A new endosulfan-degrading fungus, Mortierella species, isolated from a soil contaminated with organochlorine pesticides

Abstract

Two new aerobic endosulfan-degrading fungal strains, Mortierella sp. strains W8 and Cm1-45, were isolated from soil contaminated with organochlorine pesticides. This is the first report on the biodegradation of endosulfan by Zygomycota. The strains isolated in this work degraded more than 70% and 50% of a and b-endosulfan, respectively, over 28 days at 25°C, whereas 8.2 mM of each a and b-endosulfan was added as the initial concentration in liquid cultures. Only a small amount of endosulfan sulfate, a persistent metabolite, was detected in both cultures, while these strains could not degrade endosulfan sulfate when incubated with endosulfan sulfate as the initial substrate. Both strains generate endosulfan diol as a first step in the degradation of endosulfan and then undergo further conversion to endosulfan lactone. The formation of these intermediates was confirmed by GC-MS. Mortierella spp. might be present as hyphae in contaminated soil because they were isolated using the soil washing method; therefore, these Mortierella spp. strains have potential for the bioremediation of contaminated sites with endosulfan. © Pesticide Science Society of Japan Keywords: bioremediation, endosulfan, endosulfan diol, endosulfan sulfate, Mortierella.* To whom correspondence should be addressed. E-mail: ktakagi@niaes.affrc.go.jp Published online July 15, 2010 © Pesticide Science Society of Japan J. Pestic. Sci., 35(3), 326-332 (2010326-332 ( ) DOI: 10.1584 Original ArticleMaterials and Methods SoilsFour soil samples were used for the isolation of endosulfandegrading fungi. Three soil samples were collected from different agricultural sites (two in Kagoshima prefecture, one in Ehime prefecture) having a history of repeated endosulfan application until 2007 and 1990, respectively. One soil sample was collected from an old factory site (Niigata prefecture) contaminated with persistent organic pollutants (DDTs and HCHs). The basic properties of the four soils were determined and are shown in Table 1. Endosulfan was not detected from all soil samples, but endosulfan sulfate had accumulated in soils A and B at concentrations of 1.0 mg/kg (dry weight) and 0.53 mg/kg (dry weight), respectively. a-endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) (97% purity), b-endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9, 9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) (97% purity), and endosulfan sulfate (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3,3-dioxide) (98% purity) were purchased from Wako Pure Chemical Industries (Osaka, Japan), and endosulfan diol (1,4,5,6,7,7-hexachlorobicyclo[2.2.1]hept-5-ene-2,3-dimethanol) (98% purity), endosulfan ether (4,5,6,7,8,8-hexachloro-1,3,3a,4,7,7a-hexahydro-4,7-methanoisobenzofuran) (99% purity), and endosulfan lactone (4,5,6,7,8,8-hexachloro-4,7-methano1,3,3a,4,7,7a-hexahydroisobenzofuran-1-one) (98.5% purity) were purchased from Dr. Ehrenstorfer GmbH (Augsburg, Germany). Chemicals Microorgani...

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