Carboxylesterases from bacterial enrichment culture degrade strobilurin fungicides

Strobilurin fungicides are a class of persistent fungicides frequently detected in the environment. Microbes can effectively degrade strobilurins, but the mechanisms are complex and diverse. Compared with isolated strains, bacterial consortia are more robust in terms of the degradation of multiple pollutants. The enrichment culture XS19 is a group of bacterial strains enriched from soil and degrades six strobilurins at 50 mg/L within 8 d, including azoxystrobin, picoxystrobin, trifloxystrobin, kresoxim-methyl, pyraclostrobin and enestroburin. LC-Q-TOF-MS analysis confirmed that XS19 can demethylate these strobilurins via hydrolysis of the methyl ester group. Analysis of the bacterial communities suggested that Pseudomonas (69.8%), Sphingobacterium (21.2%), Delftia (6.3%), and Achromobacter (1.6%) spp. were highly associated with the removal of strobilurins in the system. Metagenomics-based comprehensive analysis of XS19 suggested that carboxylesterases in Pseudomonas and Sphingobacterium play a central role in the catabolism of strobilurins. Moreover, the carboxylesterase inhibitor bis-p-nitrophenyl phosphate inhibited the degradation activity of strobilurins in XS19. This work proved that XS19 or carboxylesterases can effectively hydrolyze strobilurins, providing a reliable bioremediation paradigm.