Accelerated biotransformation of carbon tetrachloride and chloroform by sulfate-reducing enrichment cultures

Abstract

The biotransformation of carbon tetrachloride (CT) and chloroform (CF) was examined with lactate- and acetate-grown sulfate-reducing enrichment cultures. Both cultures transformed CT, with approximately 50% reductively dechlorinated to CF and up to 10% to dichloromethane (DCM). Addition of cyanocobalamin increased the rate of CT transformation more than 100-fold. The principal product from [{sup 14}C]CT with cyanocobalamin added was carbon disulfide (CS{sub 2}); less than 3% was reduced to CF plus DCM. Autoclaved cultures that received cyanocobalamin were only one third as fast as their live counterparts, but produced similar amounts of CS{sub 2}. With CF, addition of cyanocobalamin to acetate- and lactate-grown cultures also increased the rate of transformation more than 100-fold. DCM was the principal transformation product until CF additions reached 270 mg/L, at which point almost no increase in DCM was observed. Thus, low levels of cyanocobalamin substantially accelerated the rate of CT and CF transformation and altered the distribution of products formed.