Biodegradation of dieldrin by a soil fungus isolated from a soil with annual endosulfan applications

An aerobic dieldrin-degrading fungus, Mucor racemosus strain DDF, was isolated from a soil to which endosulfan had been annually applied for more than 10 years until 2008. Strain DDF degraded dieldrin to 1.01 μM from 14.3 μM during a 10-day incubation at 25 °C. Approximately 0.15 μM (9%) of aldrin trans-diol was generated from the dieldrin degradation after a 1-day incubation. The degradation of dieldrin by strain DDF was detected over a broad range of pH and concentrations of glucose and nitrogen sources. Extracellular fluid without mycelia also degraded dieldrin. Strain DDF degraded not only dieldrin but also heptachlor, heptachlor epoxide, endosulfan, endosulfan sulfate, DDT, and DDE. Endosulfan sulfate and heptachlor were degraded by 0.64 μM (95%) and 0.75 μM (94%), respectively, whereas endosulfan and DDE were degraded by 2.42 μM (80%) and 3.29 μM (79%), respectively, and DDT and heptachlor epoxide were degraded by 6.95 μM (49.3%) and 5.36 μM (67.5%), respectively, compared with the control, which had a concentration of approximately 14 μM. These results suggestthat strain DDF could be a candidate forthe bioremediation of sites contaminated with various persistent organochlorine pesticides including POPs.