Ability of oxygenases in Rhodococcus rhodochrous to degrade methyl tert-butyl ether

Methyl tert-Butyl Ether (MTBE) is widely used in gasoline to reduce ozone and carbon monoxide emissions. MTBE now contaminates 10% of the water in areas where it is used. MTBE is very water-soluble and highly recalcitrant, and was once considered non-biodegradable. One common bacterium used in other bioremediation studies is Rhodococcus rhodochrous. This organism exhibits enzymatic flexibility and can degrade a wide variety of VOCs. This study was designed to determine if R. rhodochrous grown on propane, n-butane, or iso-butane as the sole carbon and energy source could degrade MTBE. This study showed that cells grown on each of the above hydrocarbons could degrade MTBE. Tert-butyl alcohol (TBA) was produced and subsequently degraded by the cells as well. The addition of chloramphenicol to hydrocarbon-grown cells as an inhibitor of protein synthesis failed to inhibit MTBE degradation in propane and iso-butane-grown cells, indicating MTBE is degraded via cometabolism. Cells grown on propane and iso-butane could also degrade MTBE after the addition of potassium cyanide indicating that the enzyme responsible for MTBE degradation is not a monooxygenase. Comparisons of degradation rates along with RQ values show that cells grown on propane and iso-butane utilize an intermolecular dioxygenase, while cells grown on n-butane use a monooxygenase to degrade MTBE.