Effect of Chlorinated Ethenes on Smin for a Methanotrophic Mixed Culture

Abstract

The presence of chlorinated aliphatic hydrocarbons (CAHs) was found to increase the minimum methane concentration for net growth (Smin) of a methanotrophic mixed culture expressing particulate methane monooxygenase (pMMO). Without CAHs, Smin was 5 μg/L methane. Smin, however, increased to 20−25 μg/L in the presence of 0.05 mg/L 1,1-dichloroethylene (1,1-DCE), 2 mg/L trans-1,2-dichloroethylene (t-DCE), or 4 mg/L trichloroethylene (TCE). A lower maximum methane oxidation rate was required to model growth rates at these low methane concentrations, a result that was attributed to reducing energy limitation. A derived equation for possible factors by which CAHs increased Smin included reducing energy limitation, competitive inhibition, and transformation product toxicity. However, a simplified model that incorporated these effects into a single parameter was adequate to model the overall effect on growth rate and Smin.