Compound-Specific
Isotope Analysis as a Tool
To Characterize Biodegradation
of Ethylbenzene
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Abstract
This
study applied one- and two-dimensional compound-specific isotope
analysis (CSIA) for the elements carbon and hydrogen to assess different
means of microbial ethylbenzene activation. Cultures incubated under
nitrate-reducing conditions showed significant carbon and highly pronounced
hydrogen isotope fractionation of comparable magnitudes, leading to
nearly identical slopes in dual-isotope plots. The results imply that <i>Georgfuchsia toluolica</i> G5G6 and an enrichment culture dominated
by an <i>Azoarcus</i> species activate ethylbenzene by anaerobic
hydroxylation catalyzed by ethylbenzene dehydrogenase, similar to <i>Aromatoleum aromaticum</i> EbN1. The isotope enrichment pattern
in dual plots from two strictly anaerobic enrichment cultures differed
considerably from those for benzylic hydroxylation, indicating an
alternative anaerobic activation step, most likely fumarate addition.
Large hydrogen fractionation was quantified using a recently developed
Rayleigh-based approach considering hydrogen atoms at reactive sites.
Data from nine investigated microbial cultures clearly suggest that
two-dimensional CSIA in combination with the magnitude of hydrogen
isotope fractionation is a valuable tool to distinguish ethylbenzene
degradation and may be of practical use for monitoring natural or
technological remediation processes at field sites