Dual bio-degradative pathways of di-2-ethylhexyl phthalate by a novel bacterium Burkholderia sp. SP4

Burkholderia sp. SP4, isolated from agricultural soils, has a high capability of degrading di-2-ethylhexyl-phthalate (DEHP). It degrades up to 99% of DEHP (300 mg l-1) in minimal salt (MS) media within 48 h without adding additionally auxiliary carbon source. The optimal conditions for SP4 to degrade DEHP are determined to be at 35 °C and pH 6.0. Supplementation of glucose (3.0 g l-1), sodium dodecyl sulfate (SDS) (0.2%), peptone (0.5 g l-1), or non-ionic surfactant Brij 35 (0.2%, 0.5% or 1%) in MS-DEHP media increases the DEHP degradation activity. Furthermore, kinetic analyses for DEHP degradation by SP4 reveals that it is a first-order reaction, and the half-life analyses also demonstrates that SP4 has a better degradative activity compared to other previously identified microbes. By means of HPLC-ESI-QTOF-MS, the metabolic intermediates of DEHP are identified for SP4, which include mono-2-ethylhexylphthalate (MEHP), mono-butyl phthalate (MBP), phthalic acid (PA), salicylic acid (SA), and 4-oxo-hexanoic acid. The presence of SA indicates that SP4 can consume DEHP using a dual biodegradation pathway diverged from the isomeric products of benzoate. Taken together, our study identifies a resilient DEHP-degradable bacterium and characterizes a novel degradation pathway for DEHP biodegradation. We plan to build on this finding in the context of removing DEHP from various environments.