Biodegradation of organophosphate pesticide chloropyrifos by Egyptian bacterial isolates.

Sixteen microbial isolates capable of growing on Dursban as a secondary substrate were isolated from three soil and sewage water samples collected from different localities polluted with pesticides. Six developed isolates only were capable of biodegrading Dursban and utilizing it as only sole source of carbon, energy and phosphorus. The six bacterial isolates were managed to grow on enrichment medium containing Dursban up to 40 ml/liter, for seven days at 25 degrees C. Each isolate exhibited growth and degradation of Dursban concentrations that best bacteria were identified as Pseudomonas stutzeri S7B4 and Flavobacterium balustinum S8B6. These two bacterial isolates were subjected to some environmental and nutritional parameters that affect the biodegradation process of Dursban. The optimum conditions includes :incubation period, 7 days; Dursban concentrations, 10 ml/l; inoculum size, 4 ml/l; incubation temperature, 35 degrees C; optimum pH value, 7; carbon source, fructose and ribose, respectively; nitrogen source, urea and peptone, respectively; amino acid, histidine; and vitamin, yeast extract, under shaking condition (200 rpm). Only the most potent microbial isolate Pseudomonas stutzeri was grown on their own mineral salts medium which contained 40 mlM/l in case of Dursban in the absence and presence of fructose as the best carbon source for two time intervals i.e. 7 and 15 days. Absence of phosphorus and the presence of many oxidized compounds revealed that the ability of P. stutzeri to biodegrade and detoxify Dursban using it as the sole phosphorus, carbon and energy sources. GC-MS analysis of all three treatments of Dursban-bioremediation process showed no detection of any phosphorus compounds especially Dursban in the three treatments, indicated that both bacterial strains i.e. P. stutzeri S7-B4 and F. balustinum S8B6 were able to utilize Dursban pesticide as carbon and phosphorus sources. Thus, it is possible to use both bacterial strains in the bioremediation of pesticides especially Dursban-contaminated sites.