Simultaneous degradation of the pesticides methyl parathion and chlorpyrifos by an isolated bacterial consortium from a contaminated site

Abstract

The simultaneous degradation of the pesticide methyl parathion and chlorpyrifos was tested using a bacterial consortium obtained by selective enrichment from highly contaminated soils in Moravia (Medellin, Colombia). Microorganisms identified in the consortium were Acinetobacter sp, Pseudomonas putida, Bacillus sp, Pseudomonas aeruginosa, Citrobacter freundii, Stenotrophomonas sp, Flavobacterium sp, Proteus vulgaris, Pseudomonas sp, Acinetobacter sp, Klebsiella sp and Proteus sp. In culture medium enriched with each of the pesticides, the consortium was able to degrade 150 mg l −1 of methyl parathion and chlorpyrifos in 120 h. When a mixture of 150 mg l −1 of both pesticides was used the percentage decreased to 72% for methyl parathion and 39% for chlorpyrifos. With the addition of glucose to the culture medium, the consortium simultaneously degraded 150 mg l −1 of the pesticides in the mixture. 4 treatments were carried out in soil that included the addition of glucose with microorganisms, the addition of sugar cane with microorganisms, microorganisms without nutrient addition and without the addition of any item. In the treatment in which glucose was used, degradation percentages of methyl parathion and chlorpyrifos of 98% and 97% respectively were obtained in 120 h. This treatment also achieved the highest percentage of reduction in toxicity, monitored with Vibrio fischeri.