Degradation of Thiamethoxam by Mixed Culture of Phanerochaete sp. Th1 and Ensifer sp. Th2

Thiamethoxam is widely used to control pests, but it is harmful to nontargeted organisms and environments. In this study, the degradation of the insecticide was determined in liquid media, maize straw, and soil by fungal and bacterial strains, Phanerochaete sp. Th1 and Ensifer sp. Th2, isolated from soil. Both isolates utilized the compound used as a sole carbon, nitrogen, and sulfur source. The inoculation of both strains enhanced degradation rates compared to those of any single isolate. For example, the determination kinetics showed that the maximum degradation rates of Phanerochaete sp. Th1, Ensifer sp. Th2, and mixed culture of them were 0.53 +/- 0.05, 0.74 +/- 0.07, and 0.81 +/- 0.08 mg/day, respectively. In addition, Phanerochaete sp. Th1 showed effective degradability towards hemicellulose, cellulose, and lignin in maize straw. Moreover, the inoculation of both strains increased thiamethoxam degradation in maize straw during solid-state fermentation. The inoculation of isolated strains also enhanced degradation in soil. The determination of metabolites and Cl- generated during thiamethoxam degradation showed that the fungus dechlorinated initially, whereas the bacterial strain removed Cl- after some transformation steps. This study demonstrates that isolated fungal and bacterial strains are suitable for thiamethoxam degradation in liquid media, rice straw, and soil.