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

Endosulfan is a broad-spectrum cyclodiene insecticide that has been used extensively for over 30 years on a variety of crops. It is a mixture of two stereoisomers, a and b endosulfan, in a ratio of 7 : 3. Its toxicity is extremely high against fish and aquatic invertebrates, and it has increasingly been implicated in mammalian gonadal toxicity, genotoxicity and neurotoxicity; however, endosulfan is still used as a pesticide in agriculture because it is more biodegradable than other cyclodiene pesticides with soil half-lives of 60 to 800 days. In general, both isomers are degraded via sulfur oxidation or hydroxylation of the sulfite moiety to form the toxic metabolite endosulfan sulfate, or by hydrolysis to form the non-toxic metabolite endosulfan diol. In the environment, endosulfan sulfate is the major residue detected in soils and in plant and animal tissues after exposure to endosulfan. Microbial degradation is a cost-effective and efficient way of remediating contaminated environments, and there have been many reports on the degradation of endosulfan using bacteria; however, there are few reports on the degradation of endosulfan using fungi. Previous studies have shown that Phanerochaete chrysosporium, Trichoderma harzianum and Aspergillus terreus are able to degrade endosulfan. P. chrysosporium and T. harzianum generated endosulfan sulfate as the principal metabolite of endosulfan degradation. Chlorinated pesticides, such as dieldrin, endorin, heptachlor, BHC and DDT, have been used extensively for the protection of crops and prevention of vector-borne disease. Their use has been prohibited in many countries since the 1970s because of their biological magnification, high toxicity and persistence in the environment. In 2004, they were assigned as persistent organic pollutants (POPs). Endosulfan is a compound used with caution and it is currently being discussed whether to designate it as POPs. The objective of this study was to find a soil fungus or soil fungi which can degrade endosulfan without generation of the toxic metabolite endosulfan sulfate. A new endosulfan-degrading fungus, Mortierella species, isolated from a soil contaminated with organochlorine pesticides