Biodegradation of endosulfan and pendimethalin by three strains of bacteria isolated from pesticides-polluted soils in the Sudan

Biodegradation of endosulfan (alpha and beta) and pendimethalin by Bacillus safensis strain FO-36b(T), Bacillus subtilis subsp. inaquosorum strain KCTC 13429(T) and Bacillus cereus strain ATCC14579(T) isolated from pesticides- polluted soil was studied in mineral salt medium. Endosulfan and pendimethalin were incubated with the three bacterial strains with samples drawn at various intervals for GC analysis. Representative samples were subject to GC-MS analysis. The loss in the initial concentrations, 0.663 mM (alpha endosulfan), 0.319 mM (beta endosulfan) and 1.423 mM (pendimethalin), was monitored and used to compute the half-lives following biphasic model. Removal percentage of endosulfan and pendimethalin in the media inoculated with the bacterial strains ranged from 24 to 95% (alpha endosulfan), 21-91% (beta endosulfan) and 51-97% (pendimethalin), respectively. Despite the significant decrease in starting material in B. safensis cultures, no metabolites were detected, whereas two major metabolites of endosulfan, 1,2,3,4,7,7-hexachloro-5,6-dihydroxybicyclo{2.2.1}-2-heptene and 1,2,3,4,7,7-hexachloro-formaldehyde- 6-methylbicyclo{2.2.1}-2-heptene, were detected in the B. subtilis cultures, and one metabolite of pendimethalin metabolite; N-(1-ethylpropyl)-3-methyl-2, 6-diaminobenzine, was detected in the B. cereus culture. Generally, the result indicates the potential capability of these microorganisms in complete mineralization of endosulfan and pendimethalin. Based on half-lives, the efficiency of bacterial strains can be ordered as follows: B. subtilis[B. cereus[ B. safensis for endosulfan and B. cereus[B. safensis[ B. subtilis for pendimethalin.