Abstract

Chlorpyrifos (CP), a widely used organophosphate in Kenya, poses significant human health risks due to its high solubility. This study aimed to isolate CP-degrading bacteria from dairy farm soils in Nakuru County and develop bacterial consortia for efficient degradation. Soil samples were collected from six sub-counties: Molo, Njoro, Rongai, Subukia, Gilgil, and Naivasha. The enrichment culture technique using minimal salt medium (MSM) was employed to isolate CP-degrading bacterial strains. Seven bacterial strains were identified: Alcaligenes faecalis, Bacillus weihenstephanensis, Bacillus toyonensis, Alcaligenes sp., Pseudomonas sp., Pseudomonas japonicum, and Brevundimonas diminuta. Bacillus weihenstephanensis exhibited the highest individual degradation efficiency at 79.8%. Consortia treatments demonstrated enhanced degradation, with consortia M1, M2, and M3 achieving removal efficiencies of 91.3%, 92.48%, and 93.76%, respectively, and M5 achieving 95.32%. The study also monitored 3,5,6-trichloro-2-pyridinol (TCP), a CP metabolite, showing that consortia treatments significantly reduced TCP levels to near initial concentrations. Kinetic analysis revealed consortia had significantly shorter half-lives for CP degradation compared to individual isolates, indicating improved bioremediation potential. The findings underscore the potential of using tailored bacterial consortia for effective bioremediation of CP-contaminated environments. Future research should focus on field trials to validate these laboratory findings under real-world conditions and explore the genetic and enzymatic mechanisms underlying CP degradation.

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