Small 13C/12C Fractionation Contrasts with Large Enantiomer Fractionation in Aerobic Biodegradation of Phenoxy Acids
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- 作者：Shiran Qiu ; Erkin G枚zdereliler ; Philip Weyrauch ; Eva C. Magana Lopez ; Hans-Peter E. Kohler ; Sebastian R. S酶rensen ; Rainer U. Meckenstock ; Martin Elsner
- 刊名：Environmental Science & Technology
- 出版年：2014
- 出版时间：May 20, 2014
- 年：2014
- 卷：48
- 期：10
- 页码：5501-5511
- 全文大小：587K
- 年卷期：v.48,no.10(May 20, 2014)
- ISSN：1520-5851
文摘
Phenoxy acid herbicides are important groundwater contaminants. Stable isotope analysis and enantiomer analysis are well-recognized approaches for assessing in situ biodegradation in the field. In an aerobic degradation survey with six phenoxyacetic acid and three phenoxypropionic acid-degrading bacteria we measured (a) enantiomer-specific carbon isotope fractionation of MCPP ((R,S)-2-(4-chloro-2-methylphenoxy)-propionic acid), DCPP ((R,S)-2-(2,4-dichlorophenoxy)-propionic acid), and 4-CPP ((R,S)-2-(4-chlorophenoxy)-propionic acid); (b) compound-specific isotope fractionation of MCPA (4-chloro-2-methylphenoxyacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid); and (c) enantiomer fractionation of MCPP, DCPP, and 4-CPP. Insignificant or very slight (蔚 = 鈭?.3鈥?to 鈭?.0鈥? carbon isotope fractionation was observed. Equally small values in an RdpA enzyme assay (蔚ea = 鈭?.0 卤 0.1鈥? and even smaller fractionation in whole cell experiments of the host organism Sphingobium herbicidovorans MH (蔚wc = 鈭?.3 卤 0.1鈥? suggest that (i) enzyme-associated isotope effects were already small, yet (ii) further masked by active transport through the cell membrane. In contrast, enantiomer fractionation in MCPP, DCPP, and 4-CPP was pronounced, with enantioselectivities (ES) of 鈭?.65 to 鈭?.98 with Sphingomonas sp. PM2, 鈭?.63 to 鈭?.89 with Sphingobium herbicidovorans MH, and 0.74 to 0.97 with Delftia acidovorans MC1. To detect aerobic biodegradation of phenoxypropionic acids in the field, enantiomer fractionation seems, therefore, a stronger indicator than carbon isotope fractionation.