Kinetics of Methyl t -Butyl Ether Cometabolism at Low Concentrations by Pure Cultures of Butane-Degrading Bacteria

Abstract

Butane-oxidizing Arthrobacter (ATCC 27778) bacteria were shown to degrade low concentrations of methyl t-butyl ether (MTBE; range, 100 to 800 g/liter) with an apparent half-saturation concentration (K s ) of 2.14 mg/liter and a maximum substrate utilization rate (k c ) of 0.43 mg/mg of total suspended solids per day. Arthrobacter bacteria demonstrated MTBE degradation activity when grown on butane but not when grown on glucose, butanol, or tryptose phosphate broth. The presence of butane, tert-butyl alcohol, or acetylene had a negative impact on the MTBE degradation rate. Neither Methylosinus trichosporium OB3b nor Streptomyces griseus was able to cometabolize MTBE.The prevalent use of methyl t-butyl ether (MTBE) for gasoline oxygenation has led to its introduction into groundwater from spills and leaky underground storage tanks. MTBE is poorly adsorbed, chemically and biologically stable, and very soluble in water, making it very mobile and persistent in the environment. The U.S. Environmental Protection Agency has recently proposed scaling back the use of MTBE in gasoline in light of the increasing frequency with which MTBE is found as a groundwater contaminant nationwide (16; http://www.epa.gov /swerust1/mtbe/browner.pdf). Concentrations of MTBE in groundwater have been reported to range from 0.5 g/liter to Ͼ10 mg/liter. At least 20 states have established MTBE groundwater cleanup levels ranging from 20 to 400 g/liter for groundwater for potable use (http://www.epa.gov/OUST/mtbe /sumtable.htm). The U.S. Environmental Protection Agency has established a health advisory level of 20 to 40 g/liter for MTBE in drinking water (19).Efforts to develop bioremediation processes to help combat MTBE contamination of groundwater have been hampered by the recalcitrance of MTBE. The highly branched nature of MTBE resists most bacterial enzymatic attacks. Only a few pure and mixed bacterial cultures that are able to biodegrade MTBE have been identified (4,6,7,8,17).One potential MTBE biodegradation pathway involves the demethylation of MTBE to form tert-butyl alcohol (TBA) and formaldehyde (11, 17; K. L. Hurt, J. T. Wilson, and J. S. Cho, 5th Int. In Situ On-Site Bioremediation Symp., 1999), although the formation of tert-butyl formate from MTBE has also been observed (8). tert-Butyl formate is then hydrolyzed into TBA. In general, TBA is the first stable metabolite of MTBE, regardless of the type of bacterial cultures used. Hyman et al. (8) presented evidence that TBA is degraded by the same enzyme that degrades MTBE, although a soil microcosm was identified that was able to biodegrade TBA but not MTBE (M. J. Zenker, R. C. Borden, and M. A. Barlaz, 5th Int. In Situ On-Site Bioremediation Symp., 1999). TBA is biodegraded at a slower rate than MTBE (8, 17); thus, it tends to build up over time. If TBA is indeed degraded by the same enzyme that degrades MTBE, then the accumulation of TBA can have a detrimental effect on the MTBE biodegradation rate as a result of enzyme competition. Consequently, the effects of TBA on MTBE b...

Diversity of Alkane Hydroxylase Systems in the Environment

“…A new application area of alkane hydroxylases is the cometabolic degradation of TCE, MTBE, and related compounds by bacteria able to grow on short-chain alkanes (typically propane to pentane) [8,[116][117][118][119][120]. The propane and TCE degrading strain P. butanovora was shown to contain butane monooxygenase genes that were closely related to sMMO [33].…”

Genes Involved in the Degradation of Ether Fuels by Bacteria of the Mycobacterium/Rhodococcus Group

“…In recent years, however, several studies have shown that bacterial [1][2][3][4][5][6][7] and fungal [8] isolates are capable of breaking the ether bond of ether fuels, generating tert-butyl alcool (TBA) in the process. TBA can then be further metabolized, either by the same microorganism [2,[5][6][7] or by other microorganisms living in the same natural or artificial consortium [9][10][11].…”

Microbiological degradation of pentane by immobilized cells of Arthrobacter sp.

“…(Liu et al 2001), Pseudomonas citronellonis (Bhattacharya et al 2003), Pseudomonas oleovorans (Witholt et al 1990), Pseudomonas aeruginosa (Belhaj et al 2002), Hormoconis resinae (Solana & Gaylarde 1995), Aspergillus niger (Volke-Sepulveda et al 2003) and three bacterial enriched consortia isolated from polluted areas as described by Okeke & Frankeberger (2003).…”