Biodegradation of chlorpyrifos by an optimized <i>Bacillus</i> consortium isolated from pesticide-contaminated soils of Kerala, India
Edna Mary Varghese, Shalu Sivadas, C Joshi Suresh, U. Devikrishna, Kalieswaran Vidhya, K. P. Akhil, M. S. Jisha
Abstract
The current study attempted to develop a bacterial consortium which can degrade chlorpyrifos pesticide efficiently. Five morphologically different bacterial strains, capable to tolerate high chlorpyrifos concentration, were isolated from pesticide-contaminated soil. Further, possible combinations of the isolates were formed and each combination was screened and chlorpyrifos degradation percentage and half-lives were calculated. The consortium CON11, comprising of four isolates (CP28, CP30, CP31, and CP34) showed the highest chlorpyrifos degradation. The individual independent variables of chlorpyrifos degradation by CON11 viz. temperature (°C), pH, incubation time (days) and pesticide concentration (ppm) were optimized using one-factor at-a-time experiments. The consortium isolates were then identified by the molecular tools 16S rRNA gene typing and the sequences were submitted to GenBank. The four bacterial isolates thus identified are Bacillus amyloliquefaciens CP28 (MH667455), Bacillus pumilus CP30 (MH667456), Bacillus marisflavi CP31 (MN715880), and Bacillus subtilis CP34 (MH667458). These isolates which comprise CON11 consortium could degrade 91% of 100 ppm chlorpyrifos after 6 days of incubation at 30 °C and pH 7 with a half-life of 1.73 days indicating the promising potential of the consortium, CON11, in the cleanup of chlorpyrifos contaminated sites.