Interaction of metabolites with R. rhodochrous during the biodegradation of di-ester plasticizers

• Published in: Chemosphere (Oxford) 2006-11, Vol.65 (9), p.1510-1517
• Main Authors: Nalli, Sandro, Cooper, David G., Nicell, Jim A.
• Format: Article
• Language: English
• Subjects: 2-Ethylhexanoic acid; 2-Ethylhexanol; Adipates - metabolism; adipic acid; Alcohol Dehydrogenase - metabolism; alcohol oxidoreductases; antibacterial properties; Applied sciences; biodegradation; Biodegradation of pollutants; Biodegradation, Environmental; Biological and medical sciences; Biotechnology; DEHA; DEHP; di-ethylhexyl adipate; di-ethylhexyl phthalate; Diethylhexyl Phthalate - metabolism; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environment and pollution; Enzyme; ethanol dehydrogenase; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Global environmental pollution; Hexanols - metabolism; Industrial applications and implications. Economical aspects; metabolites; phthalates; plasticizers; Plasticizers - metabolism; Pollution; Pollution, environment geology; Rhodococcus - growth & development; Rhodococcus - metabolism; Rhodococcus rhodochrous
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2006.04.010

The commonly used plasticizers di-ethylhexyl phthalate (DEHP) and di-ethylhexyl adipate (DEHA) are known to partially degrade in the presence of soil microorganisms, such as Rhodococcus rhodochrous, releasing persistent and toxic metabolites. The metabolites adipic acid and 2-ethylhexanol were both shown to inhibit growth of the degrading microbe. 2-Ethylhexanol enhanced the activity of ethanol dehydrogenase – an enzyme involved in its metabolism – but the activity of this enzyme was inhibited by adipic acid. The metabolite usually seen in the highest concentrations – 2-ethylhexanoic acid – did not exhibit any evidence of inhibition. It was shown that the high concentration of this metabolite was due to the inability of R. rhodochrous to degrade it. Comparisons with other small carboxylic acids supported the argument that the ethyl branch was the reason for the resistance of 2-ethylhexanoic acid to degradation. The hydrophobicity of the cell surface was shown to be a factor in plasticizer degradation. The primary carbon source could be either water-soluble or hydrophobic and a hydrophobic substrate led to a cell surface that attracted the plasticizer and facilitated degradation. The most hydrophobic of the plasticizers, DEHP, was particularly sensitive to this effect.