Enrichment and characterization of MTBE-degrading cultures under iron and sulfate reducing conditions

Abstract

The aim of this study was to enrich cultures capable of anaerobic methyl tert-butyl ether (MTBE) biodegradation and to determine their compositions using biomolecular tools. MTBE biodegradation as the sole carbon source was observed under Fe(III) and SO42–reducing conditions and with both electron acceptors present together. The estimated MTBE biodegradation rates ranged from 3.80 to 9.20 mg·L–1·d–1when Fe(III) was the sole electron acceptor, from 1.46 to 1.70 mg·L–1·d–1when Fe(III) and SO42–were present together, and from 1.13 to 1.71 mg·L–1·d–1when SO42–was the sole electron acceptor. Five to eight members were identified in the three consortia, and their characteristics were congruent with the electron acceptor conditions. A clone 99% similar to a recently described MTBE degrader, Ochrobactrum cytisi, was detected in both cultures containing Fe(III). Other 16S rRNA gene sequences detected were highly similar at the species or genus level to additional known MTBE degraders, including Pseudomonas spp. (cometabolic), Sphinogomonas, Achromobacter, and Rhodococcus. Results suggest that the buildup of intermediates and (or) the presence of sulfides had an inhibitory effect on biodegradation. Anaerobic MTBE biodegradation remains poorly understood, and degrading strains still have not been identified to date. This work represents the first detailed 16S rRNA gene profiling of highly enriched iron- and sulfate-reducing MTBE-degrading consortia. These results may provide useful biomarkers to support current efforts for confirming anaerobic MTBE biodegradation in the field.