Biodegradation of Three Phthalic Acid Esters by Microorganisms from Aquatic Environment

We assessed the primary and ultimate biodegradability in aquatic environments of three phthalic acid esters (PAEs)—di-n-butyl phthalate (DBP), butyl benzyl phthalate (BBP) and di (2-ethylhexyl) phthalate (DEHP)—and phthalic acid (PA) by using microbes obtained from four river-water, three pond-water and four activated sludge samples. Though none of the tested samples had been acclimatized to PAEs, all of them showed an ability to biodegrade the PAEs and PA, suggesting the ubiquitous existence of PAE-degrading microbes in aquatic environments. The PAEs underwent rapid primary biodegradation: 40 and 10 mg · l-1 TOC of the PAEs disappeared within 2 weeks via biodegradation by activated sludge samples and by river- and pond-water samples, respectively. However, ultimate biodegradation reached only 40%-80% by activated sludge and 15%-70% by river- and pond-water samples within the 2-week experimental period, and metabolites accumulated, including monoalkyl phthalates, PA, protocatechuate and β-carboxy-cis-muconate. According to analyses of the biodegradation kinetics, the investigated PAEs can be ranked by their primary and ultimate biodegradability as DBP≥BBP>DEHP and BBP≥DBP>DEHP, respectively.