Rate-limiting mass transfer in micropollutant degradation revealed by isotope fractionation in chemostat.
Environ. Sci. Technol. 53, 1197-1205 (2019)
Biodegradation of persistent micropollutants like pesticides often slows down at low concentrations (mu g/L) in the environment. Mass transfer limitations or physiological adaptation are debated to be responsible. Although promising, evidence from compound-specific isotope fractionation analysis (CSIA) remains unexplored for bacteria adapted to this low concentration regime. We accomplished CSIA for degradation of a persistent pesticide, atrazine, during cultivation of Arthrobacter aurescens TCl in chemostat under four different dilution rates leading to 82, 62, 45, and 32 mu g/L residual atrazine concentrations. Isotope analysis of atrazine in chemostat experiments with whole cells revealed a drastic decrease in isotope fractionation with declining residual substrate concentration from epsilon(C) = -5.36 +/- 0.20 parts per thousand at 82 mu g/L to epsilon(C) = -2.32 +/- 0.28 parts per thousand at 32 mu g/L. At 82 mu g/L epsilon(C) represented the full isotope effect of the enzyme reaction. At lower residual concentrations smaller epsilon(C) indicated that this isotope effect was masked indicating that mass transfer across the cell membrane became rate-limiting. This onset of mass transfer limitation appeared in a narrow concentration range corresponding to about 0.7 mu M assimilable carbon. Concomitant changes in cell morphology highlight the opportunity to study the role of this onset of mass transfer limitation on the physiological level in cells adapted to low concentrations.
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Publication type
Article: Journal article
Document type
Scientific Article
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Keywords
Atrazine Catabolism Genes; Bioavailability Restrictions; Carbon; Growth; Biodegradation; Transformation; Limitation; Bacteria; Sulfate; Energy
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Language
english
Publication Year
2019
Prepublished in Year
2018
HGF-reported in Year
2018
ISSN (print) / ISBN
0013-936X
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1520-5851
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Volume: 53,
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Pages: 1197-1205
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ACS
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Washington, DC
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Peer reviewed
POF-Topic(s)
20403 - Sustainable Water Management
Research field(s)
Environmental Sciences
PSP Element(s)
G-504390-001
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Erfassungsdatum
2019-01-10