Hydrogen and Carbon Isotope Fractionation during Aerobic Biodegradation of Benzene

The main aim of the study was to evaluate hydrogen and carbon isotope fractionation during biodegradation of benzene as a possible tool to trace the process in contaminated environments. Aerobic biodegradation of benzene by two bacterial isolates, <i>Acinetobacter</i> sp. and <i>Burkholderia</i> sp., was accompanied by significant hydrogen and carbon isotope fractionation with hydrogen isotope enrichment factors of −12.8 ± 0.7‰ and −11.2 ± 1.8‰, respectively, and average carbon isotope enrichment factors of −1.46 ± 0.06‰ and −3.53 ± 0.26‰, respectively. Inorganic carbon produced by <i>Acinetobacter</i> sp. was depleted in ¹³C by 3.6−6.2‰ as compared to the initial δ¹³C of benzene, while the produced biomass was enriched in ¹³C by 3.8‰. The secondary aim was to determine isotope ratios of benzenes from different manufacturers with regard to the use of isotopes for source differentiation. While two of the four analyzed benzenes had similar δ¹³C values, each of them had a distinct δ²H−δ¹³C pair and δ²H values spread over a range of 66.5‰. Thus, combined analyses of hydrogen and carbon isotopes may be a more promising approach to trace sources and/or biodegradation of benzene than measuring carbon isotopes only.