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Transformation of short-chain chlorinated paraffins by the bacterial haloalkane dehalogenase LinB – Formation of mono- and di-hydroxylated metabolites.

Authors :
Knobloch, Marco C.
Schinkel, Lena
Schilling, Iris
Kohler, Hans-Peter E.
Lienemann, Peter
Bleiner, Davide
Heeb, Norbert V.
Source :
Chemosphere. Jan2021, Vol. 262, pN.PAG-N.PAG. 1p.
Publication Year :
2021

Abstract

Short-chain chlorinated paraffins (SCCPs) are listed as persistent organic pollutants (POPs) under the Stockholm Convention. Such substances are toxic, bioaccumulating, transported over long distances and degrade slowly in the environment. Certain bacterial strains of the Sphingomonadacea family are able to degrade POPs, such as hexachlorocyclohexanes (HCHs) and hexabromocyclododecanes (HBCDs). The haloalkane dehalogenase LinB, expressed in certain Sphingomonadacea, is able to catalyze the transformation of haloalkanes to hydroxylated compounds. Therefore, LinB is a promising candidate for conversion of SCCPs. Hence, a mixture of chlorinated tridecanes was exposed in vitro to LinB, which was obtained through heterologous expression in Escherichia coli. Liquid chromatography mass spectrometry (LC-MS) was used to analyze chlorinated tridecanes and their transformation products. A chloride-enhanced soft ionization method, which favors the formation of chloride adducts [M+Cl]- without fragmentation, was applied. Mathematical deconvolution was used to distinguish interfering mass spectra of paraffinic, mono-olefinic and di-olefinic compounds. Several mono- and di-hydroxylated products including paraffinic, mono-olefinic and di-olefinic compounds were found after LinB exposure. Mono- (rt = 5.9–6.9 min) and di-hydroxylated (rt = 3.2–4.5 min) compounds were separated from starting material (rt = 7.7–8.5 min) by reversed phase LC. Chlorination degrees of chlorinated tridecanes increased during LinB-exposure from n Cl = 8.80 to 9.07, indicating a preferential transformation of lower chlorinated (Cl <9) tridecanes. Thus, LinB indeed catalyzed a dehalohydroxylation of chlorinated tridecanes, tridecenes and tridecadienes. The observed hydroxylated compounds are relevant CP transformation products whose environmental and toxicological effects should be further investigated. Image 1 • Chlorinated paraffins are transformed by the enzyme LinB. • Mono- and di-hydroxylated transformation products could be identified. • Mathematical deconvolution was used to obtain non-interfered data. • Mono- and di-hydroxylated products were separated from starting material by LC. • Preferential conversion of lower chlorinated CPs was induced by LinB. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00456535
Volume :
262
Database :
Academic Search Index
Journal :
Chemosphere
Publication Type :
Academic Journal
Accession number :
146874415
Full Text :
https://doi.org/10.1016/j.chemosphere.2020.128288