USE OF CYANOCOBALAMIN TO ENHANCE ANAEROBIC BIODEGRADATION OF CHLOROFORM

Biodegradation of chloroform (CF) was examined in a methanogenic enrichment culture grown on dichloromethane (DCM) as the sole organic carbon and energy source, with and without the addition of supplemental cyanocobalamin. In the absence of cyanocobalamin, the principal products of [C-14] CF biodegradation were (CO2)-C-14 and [C-14]DCM. The extent of CF reduction to DCM increased significantly when CF was biodegraded in the presence of a large amount of DCM. The addition of cyanocobalamin enhanced CF biodegradation in two ways. First, the rate of CF biodegradation increased approximately 10-fold. Second, the metallocofactor increased the extent of CF oxidation to CO2 and virtually eliminated the accumulation of DCM. These effects were not observed in autoclaved cultures supplemented with cyanocobalamin. When cyanocobalamin was added to viable cultures, as much as 10% of the [C-14]CF transformed accumulated as C-14-labeled carbon monoxide. This suggested that the oxidation of CF to CO2 proceeds via net hydrolysis to CO. CF levels as high as 2.2 mM were readily transformed, without accumulation of DCM, at cyanocobalamin to CF molar ratios of 3-5%. Although the organism or consortium responsible for CF biodegradation was not identified, prior work with DCM suggests that acetogenic bacteria are involved.