Aerobic Biodegradation of Methyl tert -Butyl Ether by Aquifer Bacteria from Leaking Underground Storage Tank Sites

Abstract

The potential for aerobic methyl tert-butyl ether (MTBE) degradation was investigated with microcosms containing aquifer sediment and groundwater from four MTBE-contaminated sites characterized by oxygenlimited in situ conditions. MTBE depletion was observed for sediments from two sites (e.g., 4.5 mg/liter degraded in 15 days after a 4-day lag period), whereas no consumption of MTBE was observed for sediments from the other sites after 75 days. For sediments in which MTBE was consumed, 43 to 54% of added [U-14 C]MTBE was mineralized to 14 CO 2 . Molecular phylogenetic analyses of these sediments indicated the enrichment of species closely related to a known MTBE-degrading bacterium, strain PM1. At only one site, the presence of water-soluble gasoline components significantly inhibited MTBE degradation and led to a more pronounced accumulation of the metabolite tert-butyl alcohol. Overall, these results suggest that the effects of oxygen and water-soluble gasoline components on in situ MTBE degradation will vary from site to site and that phylogenetic analysis may be a promising predictor of MTBE biodegradation potential.The magnitude and remediation cost of methyl tert-butyl ether (MTBE) contamination in drinking water have rapidly become a national concern. It has been estimated that 250,000 of the approximately 385,000 confirmed leaking underground storage tank (LUST) releases in the United States involve MTBE (15). In California, at least 10,000 LUST sites are estimated to be contaminated with MTBE (13). Several states, including California, have set primary maximum concentration levels for MTBE at or below 20 g/liter, and at an even lower level of 12 g/liter for tert-butyl alcohol (TBA), an MTBE metabolite. The U.S. Environmental Protection Agency has listed MTBE as a possible human carcinogen, whereas TBA is a known animal carcinogen (7). MTBE appears to be more mobile and less biodegradable than BTEX compounds (benzene, toluene, ethylbenzene, and xylenes), and consequently, MTBE plumes have extended over kilometer-scale distances, as is the case at Port Hueneme, Calif., and East Patchogue, N.Y.Previous microcosm studies reported little or no biodegradation of MTBE under a variety of aerobic (11,14) and anaerobic (18,23,26) conditions. More recent microcosm (3) and column (6) studies suggest that limited intrinsic biodegradation of MTBE may occur. One research group observed MTBE mineralization activity in stream-bed sediments from both contaminated and pristine sites under aerobic conditions (4,5). Mixed cultures capable of MTBE degradation have been isolated from activated sludge (10,20). Pure bacterial cultures capable of MTBE metabolism have been reported (12,17,22), including strain PM1, which uses MTBE as a sole carbon source and electron donor (12), and propane-oxidizing strains that cometabolize MTBE (22). In microcosm and field experiments, Salanitro et al. (21) showed that oxygenation in combination with bioaugmentation with an MTBE-degrading consortium resulted in more rapid MTBE degradation, alt...

Whole-Genome Analysis of the Methyl tert -Butyl Ether-Degrading Beta-Proteobacterium Methylibium petroleiphilum PM1

“…(ϳ99% similarity to PM1, based on the 16S rRNA gene) (38,67,82). PM1-like bacteria occur naturally in a number of MTBE-contaminated aquifers in the United States (46,47,82), Mexico (21), and Europe (55,61), and their presence has been correlated with MTBE degradation activity in numerous sites (47,67,82), using real-time PCR analysis (37). These results suggest that PM1-like organisms may play a major role in MTBE biodegradation under aerobic conditions in contaminated aquifers.…”

Limitations in Mtbe Biodegradation

“…Different authors recently reported the biodegradation of MTBE by microcosms from different origins Fortin et al, 2001;Kane et al, 2001;Landmeyer et al, 2001;Park and Cowan, 1997;Salanitro et al, 1994). Moreover, the cometabolic degradation of MTBE was shown to be an important mechanism for MTBE biodegradation using microrganisms able to grow on gaseous alkanes (Hardison et al, 1997;Steffan et al, 1997;Hyman and O'Reilly, 1999;Liu et al, 2001;Hyman et al, 2000), pentane (Garnier et al, 1999), camphor (Steffan et al, 1997), ethanol (Piveteau et al, 2000) or cyclohexane (Corcho et al, 2000).…”

Biodegradation of Methyl tert -Butyl Ether and Other Fuel Oxygenates by a New Strain, Mycobacterium austroafricanum IFP 2012

“…Nevertheless, a stable aerobic mixed culture that degraded MTBE via TBA was obtained (31). MTBE biodegradation by microcosms having different origins was reported later (5,24,45 MTBE cometabolism was demonstrated by using propanegrown bacteria (35), an n-butane-grown fungus (17), camphorgrown Pseudomonas putida CAM (36), pentane-grown Pseudomonas aeruginosa (14), ETBE-grown Rhodococcus ruber IFP 2007 (20), and a cyclohexane-grown mixed culture (9). Steffan et al (36) proposed a pathway for MTBE biodegradation in which MTBE was sequentially degraded to tert-butyl formate (TBF), tert-butyl alcohol, and 2-hydroxy isobutyrate (HIBA).…”