Chlorinated Solvent Cometabolism by Butane-Grown Mixed Culture

A survey of aerobic cometabolism of chlorinated aliphatic hydrocarbons by a butane-grown mixed culture was performed. The transformation of 1,1-dichloroethylene (1,1-DCE) and cis-1,2-dichloroethylene (c-DCE) required O 2 and was inhibited by butane and inactivated by acetylene, indicating that a monooxygenase enzyme was likely involved in the transformations. The initial transformation rates and the quantities of chlorinated aliphatic hydrocarbons transformed were inversely proportional to the chlorine contents within each group of chlorinated methanes, ethanes, and ethenes. Lower quantities of chloroform were transformed than chloromethane and dichloromethane, but chloroform transformation resulted in much higher cell inactivation. For the ethane group, chloroethane was most effectively transformed but caused significant cell inactivation. Di- or trichloroethanes that have all chlorines on one carbon were more effectively transformed and caused less cell inactivation than the isomers that have chlorine on both carbons. For chlorinated ethenes, 1,1-DCE was most rapidly transformed, whereas trans-1,2-dichloroethylene was not transformed. Vinyl chloride was transformed to the greatest extent, and very limited transformation of trichloroethylene was observed. The 1,1-DCE transformation caused greater cell inactivation than the transformation of the other chlorinated ethenes. Chloride release studies showed nearly complete oxidative dechlorination of chlorinated methanes and chloroethane, vinyl chloride and c-DCE (86% ∼ 100%), and incomplete dechlorination of 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, and 1,1-DCE (37% ∼ 75%) was observed.