US EPA

1941264 

Journal Article 

Combined carbon and hydrogen isotope fractionation investigations for elucidating benzene biodegradation pathways 

Fischer, A; Herklotz, I; Herrmann, S; Thullner, M; Weelink, SA; Stams, AJ; Schlömann, M; Richnow, HH; Vogt, C 

2008 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

42 

12 

4356-4363 

English 

18605555 

10.1021/es702468f 

WOS:000256705600022 

https://www.scopus.com/inward/record.uri?eid=2-s2.0-45249114661&doi=10.1021%2fes702468f&partnerID=40&md5=ce5dee99c15acdd674ee518bb26b1f64
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Recently, combined carbon and hydrogen isotope fractionation investigations have emerged as a powerful tool for the characterization of reaction mechanisms relevant for the removal of organic pollutants. Here, we applied this approach in order to differentiate benzene biodegradation pathways under oxic and anoxic conditions in laboratory experiments. Carbon and hydrogen isotope fractionation of benzene was studied with four different aerobic strains using a monooxygenase or a dioxygenase for the initial benzene attack, a facultative anaerobic chlorate-reducing strain as well as a sulfate-reducing mixed culture. Carbon and hydrogen enrichment factors (epsilon(C), epsilon(H)) varied for the specific pathways and degradation conditions, respectively, so that from the individual enrichment factors only limited information could be obtained for the identification of benzene biodegradation pathways. However, using the slope derived from hydrogen vs carbon isotope discriminations or the ratio of hydrogen to carbon enrichment factors (lambda = deltaH/ deltaC approximately epsilon(H)/epsilon(C)), benzene degradation mechanisms could be distinguished. Although experimentally determined lambda values partially overlapped, ranges could be determined for different benzene biodegradation pathways. Specific lambda values were < 2 for dihydroxylation, between 7 and 9 for monohydroxylation, and > 17 for anaerobic degradation. Moreover, variations in lambda values suggest that more than one reaction mechanism exists for monohydroxylation as well as for anaerobic benzene degradation under nitrate-reducing, sulfate-reducing, or methanogenic conditions. Our results show that the combined carbon and hydrogen isotope fractionation approach has potential to elucidate biodegradation pathways of pollutants in field and laboratory microcosm studies. 

Microbiology Abstracts A: Industrial & Applied Microbiology; Biotechnology and Bioengineering Abstracts; Pollution Abstracts; Biodegradation; Dioxygenase; Laboratory testing; Fractionation; Mixed culture; Hydrogen; hydrogen isotopes; microcosms; monooxygenase; Benzene; Reaction mechanisms; Pollutants; Pollutant removal; Isotopes; carbon isotopes; A 01320:Microbial Degradation; W 30950:Waste Treatment & Pollution Clean-up; P 9000:ENVIRONMENTAL ACTION