Effects of co-substrates and inhibitors on the anaerobic O-demethylation of methyl tert-butyl ether (MTBE)

Abstract

Methyl tert-butyl ether (MTBE) contamination is widespread in aquifers near urban areas around the world. Since this synthetic fuel oxygenate is resistant to most physical methods of treating fuel-contaminated water, biodegradation may be a useful means of remediation. Currently, information on anaerobic MTBE degradation is scarce. Depletion has been observed in soil and sediment microcosms from a variety of locations and under several redox conditions, but the responsible organisms are unknown. We are studying anaerobic consortia, enriched from contaminated sediments for MTBE-utilizing microorganisms for over a decade. MTBE degradation occurred in the presence of other fuel components and was not affected by toluene, benzene, ethanol, methanol, or gasoline. Many aryl O-methyl ethers, such as syringic acid, that are O-demethylated by acetogenic bacteria, were also O-demethylated by the MTBE-utilizing enrichment cultures. The addition of these compounds as co-substrates increased the rate of MTBE degradation, offering a potentially useful method of stimulating the MTBE degradation rate in situ. Propyl iodide caused light-reversible inhibition of MTBE degradation, suggesting that the MTBE degradation process is corrinoid dependent. The anaerobic MTBE degradation process was not directly coupled to methanogenesis or sulfidogenesis and was inhibited by the bactericidal antibiotic, rifampicin. These results suggest that MTBE degradation is mediated by acetogenic bacteria.

Community characterization of anaerobic methyltert-butyl ether (MTBE)-degrading enrichment cultures

“…Previous characterization of these enrichment cultures provided strong evidence that the initial attack on MTBE was mediated by bacteria (Youngster et al , 2008). Furthermore, although carbon flow was ultimately coupled to sulfidogenesis or methanogenesis, inhibition of the terminal electron‐accepting processes did not inhibit the initial transformation of MTBE (Somsamak et al , 2005, 2006).…”

Substrate interactions between toluene and methyltert‐butyl ether (MTBE) during microbial degradation by Pseudomonas putida

“…The negative effect of toluene was also reported by Morales et al [2], who found that biodegradation of MTBE at 74 mg L 21 could not be achieved in the presence of toluene at a concentration of 87 mg L 21 . In contrast, some researchers reported that there were no effects of toluene or BTEX on MTBE degradation [3][4][5][6]. In these studies, the concentrations of toluene or BTEX were in the range of 0.5-176 mg L 21 , and these concentrations were two or three times less than those of MTBE.…”

Biodegradation of gasoline ether oxygenates

“…In some recent studies, little or no biodegradation has been observed over long periods [3,4]. In other cases, rapid anaerobic biodegradation has been observed [5].…”

“…Recent studies with these cultures have focused on the frequently noted similarities between anaerobic ether oxygenate biodegradation and corrinoid-dependent demethylations of methyl ethers catalyzed by acetogenic bacteria. Several methoxylated aromatic cosubstrates such as syringate stimulate anaerobic MTBE biodegradation and degradation of MTBE by ether-stimulated cultures is inhibited in a light-reversible process by propyl iodide, a distinctive feature of corrinoid-dependent reactions [5]. The microbial communities in several MTBE-degrading enrichment cultures have been investigated and shown to be dominated by microorganisms from several phylotypes including the Firmicutes phylum that contains acetogens known to O-demethylate aromatic ethers [10 ].…”