Banafshe Nadalian - Faculty of Biological Science, Shahid Beheshti University, GC, Tehran, Iran.
Mohsen Shahriari Moghadam - Department of Environment, Faculty of Natural Resources, University of Zabol, Zabol, Sistan va Blaoochestan, Iran
Gholamhossein Ebrahimipour - Faculty of Biological Science, Shahid Beheshti University, GC, Tehran, Iran

The global use of pesticides has resulted in the contamination of various ecosystems worldwide. The impact of these pesticides can be reduced through bioremediation. The factors that influence the biodegradation rate include the isolation of efficient bacteria for use in remediation and the determination of optimal biodegradation conditions. In this study, malathion degrading bacteria were isolated from agricultural soil samples taken from the Arvandkenar region in Iran. To optimize the biodegradation of malathion by an isolated strain, the effect of four parameters (temperature, salinity, NH4Cl and K2HPO4) was evaluated while considering protein concentrations at different times. The malathion remaining in the media was measured using the gas chromatography method. A gram-negative bacterium strain BNA1 with malathion biodegrading ability was isolated from the soil sample which showed a 99% similarity to Serratia marcescens. The optimum biodegradation condition occurred at a temperature = 30 ˚C, salinity = 0 %, NH4Cl = 0.25 g/L and K2HPO4 = 0.25 g/L. A biodegradation efficiency of 65% was obtained under the abovementioned condition. The results of this study revealed the significant capability of BNA1 in the biodegradation of malathion. Therefore, the use of an isolated strain may be considered as an important tool in the bioremediation of pesticidecontaminated soil.

Biodegradation ،Malathion ،Optimization ،Pesticide،Serratia marcescens