Isolation and characterization of two aerobic bacterial strains that completely degrade ethyl tert-butyl ether (ETBE)

Abstract.

Two bacterial strains, E₁ and E₂, isolated from gasoline-polluted soil completely degraded ethyl tert-butyl ether (ETBE), as the sole source of carbon and energy, at specific rates of about 80 mg g^–1 and 58 mg g^–1 of cell protein day^–1, respectively. On the basis of morphological and phenotypic characteristics, strain E₁ was tentatively identified as Comamonas testosteroni and strain E₂ as belonging to Centre for Disease Control group A-5. The inhibitory effect of metyrapone on the degradative ability of both strains was the first evidence indicating the involvement of a soluble cytochrome P-450 in the cleavage of the ETBE ether bond. This observation was confirmed by spectrophotometric analysis of reduced cell extracts that gave, in the presence of carbon monoxide, a major absorbance peak at about 450 nm. Both strains were also able to degrade, as the sole source of carbon and energy, ETBE's major metabolic intermediates (tert-butyl alcohol and tert-butyl formate) and other gasoline oxygenates (methyl tert-butyl ether and tert-amyl methyl ether). The degradation rates varied considerably, with both strains exhibiting a preferential activity for ETBE's metabolic intermediates.