Abstract

Enhanced Biotransformation of Carbon Tetrachloride by Acetobacterium woodii upon Addition of Hydroxocobalamin and Fructose Syed A. Hashsham 1 , * and David L. Freedman 2 Center for Microbial Ecology and Department of Civil and Environmental Engineering, Michigan State University, E. Lansing, Michigan 48824, 1 and Department of Environmental Engineering and Science, Clemson University, Clemson, South Carolina 29631 2 ABSTRACT The objective of this study was to evaluate the effect of hydroxocobalamin (OH-Cbl) on transformation of high concentrations of carbon tetrachloride (CT) by Acetobacterium woodii (ATCC 29683). Complete transformation of 470 μM (72 mg/liter (aqueous)) CT was achieved by A. woodii within 2.5 days, when 10 μM OH-Cbl was added along with 25.2 mM fructose. This was approximately 30 times faster than A. woodii cultures (live or autoclaved) and medium that did not receive OH-Cbl and 5 times faster than those controls that did receive OH-Cbl, but either live A. woodii or fructose was missing. CT transformation in treatments with only OH-Cbl was indicative of the important contribution of nonenzymatic reactions. Besides increasing the rate of CT transformation, addition of fructose and OH-Cbl to live cultures increased the percentage of ( 14 C)CT transformed to 14 CO 2 (up to 31%) and 14 C-labeled soluble materials (principally l -lactate and acetate), while decreasing the percentage of CT reduced to chloroform and abiotically transformed to carbon disulfide. 14 CS 2 represented more than 35% of the ( 14 C)CT in the presence of reduced medium and OH-Cbl. Conversion of CT to CO was a predominant pathway in formation of CO 2 in the presence of live cells and added fructose and OH-Cbl. These results indicate that the rate and distribution of products during cometabolic transformation of CT by A. woodii can be improved by the addition of fructose and OH-Cbl.