ABSTRACT
The biodegradation of plasticizers has been previously shown to result in the accumulation of metabolites that are more toxic than the initial compound. The present work shows that the pattern of degradation of di-2-ethylhexyl adipate by Bacillus subtilis can be significantly altered by the presence of biosurfactants, such as surfactin, or synthetic surfactants, such as Pluronic L122. In particular, this work confirms that the monoester, mono-2-ethylhexyl adipate, is a metabolite in the breakdown of the plasticizer. This metabolite was proposed but not observed in earlier studies. Toxicity measurements showed it to be significantly more toxic than the plasticizer. Thus, the effect of the surfactants was to significantly increase the accumulation of one or both of the two most toxic metabolites; i.e., the monoester and 2-ethylhexanol. It was proposed that the most likely cause of the effect of the surfactants was the sequestering of these two metabolites into mixed micelles, resulting in their reduced availability for further degradation.
Subject(s)
Bacillus subtilis/metabolism , Plasticizers/chemistry , Plasticizers/metabolism , Surface-Active Agents/metabolism , Adipates/chemistry , Adipates/isolation & purification , Adipates/toxicity , Bacillus subtilis/drug effects , Bacillus subtilis/growth & development , Biodegradation, Environmental , Filtration , Hexanols/analysis , Hexanols/isolation & purification , Hexanols/toxicity , Lipopeptides , Micelles , Microbial Sensitivity Tests , Peptides, Cyclic/metabolismABSTRACT
2-Ethylhexanol has been identified as a volatile organic compound (VOC) that contributes to the deterioration of indoor air quality. Plasticizers are common components of dust and building materials and are shown to be degraded by a variety of bacteria and fungi to produce 2-ethylhexanol and other metabolites. Of these, the 2-ethylhexanol has significant volatility and was observed in appreciable quantities. The degree to which 2-ethylhexanol is observed as a VOC in air samples would be limited by the fact that many of the microorganisms that are capable of producing this compound are also able to oxidize it to 2-ethylhexanoic acid, which is much less volatile. It is argued that an abiotic degradation mechanism of plasticizers that results in the generation of 2-ethylhexanol is unlikely and, if this did occur, other metabolites should have been observed. Thus, the microbial degradation of plasticizers is the most likely source of 2-ethylhexanol in indoor air.
