Commingled contamination of 1,4-dioxane (dioxane) and chlorinated volatile organic compounds (cVOCs) represents a widespread remediation challenge given their disparate physiochemical properties and inhibitory effects on associated degrading enzymes. Particularly, dioxane degradation by a number of previous dioxane degrading bacteria can be significantly inhibited by the presence of cVOCs. Our lab isolated a novel Gram-negative bacterial strain DD4 that can co-oxidize dioxane and a number of cVOCs of high toxicity (e.g., 1,1-DCE, cis-1,2-DCE, 1,2-DCA, and VC) when grown with propane. In this study, we characterized the degradation kinetics of aerobic cometabolism of dioxane and cVOCs degradable by DD4 by fitting with the Michaelis-Menten equation. Release of free chlorides was observed during cometabolism, indicating the occurrence of dechlorination by DD4. We further assessed the inhibition of cVOCs on dioxane cometabolism and found the inhibitory effects in the following order: 1,1-DCE &gt; TCE &gt; 1,1,1-TCA. Though 1,1-DCE exerted a relatively high inhibition, DD4 is capable of alleviating and overcoming such detriment by enzymatic decomposition of this inhibitor and quenching toxic metabolites with secreted bioactive molecules. Additionally, impact of environmental factors (e.g., temperature, pH, and salinity) was evaluated on the growth and activity of DD4. DD4 can survive in relatively cold environment at temperature as low as 10 °C, and tolerate the salinity as high as 3% (as NaCl, w/v%). Overall, our kinetic and physiological studies of DD4 indicate it is a robust and superior inoculum candidate for in situ bioaugmentation or ex situ bioreactor treatment to mitigate commingled contamination of dioxane and cVOCs at a variety of field environments.

Kinetics and inhibition of cometabolic oxidation of 1,4-dioxane and Co-contaminants by a novel Gram-negative propanotrophic bacterial isolate

256th National Meeting (2018)

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