Biodegradation of α-endosulfan via hydrolysis pathway by Stenotrophomonas maltophilia OG2

Stenotrophomonas maltophilia OG2 was isolated from the intestine of cockroaches that was collected from a cow barn contaminated some pesticides belong to pyrethroid and organochlorine groups. OG2 was able to degrade alpha-endosulfan in non sulfur medium (NSM) as a sole sulfur source for growth within 10 days of incubation. The effects of some growth parameters on endosulfan biodegradation by OG2 was studied and found that the biodegradation was significantly affected by the endosulfan concentrations, pH and temperature. Experimental results obtained in different conditions show that the optimum concentration of alpha-endosulfan, pH and temperature were 100 mg/L, 8.0 and 30 degrees C, respectively. Under these conditions, the bacterium degraded 81.53% of the alpha-endosulfan after 10 days. The concentration of alpha-endosulfan and its metabolites was determined by HPLC. Endosulfan ether, endosulfan lactone and endosulfan diol were the main metabolites in culture, but did not produce toxic metabolite, endosulfan sulfate. These results suggested that S. maltophilia OG2 degrades alpha-endosulfan via a hydrolysis pathway. The present study indicates that strain OG2 may have potential use in the biodegradation of pesticides contaminated environments.