Selective removal of the non-herbicidal (S)-enantiomer of dichlorprop from agricultural soil by an in-situ enriched consortium

Rac-dichlorprop [( R , S )-2-(2,4-dichlorophenoxy)propanoic acid], a commonly used chiral phenoxyalkanoic acid herbicide, is frequently detected in various environments, posing threats to human health and environmental safety. The ( S )-enantiomer of dichlorprop shows a lower herbicidal activity but a higher toxicity as compared to the ( R )-enantiomer of dichlorprop. It is of great importance to enantioselectively remove the non-herbicidal ( S )-dichlorprop from the rac -dichlorprop in the application sites. In this study, the dissipation of ( R )- and ( S )-dichlorprop in an agricultural soil was investigated. We found that the dissipation rate of ( S )-dichlorprop was higher than that of ( R )-dichlorprop in an agricultural soil. Although the influences of different enantiomers of dichlorprop on soil bacterial community were not different, Sphingobium was significantly enriched in the ( S )-dichlorprop-treated soil as compared to ( R )-dichlorprop, indicating that Sphingobium species played important roles in the dissipation of ( S )-dichlorprop. Furthermore, a bacterial consortium containing Sphingobium sp. strain SP-2 (enantioselectively transforming ( S )-dichlorprop to 2,4-dichlorophenol) and Sphingopyxis sp. strain DP-21 (mineralizing 2,4-dichlorophenol), which synergistically mineralized the ( S )-enantiomer of dichlorprop, was isolated from the agricultural soil. Bioaugmentation with the in-situ isolated consortium (strains SP-2 and DP-21) resulted in the enhanced removal of the non-herbicidal ( S )-dichlorprop from the soil and in the adaptation of the inoculated degrading strains. This study offers new insights into the enhanced bioremediation of the non-herbicidal ( S )-dichlorprop contaminated soils while simultaneously ensuring environmental safety and crop yield.