Endosulfan is an organochlorine insecticide whose persistence and toxicity pose a serious environmental threat to humans and other living organisms in the ecosystem. This research investigates the isolation of natural fungi capable of biodegrading endosulfan into a less-toxic metabolite. Sixty-four isolates of soil fungi, white-rot fungi and endophytic fungi were screened for their degradation ability using thin layer chromatography (TLC) analysis as a qualitative measurement for the primary degradation test. It was found that after 20 days of incubation in Czapek’s Dox medium, the fungus isolate W2, which was isolated from a basidiocarp from Doi Suthep-Pui National Park in Chiangmai Province, yielded positive results by transforming endosulfan into the less- toxic metabolite, endosulfan diol. The secondary degradation test, performed with a gas chromatography (GC) analysis as a quantitative measurement of endosulfan degradation for 30 days of incubation, indicated that endosulfan concentration decreased gradually after spiking into the medium with the fungus isolate W2. The disappearance of endosulfan occurred after 21 days of incubation, with the formation of endosulfan diol after 3 days of incubation. The result of degradation test related directly to the growth of the fungus. The optimum growing and degrading condition for the fungus isolate W2 were attained at 98.88 percent of degradation efficiency using a solution of 50 milligrams per liter of endosulfan and 2 percent glucose at pH 7. Morphological study and internal transcribed spacer (rRNA) gene sequencing analysis indicated that fungus isolate W2 revealed a high sequence similarity (93-95 percent) with the genus Trametes.
