Biodegradation of chlorpyrifos in soil by enriched cultures.

Three aerobic bacterial consortia, AC, BC, and DC, developed from pesticide-contaminated soils of Punjab were able to degrade chlorpyrifos after 21 days of incubation in basal medium by 54, 46, and 61% and chlorpyrifos (50 mg/L) in soil after 30 days by 50, 56, and 64%. Pseudomonas aeruginosa, Bacillus cereus, Klebsiella sp., and Serratia marscecens obtained from these consortia showed 84, 84, 81, and 80% degradation of chlorpyrifos (50 mg/L) in liquid medium after 20 days and 92, 60, 56, and 37% degradation of chlorpyrifos (50 mg/L) in soil after 30 days. Populations of Bacillus cereus, Klebsiella sp., and Serratia marscecens remained steady in soil experiments except for P. aeruginosa, where the population showed a substantial increase. Formation of 3,5,6-trichloro-2-pyridinol, the major metabolite of chlorpyrifos degradation, was observed during the degradation of chlorpyrifos by P. aeruginosa, which disappeared to negligible amounts.