexyl) phthalate (DEHP) by Burkholderia pyrrocinia B1213. The results showed that DEHP at a concentration of 500 mg/L in a mineral salt medium containing 1.0 % yeast extract can be almost completely degraded (98.05 %) by a bacterial strain B1213. The optimal condition found from our experiments for DEHP degradation was pH 5.0-9.0, temperature 30 degree C and rotation rate 180 rpm. The kinetic studies showed that DEHP depletion curves fit well with the modified Gompertz model. The mono(2-ethylhexyl) phthalate (MEHP), mono-dibutyl phthalate (MBP), phthalic acid (PA) and 3-oxo-hexanoic acid were identified as the metabolites of DEHP by high performance liquid chromatography/electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOFMS). The detection of MBP and 3-oxo-hexanoic acid as intermediates prompted us to propose a novel and more complete DEHP biodegradation pathway compared to the classic pathway. DEHP is first degraded to MEHP by an esterase, which is then converted to MBP through ß-oxidation. Then MBP is degraded to phthalate by an esterase, which is then cleaved to generate CO2 and H2O via 3-oxo-hexanoic acid formation. Moreover, B1213 shows better degradation effect on long-chain PAEs, such as DEPH, which provides a great potential for its use in bioremediation of soils contaminated with phthalate esters.