Evaluation of organophosphorus pesticide biodegradation by halophilic bacteria

Abstract

Introduction: Organophosphorus pesticides are used extensively in agriculture. Most of them are released into the environment and have harmful effects on the health of ecosystems, wildlife and humans. Due to the increase of the salinity in the agriculture, especially drainage waters and the need for cleaning and reuse of the water due to water shortages, there is an increased demand for new treatment techniques. Bioremediation is the efficient and environmentally friendly way and can be used to remove these contaminants. Materials and methods: Halophilic bacteria that have the ability to use organophosphorus pesticide chlorpyrifos as the sole source of carbon, were isolated through targeted enrichment. Based on the higher growth and tolerance in the presence of the pesticide, one isolate was selected. The ability of the selected strain to degrade chlorpyrifos was examined by gas chromatography-mass spectrometry analysis. The strain was identified by molecular method. To determine the optimal growth conditions, as an indicator of optimal pesticide removal, factors such as temperature, pH, concentration of salt and chlorpyrifos in the presence of pesticide (sole source of carbon) were examined. Results: The selected isolatenamed CDB5 showed 25.23% removal of chlorpyrifos in the basic conditions without addition of growth factors in 10 days. The molecular identification revealed that this halophilic strain belongs to the genus Halomonas sp. Investigation of the effect of factors in the presence of chlorpyrifos as the sole source of carbon showed that the strain has the highest growth at temperature 35℃, pH7, salt concentration of 10% and the chlorpyrifos concentration of 600 mg/l. Discussion and conclusion: Halophilic bacteria due to compatibility with the salty condition, can be a good option for the removal of organophosphorus pesticides in the contaminated salty environments.

Keywords

• Halophiles
• Pesticides
• Chlorpyrifos
• Bioremediation
• GC-MS