Brominated organic compounds are an important group of pollutants worldwide. Many are known to be toxic, and recalcitrant to degradation. In order to find out whether these compounds are biodegraded in the environment we tested the application of multi-dimensional compound-specific isotope analysis (CSIA) combining carbon (13C/12C) and bromine (81Br/79Br) isotopes as a diagnostic tool. Two brominated compounds were used as model compounds: Dibromoneopentyl-glycol (DBNPG) and tribromoneopentyl-alcohol (TBNPA), as they have been found in the groundwater underlying the industrial site Neot Hovav, Israel.
Aerobic biodegradation potential of DBNPG and TBNPA by indigenous bacteria of the site groundwater was shown. Both compounds were successfully biodegraded in an enriched culture from contaminated groundwater with the supplement of yeast extract. Complete debromination was observed within a few days, suggesting that bromine-containing intermediates do not accumulate in the medium. Three strains were isolated from the TBNPA consortium and identified as: Pseudomonas aeruginosa; Delftia tsuruhatensis; and Pseudomonas citronellolis. Four strains were isolated from the DBNPG consortium and identified as: Pseudomonas citronellolis; Gordonia sihwensis; Shinella zoogloeoides; and Microbacterium oxydans.
Isotopic analysis of 13C/12C during the biodegradation of TBNPA revealed significant fractionation with an enrichment factor (ɛ) of -8.9‰. Surprisingly, 81Br/79Br isotopes, showed no fractionation. This may suggest that either the debromination is not a rate-limiting step in the degradation pathway or that the fractionation that occurs is below the detection limit. This work provides the basis for the development of an isotopic fractionation based tool for assessing the biodegradation of brominated organic compounds in contaminated environments.
