MICROBIOLOGICAL STUDIES ON BIOREMEDIATION OF PESTICIDE RESIDUES IN SOIL

Abstract

This work aimed to study the occurrence and microbial community sizes capable of utilizing and degrading the pesticides carbofuran and glyphosate in agriculture soils. Isolation and identification of some pesticide-degrading bacteria was carried out. In addition, the degradation frate and byproducts of carbofuran was also determined. 125 commercial­ glyphosate utilizing isolates as well as 96 commercial-carbofuran utilizing isolates were obtained. Only 68 and 54 isolates able to utilize crude glyphosate and carbofuran respectively at 100 ppm active ingredient concentration as sole carbon and nitrogen source. Five isolates consider as good growing on either carbofuran or glyphosate at 100 and 500 ppm were selected. Acording to their • molecular characteristics, they were identified as Acinetobacter lwoffii (IOF), Agrobacterium tumefaciens (11M), Ochrobactrum anthropi (17N), Escherichia coli (23B) and jAgrobacterium tumefaciens (26M). Carbofuran degradation in sterile and non sterile soil inoculated with these five isolates (individually) were estimated and the high degradation rate was observed in sterile soil inoculated with the strain Acinetobacter lwoffii (I OF) which achieve 50.97% and 88.5% degradation after 10 and 20 days respectively. Carbofuran degradation in non sterile soil was lower than in sterile one inoculated with the same strain and that could be attributed to the competition between bacterial inoculurns and the natural microflora in soil. The byproduct of carbofuran degradation in sterile soil inoculated with either the strain Acinetobacter lwoffii (!OF) or the strain Ochrobactrum anthropi (17N) was determined and it was found that carbofuran phenol is the main product of carbofuran hydrolysis in soil.