THWRC Awarded Proposal 515TAM0044H

Project Number:       515TAM0044H

Title:                           Role of Facultative Methantrophs in Pollutant Degradation

Lead PI:                     Kung-Hui Chu

Awarded Amount:    $48,000


The goal of this study is to better understand the ability of facultative methanotrophs to degrade various pollutants under different culture and environmental conditions.  Facultative methanotrophs are a new group of methane-oxidizing bacteria capable of growth on multi-carbon substrates like acetate, ethanol or propane ― a unique feature that dispelled our previous believes that methanotrophs can only grow on one-carbon substrates like methane and methanol.  Most interestingly, during the growth on these alternative substrates, some of these facultative methanotrophs constitutively express methane monooxygenase (pMMO), an enzyme expressed by the typical methanotrophs for oxidizing methane to methanol.  pMMO is also known for its ability to cometabolize a wide range of environmental pollutants, including chlorinated solvents.  Furthermore, some facultative methanotrohps can only express soluble methane monooxygenase (sMMO) which is known for its broad substrate range including chlorinated solvents and other emerging contaminants like 1,4-dioxane.  Most known facultative methanotrophs are acid tolerant.  Dechlorination of selected chlorinated solvents by a facultative methanotrophic strain expressing constitutive pMMO has been recently reported, suggesting the potential role of facultative methanotrophs in natural attenuation.  Nevertheless, the degradation ability of many other facultative methanotrophs remains unclear and waits for discover.  The ability of growth on multi-carbon while expressing MMO potentially offers a new approach for methanotrophic- bioremediation for contaminated aquifers. We recently isolate several acid-tolerant facultative methanotrophs.  To this end, the objectives of this study are to (i) examine the degradation ability of our isolates and available facultative methanotrophic strains for chlorinated solvents, 1,4-dioxane and N-nitrosodimethylamine under different growth and pH conditions, and (ii) evaluate factors that  evaluate factors and conditions affecting pollution degradation by facultative methanotrophs.  The results obtained from this project are expected to yield the fundamental knowledge on their degradation ability for the tested contaminants, and factors for shaping favorable growth conditions for facultative methanotrophs at sites, and such lay the groundwork for possible enhanced attenuation or active bioremediation technologies.