Enhanced Biodegradation of Methyl tert-butyl-ether by a Microbial Consortium

Abstract The widespread use of Methyl tert-butyl-ether(MTBE) as a gasoline additive has resulted in a higherdetection rate of MTBE in groundwater systems. There-fore, the researchers show more concern about the biore-mediation of MTBE-impacted aquifers. In this paper, aMTBE-direct-degrading bacterial consortium was enriched(named RS1) and further studied. In order to identify themicrobial community of the consortium, 17 and 12 dif-ferent single strains were isolated from nutrient mediumand MSM media (with MTBE as the sole carbon source),respectively. 16S rDNA-based phylogenetic analysisrevealed that these diverse bacteria belonged to 14 genera,in which Pseudomonas was dominant. Several strainswhich can grow with MTBE as the sole carbon and energysource were also identified, such as M1, related to MTBE-degrading Arthrobacter sp. ATCC27778. Furthermore, theappropriate addition of certain single strain in consortiumRS1 (M1:RS1 = 1:2) facilitates MTBE degradation byincreasing the quantity of efficient MTBE-degrading bac-teria. This work will provide microbial source and theo-retical fundament for further bioremediation of MTBE-contaminated aquifers, which has applied potential andenvironmental importance.IntroductionOver the past decades, methyl tert-butyl-ether (MTBE) iswidely used as an oxygenate to raise the octane number andincrease the combustion efficiency of gasoline, thusdecreasing air pollution caused by emissions from gasolineincomplete combustion [1]. As an efficient gasoline addi-tive, MTBE has many favorable characteristics includingits high octane value and solubility, low production cost,and the ability to mix with other gasoline components withany proportion [2]. However, the worldwide use of MTBEhas increased the risk of MTBE pollution in groundwater.Once released to the environment, MTBE can be trans-ported to underground or surface water resources quicklybecause of its high solubility and recalcitrance to degra-dation, and lead to unpleasant taste and odor in water. Dueto these physical and chemical properties, the occurrenceof MTBE in drinking water systems has increased world-wide over the past several years [3–6]. In 1997, Environ-mental Protection Agency in the United States listedMTBE as a potential human carcinogen, and suggested thatthe states concentrations of MTBE in the range of20–40 ppb of water or below (US EPA 1997).The widespread contamination of groundwater byMTBE has increased the concern about the bioremediationof MTBE-impacted aquifers. Though MTBE is difficult todegrade because of the presence of tert-butyl group, severalmicroorganisms that can either partially or completelydegrade MTBE have been isolated from diverse environ-ments [7]. In 1999, MTBE-degrading strain, Methylibiumpetroleiphilum PM1 [8], was isolated and its genomicsequence was presented recently [9, 10]. Other aerobicMTBE-degrading bacteria include some Betaproteobacte-ria (e.g. Aquincola tertiaricarbonis L108 or Hydrogen-ophaga flava ENV735) [11, 12], as well as Arthrobacter