Identification and characterization of 1,4-dioxane-degrading microbe separated from surface seawater by the seawater-charcoal perfusion apparatus.

To determine the concentration of soluble 1,4-dioxane during biodegradation, a new method using of high-performance liquid chromatography equipped with a hydrophilic interaction chromatography column was developed. The developed method enabled easy and rapid determination of 1,4-dioxane, even in saline medium. Microbes capable of degrading 1,4-dioxane were selected from the seawater samples by the seawater-charcoal perfusion apparatus. Among 32 candidate 1,4-dioxane degraders,, strain RM-31 exhibited the strongest 1,4-dioxane degradation ability. 16S rDNA sequencing and the similarity analysis of strain RM-31 suggested that this organism was most closely related to Pseudonocardia carboxydivorans. This species is similar to Pseudonocardia dioxanivorans, which has previously been reported as a 1,4-dioxane degrader. Strain RM-31 could degrade 300 mg/L within 2 days. As culture incubation times increasing, the residual 1,4-dioxane concentration was decreasing and the total protein contents extracted from growth cells were increasing. The optimum initial pH of the broth medium and incubation temperature for 1,4-dioxane degradation were pH 6-8 and 25 °C. The biodegradation rate of 1,4-dioxane by strain RM-31 at 25 °C in broth medium with 3 % NaCl was almost 20 % faster than that without NaCl. It was probably a first bacteria from the seawater that can exert a strong degrading ability.