Biodegradation of fenthion and temphos in liqud media by Bacillus safensis isolated from pesticides polluted soil in the Sudan

The objective of this study was to evaluate the capability of the bacteria Bacillus safensis strain FO36b T isolated from pesticide-polluted soil in degrading fenthion and temphos in mineral salt media (MSM). Fenthion and temphos were incubated with the isolated bacteria. Samples were drawn at 0, 3, 7, 14, and 30 days to analyze residual fenthion and temphos content with gas chromatography (GC) and high-performance liquid chromatography (HPLC), respectively. The loss of the initial pesticide concentration (400 mg/L) over time was determined and used to compute the half-lives using a biphasic model. Gas chromatography-mass spectrometry (GC-MS) was used to identify the major metabolites as well as to re-confirm the identity of starting material (fenthion). The results showed that the bacterium was still viable at the end of each incubation period. The biodegradation of fenthion and temphos followed a biphasic model. The half-lives of fenthion in the first and in the second phase were 0.29 and 3.69 days, respectively, whereas the corresponding values for temphos were 0.11 and 1.15 days. Only one metabolite "iso-fenthion" (O, S-dimethyl O-[3-methyl-4-(methylthio)phenyl] phosphorothioate) was detected in fenthion culture, while no metabolites were detected in temphos culture. Based on the halflives, this bacterium was able to degrade temphos at a faster rate than fenthion.