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 degrees 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.

Automated summary

In this study, a newly isolated bacterium Acinetobacter sp. M21 was found to effectively remove dioxane using molasses without any apparent lag phase. The M21 strain could remove a significant amount of dioxane within a short period of time and exhibited high tolerance to high doses of dioxane. The degradation pathway of dioxane was determined and the potential of Acinetobacter sp. M21 for dioxane bioremediation was highlighted.