Biodegradation of methyl tertiary-butyl ether (MTBE) and other fuel oxygenates.

Methyl tertiary-butyl ether (MTBE) has been added to gasoline in the U.S. for the last decade in order to meet the mandates of the 1990 Clean Air Act. This law decreed that gasoline sold in many locations must contain oxygenates to improve combustion and minimize air pollution. Unfortunately, this widespread use has led to the contamination of some soils and aquifers, and remediation is now required. Bioremediation has proven to be an environmentally responsible and cost-effective approach to remediating petroleum spills; this article reviews the potential that bioremediation may also be appropriate for remediating MTBE contamination. There is now good evidence that MTBE can be degraded by bacteria and fungi under aerobic conditions, and promising indications that the process also occurs under methanogenic and ferric iron-reducing conditions. Yet, apparently it is not a widespread phenomenon. The challenge is to find effective bioremediation strategies that maximize this biodegradation so that it can be used reliably in cleaning contaminated sites. Both simple biostimulation and more complex bioaugmentation protocols are being developed to meet this pressing need.