Chlordimeform Degradation by a Mixed Culture of Bacillus sp., Acinetobacter sp. and Rhodococcus rhodochrous

Abstract

Chlordimeform is an insecticide extensively applied causing serious environmental pollution. In this study, some bacterial strains, i.e., Bacillus sp. Cd1, Acinetobacter sp. Ca3 and Rhodococcus rhodochrous Ct2 isolated from soil were determined for their degradability towards the compound. Bacillus sp. Cd1 first transformed the substrate into 4-chloro-2-methylaniline and 3-chlorotoluene, and then slowly degraded the metabolites mainly via meta-cleavage pathway. By contrast, Acinetobacter sp. Ca3 slowly transformed chlordimeform but quickly degraded 4-chloro-2-methylaniline through ortho-cleavage pathway, while R. rhodochrous Ct2 showed rapid degradation of 3-chlorotoluene through the meta-cleavage pathway. The degradation kinetics for chlordimeform of the mixed culture followed the Edwards model with the maximum degradation rate being 10.49 ± 0.11 mM/day. Immobilization of the mixed culture in rice straw showed effective degradation, with almost complete degradation at the 6-th cycle using a pack-packed bed bioreactor. The cultivation with peanut and water spinach association with inoculation of the mixed culture enhanced the degradation of the compound in soil. This study elucidates the synergistic interaction among isolated bacteria to enhance degradation of chlordimeform and its metabolites. The cooperation among isolated bacteria, plant cultivation and indigenous microorganisms also increased the insecticide degradation in soil.