title: Carbon isotopic fractionation during biodegradation of phthalate esters in anoxic condition.
abstract: Here we evaluate the quantitative relationship between carbon isotopic fractionation and anoxic biodegradation of phthalate esters (PAEs), a kind of endocrine disruptors. The stable carbon isotope delta values (δ(13)C) of 4 PAEs, i.e. di-methyl phthalate (DMP), di-ethyl phthalate (DEP), di-n-butyl phthalate (DBP), and di-iso-butyl phthalate (DiBP), were analyzed during biodegradation by a pure bacteria strain isolated from the shallow aquifer sediment in anoxic condition. Results showed that the carbon isotopic fractionation in the initial degradation of PAEs was well-described by the Rayleigh equation model with R(2) from 0.8885 to 0.9821. The carbon isotopic fractionation (ε) for DMP and DEP were -4.6±0.4‰ and -2.9±0.1‰, respectively, while DBP and DiBP showed limited isotopic fractionation. A linear relationship between ε values and the total carbon atoms present in straight-carbon-chain PAE molecules with R(2) of 0.9918. The apparent kinetic isotope effects (AKIEs) were calculated for proposed 4 initial transformation pathways of PAEs. The high carbon AKIEs of 1.048 and 1.036 were obtained for single enzymatic hydrolysis of DMP and DEP, respectively, and fell in the expected KIE range of 1.03-1.09. However, the intrinsic carbon isotope effects for enzymatic hydrolysis of DBP and DiBP might be masked.
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China; Department of Environmental Sciences and Engineering, School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China. Electronic address: zliuhui@hotmail.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan 430074, PR China; Department of Environmental Sciences and Engineering, School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Wu
authors.affiliation: Department of Geography, Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Xianyu
authors.initials: X
authors.lastname: Huang
authors.affiliation: UC Davis Stable Isotope Facility, Department of Plant Sciences, One Shields Avenue, Davis, CA 95616, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Yarnes
authors.affiliation: Department of Environmental Sciences and Engineering, School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Minjing
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Environmental Sciences and Engineering, School of Environmental Studies, China University of Geosciences, Wuhan 430074, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Tong
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002244:Carbon; D002247:Carbon Isotopes / Q000032:analysis; D005591:Chemical Fractionation; D002851:Chromatography, High Pressure Liquid; D052244:Endocrine Disruptors / Q000032:analysis*; D004952:Esters; D019015:Geologic Sediments / Q000382:microbiology; D007700:Kinetics; D008962:Models, Theoretical; D010795:Phthalic Acids / Q000032:analysis*
chemical_list: D002247:Carbon Isotopes; D052244:Endocrine Disruptors; D004952:Esters; D010795:Phthalic Acids; C032279:phthalic acid; D002244:Carbon
keywords: Anoxic conditions; Biodegradation; Carbon isotope; Isotopic fractionation; Phthalate acid esters (PAEs)