Microbial degradation of organochlorine pesticide: 2,4-Dichlorophenoxyacetic acid by axenic and mixed consortium

The presence of 2,4-dichlorophenoxyacetic acid (2,4-D), an organochlorine herbicide, in the environment has raised public concern as it poses hazard to both humans and the ecosystem. Three potential strains having the capability to degrade 2,4-D were isolated from on site agricultural soil and identified as Arthrobacter sp. SVMIICT25, Sphingomonas sp. SVMIICT11 and Stenotrophomonas sp. SVMIICT13. Over 12 days of incubation, 81-90% of 100 mg/L of 2,4-D degradation was observed at 2% inoculum. A shorter lag phase with 80% of degradation efficiency was observed within 5 days when the inoculum size was increased to 10%. Six microbial consortia were prepared by combining the isolates along with in-house strains, Bacillus sp. and Pseudomonas sp. Consortia R3 (Arthrobacter sp. + Sphingomonas sp.), operated with 10% of inoculum, showed 85-90% degradation within 4 days and 98-100% in 9 days. Further, targeted exo-metabolite analysis confirmed the presence and catabolism of intermediate 2,4-dichlorophenol and 4-chlorophenol compounds.