Degradation of 1,4-dioxane by Newly Isolated Acinetobacter sp. M21 with Molasses as the Auxiliary Substrate

The elimination of 1,4-dioxane (dioxane), a persistent organic pollutant, is a great challenge owing to its high hydrophilicity and chemical stability. Cometabolic bioremediation technology is an effective approach to remove many organic pollutants. Because of its eco-friendly and inexpensive properties, molasses is widely used as an auxiliary biomaterial to clean up compound-contaminated sites. In this study, a newly isolated bacterium Acinetobacter sp. M21 could effectively remove dioxane using molasses without any apparent lag phase. Under the optimized molasses dosage of 0.3%, M21 could remove 500 mg/L dioxane by 60.0 ± 2.8% within 20 days with a maximum dioxane degradation rate of 1.3 ± 0.2 mg-dioxane/L/h in the first day, and exhibited extraordinary dioxane tolerance up to 1,000 mg/L, while so high dose of dioxane negatively affected the cell growth. The degradation pathway of dioxane was also determined, and was supported by the detection of 2-hydroxyethoxyacetic acid as the key metabolite of dioxane. High level degradation activity of M21 to 20 mg/L dioxane was maintained over a variable of pH (5-11), temperatures (15-45°C), and salinities (up to 8%, as NaCl wt). This is the first report linking the cometabolism of dioxane and molasses by Acinetobacter sp. M21, a bacterium that shows great potential for field dioxane bioremediation.