Degradation of Hydrohalocarbons and Brominated Compounds by Methane- and Propane-Oxidizing Bacteria

Abstract

Concern over the use of chemicals that potentially contribute to ozone depletion and the greenhouse effect has led to a ban on chlorofluorocarbons (CFCs) and potential limitations on the use of methyl bromide and other brominated fumigants. The objective of this work was to test naturally occurring aerobic microorganisms for the ability to degrade brominated fumigants and the hydrohalocarbons that have been developed to replace CFCs. The bacterial strains used in this study degraded a significant percentage of the hydrohalocarbons and brominated fumigants tested, which were present at high substrate levels. Degradation was often rapid and complete. Ion chromatog raphy results indicated the stoichiometric release of halogens for several of the compounds tested. Many of the compounds were readily biodegradable at high concentrations and were metabolized by all of the strains tested, while others were more recalcitrant. The presence of these microorganisms in the environment may represent a natural sink for some of these compounds; however, the high substrate and bacterial concentrations used in this study were chosen for bioreactor development. Information about the biodegradability of these compounds may make it easier to choose the most ecologically safe CFC replacements and fumigants.