Characterization of 1,4-dioxane degrading microbial community enriched from uncontaminated soil

Abstract: 1,4-Dioxane is a contaminant of emerging concern that has been commonly detected in groundwater. In this study, a stable and robust 1,4-dioxane degrading enrichment culture was obtained from uncontaminated soil. The enrichment was capable to metabolically degrade 1,4-dioxane at both high (100 mg L⁻¹) and environmentally relevant concentrations (300 μg L⁻¹), with a maximum specific 1,4-dioxane degradation rate (q_max) of 0.044 ± 0.001 mg dioxane h⁻¹ mg protein⁻¹, and 1,4-dioxane half-velocity constant (K_s) of 25 ± 1.6 mg L⁻¹. The microbial community structure analysis suggested Pseudonocardia species, which utilize the dioxane monooxygenase for metabolic 1,4-dioxane biodegradation, were the main functional species for 1,4-dioxane degradation. The enrichment culture can adapt to both acidic (pH 5.5) and alkaline (pH 8) conditions and can recover degradation from low temperature (10°C) and anoxic (DO < 0.5 mg L⁻¹) conditions. 1,4-Dioxane degradation of the enrichment culture was reversibly inhibited by TCE with concentrations higher than 5 mg L⁻¹ and was completely inhibited by the presence of 1,1-DCE as low as 1 mg L⁻¹. Collectively, these results demonstrated indigenous stable and robust 1,4-dioxane degrading enrichment culture can be obtained from uncontaminated sources and can be a potential candidate for 1,4-dioxane bioaugmentation at environmentally relevant conditions. Key points: •1,4-Dioxane degrading enrichment was obtained from uncontaminated soil. • The enrichment culture could degrade 1,4-dioxane to below 10 μg L⁻¹. •Low K_sand low cell yield of the enrichment benefit its application in bioremediation.