PM02 Remediation Techniques and Strategies
Exhibit Hall
8:00 AM - Monday
(PM015) Acetylene as a reversible inhibitor for probing mechanisms of reductive dehalogenation of chlorinated ethenes.
Sabalowsky, A1, Semprini, L1, 1 Dept. of Civil, Construction and Environmental Engineering, Oregon State University, Corvallis, OR, USA
ABSTRACT- Acetylene (C2H2) has been shown to be a reversible inhibitor of reductive dechlorination of chloroethenes by an anaerobic culture. Data suggests that the presence of C2H2 can be used to reduce or stop reductive dechlorination of chloroethenes such as tetrachloroethene (PCE), trichloroethene (TCE), cis-1,2-dichloroethene (cDCE), and vinyl chloride (VC) by an anaerobic culture confirmed to contain at least one Dehalococcoides-like species. PCE and TCE dechlorination rates were reduced in the presence of C2H2. Upon removal of C2H2, dechlorination resumed, but at a slower rate than cultures not exposed to C2H2. The reduction in rate after C2H2 removal was greater than could be explained by lack of growth, indicating that binding at high C2H2 aqueous concentrations (>200 uM) may not be fully reversible. The presence of TCE at similar molar ratios to C2H2 showed some degree of protection from short-term irreversible inhibition compared to the presence of C2H2 alone, indicating C2H2 and chloroethenes may be competing for the same active enzyme site(s). Simple modeling approximations suggest the mode of inhibition is competitive. Current studies are attempting to verify the mode of inhibition, define the inhibition constant for the dechlorination reactions and probe the effects of C2H2 exposure in the absence of chloroethenes. The similarity in the inhibition coefficient, Ki, estimated for PCE and TCE dechlorination by the culture provides evidence that the same enzyme may be responsible for both reactions, demonstrating that a reversible inhibitor, such as C2H2, may be a useful tool for identifying the number of enzymes responsible for full dechlorination of PCE or TCE to ethene.
Key words: inhibition, dehalogenation, acetylene, chloroethene