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TECHNICAL REPORTS
Bioremediation and Biodegradation

Enrichment and Isolation of Endosulfan-Degrading Microorganisms

^a Dep. of Environmental Sciences, Univ. of California, Riverside, CA 92521
^b Dep. of Soil Science, Univ. of Agriculture, Faisalabad, Pakistan

* Corresponding author (william.frankenberger{at}ucr.edu)

Received for publication January 31, 2002. Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-benzo-dioxathiepin-3-oxide) is a cyclodiene organochlorine currently used as an insecticide all over the world and its residues are posing a serious environmental threat. This study reports the isolation and identification of enriched microorganisms, capable of degrading endosulfan. Enrichment was achieved by using the insecticide as either the sole source of carbon or sulfur in parallel studies. Two strains each of fungi (F1 and F4) and bacteria (BF2 and B4) were selected using endosulfan as a sole carbon source. A Pandoraea species (Lin-3) previously isolated in our laboratory using lindane (-HCH) as a carbon source was also screened for endosulfan degradation. F1 and F4 (Fusarium ventricosum) degraded -endosulfan by as much as 82.2 and 91.1% and ß-endosulfan by 78.5 and 89.9%, respectively, within 15 d of incubation. Bacterial strains B4 and Lin-3 degraded -endosulfan up to 79.6 and 81.8% and ß-endosulfan up to 83.9 and 86.8%, respectively, in 15 d. Among the bacterial strains isolated by providing endosulfan as a sulfur source, B4s and F4t degraded -endosulfan by as much as 70.4 and 68.5% and ß-endosulfan by 70.4 and 70.8%, respectively, after 15 d. Degradation of the insecticide occurred concomitant with bacterial growth reaching an optical density (OD₆₀₀) of 0.366 and 0.322 for B4 and Lin-3, respectively. High OD₆₀₀ was also noted with the other bacterial strains utilizing endosulfan as a sulfur source. Fungal and bacterial strains significantly decreased the pH of the nutrient culture media while growing on endosulfan. The results of this study suggest that these novel strains are a valuable source of potent endosulfan-degrading enzymes for use in enzymatic bioremediation.

Abbreviations: FTW, nutrient culture medium • LSU, large subunit • NSM, nonsulfur nutrient culture medium • OD, optical density