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
    
 
    
        e-ISSN
        1520-5851
    
 
    
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	    Volume: 53,  
	    Issue: 3,  
	    Pages: 1197-1205 
	    Article Number: ,  
	    Supplement: ,  
	
    
 
    
        
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            ACS
        
 
        
            Publishing Place
            Washington, DC
        
 
	
        
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        Reviewing status
        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