Cometabolism of methyl tert-butyl ether (MTBE) with alkanes

Abstract

The release of methyl tert-butyl ether (MTBE) to the environment, mainly from damaged gasoline underground storage tanks or distribution systems spills, has provoked extended groundwater pollution. Biological treatments are, in general, a good alternative for bioremediation of polluted sites; however, MTBE elimination from environment has constituted a challenge because of its chemical structure and physicochemical properties. The combination of a stable ether link and the branched moiety hinder biodegradation. Initial studies found MTBE to be highly recalcitrant but, in the last decade, reports of its biodegradation have been published first under aerobic conditions and just recently under anaerobic conditions. Microbial MTBE degradation is characterized by bacteria having low growth rates (0.35 day -1 ) and biomass yields (average value 0.24 g biomass/g MTBE). Alternatively, cometabolism (defined as the transformation of a non-growth substrate in the obligate presence of a growth substrate), has been considered since it uncouples biodegradation of the contaminant from growth, reducing the long adaptation and propagation period. This period has been reported to be of several months in systems where it is degraded as sole carbon source. Cometabolic degradation rates are between 0.3 and 61 nmol/min/mg protein (in the same range of direct aerobic metabolism). However, a major concern in MTBE cometabolism is that the accumulation of tert-butyl alcohol (TBA) may, under certain cases, result in an incomplete site cleanup. This paper reviews in detail the implicated enzymes and field treatments for the cometabolism of MTBE degradation with alkanes as growth substrates.

Mineralization of methyl tert-butyl ether and other gasoline oxygenates by Pseudomonads using short n-alkanes as growth source

“…Cometabolism has shown to be a mechanism for removing paraffinic, aromatic and chlorinated compounds in nature (Hovarth 1972) and has been reported to be relevant for MTBE biodegradation (Nava et al 2007). Cometabolism involves the use of an additional carbon source for growth and some compounds present in gasoline have been reported for their ability to induce enzymes able to degrade MTBE.…”

Biodegradation of Methyl Tert-butyl Ether in a Bioreactor using Immobilized Methylibium petroleiphilum PM1 Cells

“…The differences between the initial concentrations of MTBE in the influent and effluent in the biodegradation process were much bigger than those in the volatilization process, indicating that the immobilized cells could biodegrade MTBE to CO 2 and H 2 O. When the influent MTBE concentration was 15 mg/L, TBA, as one of the most important intermediates (Nava et al 2007), was detected in the effluent by GC analysis. A number of small organic acids, such as formic acid and acetic acid, could also be detected by ion chromatography.…”

“…Although it was originally believed that MTBE biodegradation was hampered by the high energy requirement for attacking its ether bond, several bacterial and fungal cultures, including an aerobic one (BC-1) (Nava et al 2007), Methylobacterium mesophilicum ATCC 700107, Arthrobacter ilicis ATCC 700109, Rhodococcus sp. ATCC 700108 (Mo et al 1997), Hydrogenophaga flava ENV735, Methylibium petroleiphilum PM1, and Mycobacterium austroafricanum IFP 2012 (Nava et al 2007), have been shown to have the capability to degrade MTBE under various environmental conditions. Recent studies have demonstrated that some aerobic cultures, such as Pseudomonas putida GPo 1 (octane), Gordonia terrae (ethanol), and Mycobacterium vaccae JOB5 (propane), are able to co-metabolize MTBE (Nava et al 2007).…”

“…ATCC 700108 (Mo et al 1997), Hydrogenophaga flava ENV735, Methylibium petroleiphilum PM1, and Mycobacterium austroafricanum IFP 2012 (Nava et al 2007), have been shown to have the capability to degrade MTBE under various environmental conditions. Recent studies have demonstrated that some aerobic cultures, such as Pseudomonas putida GPo 1 (octane), Gordonia terrae (ethanol), and Mycobacterium vaccae JOB5 (propane), are able to co-metabolize MTBE (Nava et al 2007). These aerobic cultures were all growing on other organic substrates.…”

Microbial Community from MTBE-Contaminated Soil for Aerobic Biodegradation of MTBE

“…For the last 15 years, it has been added in higher concentrations (up to 15% (v/v)) to increase fuel combustion efficiency and to lower emissions of CO and other air pollutants [1]. The release of MTBE to the environment, mainly from damaged gasoline underground storage tanks or distribution systems spills, has provoked extended groundwater pollution [2]. Solubility of MTBE in water is approximately 50,000 mg/L at 25˚C and has a low organic carbon-based partitioning coefficient (K OC ) of 11 cm 3 /g resulting in minimal sorption and retardation in natural aquifer [3].…”