Mechanisms of biodegradation of dibenzoate plasticizers

• Published in: Chemosphere (Oxford) 2009-09, Vol.77 (2), p.258-263
• Main Authors: Kermanshahi pour, Azadeh, Cooper, David G., Mamer, Orval A., Maric, Milan, Nicell, Jim A.
• Format: Article
• Language: English
• Subjects: 1,6-Hexanediol dibenzoate; Air. Soil. Water. Waste. Feeding; Alcohols; Alkanes - chemistry; Alkanes - metabolism; Animal, plant and microbial ecology; Applied ecology; Applied sciences; Benzoates - chemistry; Benzoates - metabolism; Benzoic acid; Biodegradation; Biodegradation, Environmental; Biological and medical sciences; Degradation; Ecotoxicology, biological effects of pollution; Environment. Living conditions; Esters; Ethylene Glycols - chemistry; Ethylene Glycols - metabolism; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Gas Chromatography-Mass Spectrometry; Glycols; Green Chemistry Technology; Medical sciences; Metabolites; Plasticizers; Plasticizers - chemistry; Plasticizers - metabolism; Pollution; Public health. Hygiene; Public health. Hygiene-occupational medicine; Rhodococcus - metabolism; Rhodococcus rhodochrous
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2009.06.048

Biodegradation mechanisms were elucidated for three dibenzoate plasticizers: diethylene glycol dibenzoate (D(EG)DB), dipropylene glycol dibenzoate (D(PG)DB), both of which are commercially available, and 1,6-hexanediol dibenzoate, a potential green plasticizer. Degradation studies were done using Rhodococcus rhodochrous in the presence of pure alkanes as a co-substrate. As expected, the first degradation step for all of these systems was the hydrolysis of one ester bond with the release of benzoic acid and a monoester. Subsequent biodegradation of the monobenzoates of diethylene glycol (D(EG)MB) and dipropylene glycol (D(PG)MB) was very slow, leading to significant accumulation of these monoesters. In contrast, 1,6-hexanediol monobenzoate was quickly degraded and characterization of the metabolites indicated that the biodegradation proceeded by way of the oxidation of the alcohol group to generate 6-(benzoyloxy) hexanoic acid followed by β-oxidation steps. This pathway was blocked for D(EG)MB and D(PG)MB by the presence of an ether function. The use of a pure hydrocarbon as a co-substrate resulted in the formation of another class of metabolites; namely the esters of the alcohols formed by the oxidation of the alkanes and the benzoic acid released by hydrolysis of the original diesters. These metabolites were biodegraded without the accumulation of any intermediates.