Degradation characteristics of a dibenzofuran-degrader Terrabacter sp. strain DBF63 toward chlorinated dioxins in soil

To obtain basic information towards applying a dibenzofuran (DF)-degrader Terrabacter sp. strain DBF63 to bioremediate dioxin-contaminated soil, we investigated the degradative potential of strain DBF63 for either chlorinated or polychlorinated dibenzo-p-dioxins and dibenzofurans (ClxDD/ClxDF) in soil. In the soil slurry system with a soil to water ratio of 1:5 (w/v), the DF-grown DBF63 cells degraded 90% of 1 ppm 2,8-Cl2DF, whereas only 40% of 1 ppm 2,3-Cl2DD during the 7-day incubation. The degradation rates of 2-ClDF, 2-ClDD, 2,8-Cl2DF and 2,3-Cl2DF by strain DBF63 in the soil slurry system (5-day incubation) were approximately 89%, 65%, 78% and 32%, respectively. These results suggest that strain DBF63 was able to degrade mono- to dichlorinated dibenzofurans more effectively than mono- to dichlorinated dibenzo-p-dioxins. Using the same soil slurry system, we performed a preliminary bioremediation experiment using the actual dioxin-contaminated soil at an incineration site. We found that approximately 10% of tetra- to hexa-chlorinated congeners was decreased by a single inoculation with DBF63 cells within a 7-day incubation.