Biodegradability of di(2-ethylhexyl) phthalate by Pseudomonas fluorescens FS1

Di(2-ethylhexyl)phthalate (DEHP), one of high-molecular weight phthalate esters (PAEs), is used in the manufacturing of polyvinylchloride (PVC) resins, polyvinyl acetate, cellulosics, and polyurethanes, and contributes to environmental pollution. In this article, the characteristics of DEHP biodegradation by an effective degradation bacterium, Pseudomonas fluorescens FS1 that isolated from the activated sludge at a petrochemical factory, was capable of using phthalate esters as the sole carbon and energy source, were investigated. Experimental results showed that the biodegradation of DEHP by P. fluorescens FS1 could be described by the first-order reaction model, which could be expressed as: lnC = -0.0688t + A, and the half-life of DEHP biodegradation was 10.07 d when the initial concentrations of DEHP were less than 50 mg L-1. The inhibition effects of DEHP as a substrate had become predominant above the concentration of 50 mg L-1. The PAEs-degrading enzyme of P. fluorescens FS1, mainly located in the soluble part and the particle of cytoplasm, was an intracellular enzyme. The metabolites of DEHP degradation by P. fluorescens FS1, which monoester, phthalic acid, benzonic acid, phenol, were extracted using dichloromethane at different time intervals and identified by the GC-MS. The tentative pathway proposed for degradation of DEHP by P. fluorescens FS1 under aerobic condition is monoester in the beginning, further enzymatic degradation of the monoester produces phthalic acid, benzonic acid, phenol and finally CO2 and H2O.