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

This study was conducted to investigate the biodegradation of di-(2-ethylhexyl) phthalate (DEHP) by Burkholderia pyrrocinia B1213. The results showed that DEHP at concentration of 500 mg/L in a mineral salt medium containing 1.0% yeast extract can be almost completely degraded (98.05%) by strain B1213. The optimal condition for DEHP degradation was pH 7.0, temperature 30 °C. Moreover, B1213 shows better degradation effect on long-chain PAEs, such as DEHP, which provides a great potential for its use in bioremediation of soils contaminated with PAEs. The kinetic studies showed that DEHP depletion curves fit well to the modified Gompertz model. The mono(2-ethylhexyl) phthalate (MEHP), mono-dibutyl phthalate (MBP), phthalic acid (PA) and 4-oxo-hexanoic acid were identified as the metabolites of DEHP by HPLC-ESI-QTOFMS. The detection of MBP and 4-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 esterases, which is then converted to MBP through β-oxidation. Then MBP is degraded to PA by esterases, which is then converted to protocatechuate (PCA) under aerobic conditions rapidly. PCA is ultimately cleaved to generate CO₂ and H₂O via 4-oxo-hexanoic acid.