Biodegradation of chlorpyrifos and malathion by Pseudomonas aeruginosa, Bacillus mycoides, and Bacillus cereus isolated from pesticides polluted soil in Sudan was studied in mineral salt media. Chlorpyrifos and malathion were incubated with each type with samples drawn at 0, 3, 7, 14 and 30 days for gas chromatographic analysis. Losses in the initial concentration, 1.142 mM L-1 for chlorpyrifos and 1.2121 mM L-1 for malathion, were measured and used to compute half-lives following biphasic model. GC-MS was used to identify major metabolites. Remaining amount recovered from media inoculated with P. aeruginosa ranged from 0.43 to 0.119 mM L-1 for chlorpyrifos and 0.544 to 0.145 mM L-1 for malathion. Whereas respective ranges recovered from media inoculated with B. mycoides and B. cereus were: 0.68 to 0.126 and 0.706 to 0.142 mM L-1 for chlorpyrifos and 0.61 to 0.23, 0.51 to 0.117 mM L-1 for malathion. No metabolites were detected in B. mycoides cultures, whereas a major metabolite of chlorpyrifos (hydroxy-O-ethyl-O-3,5,6-trichloropyridin-2-yl phosphorothioate) was detected in P. aeruginosa culture. Two metabolites of malathion, malathion monoacid and diacid, were detected in B. cereus culture. Results indicated the potential capability of these microorganisms in complete mineralization of chlorpyrifos and malathion as previously argued by Elsaid et al. (2010) and Shaer et al. (2013). Based on half lives, the degradation efficiency of these bacteria can be ordered as: P. aeruginosa > B. mycoides > B. cereus for chlorpyrifos and B. cereus > B. mycoides > P. aeruginosa for malathion.

Biodegradation of chlorpyrifos and malathion by three types of bacteria isolated from pesticides polluted soils in the Sudan

248th National Meeting (2014)

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