Biodegradation of chlorpyrifos and 3, 5, 6‐trichloro‐2‐pyridinol by a novel rhizobial strain <scp><i>M</i></scp><i>esorhizobium</i> sp. <scp>HN3</scp>

Abstract

Abstract A chlorpyrifos ( CP ) and 3,5,6‐trichloro‐2‐pyridinol ( TCP ) degrading bacterial strain, M esorhizobium sp. HN3 , was isolated and characterized. M esorhizobium sp. HN3 degraded CP efficiently up to 400 mg/ L initial concentration at wide range of temperatures (30–40° C ) and pH (6.0–8.0). However, optimal degradation of CP was achieved at 37°C and neutral pH (7.0) at an initial inoculum density 2 × 10 7 colony forming unit/m L of culture medium. Kinetic parameters for CP degradation by M esorhizobium sp. HN3 were estimated at different initial concentrations. Cultures exhibited significant variation ( P ≤ 0.05) in the specific growth rate (μ), cell mass formation rate ( Q X ) and the substrate uptake rate ( Q S ) during degradation of CP . The values of kinetic parameters increased up to 100 mg/ L CP and decreased at higher concentration. Investigation of degradation metabolites indicated that CP is converted to diethylthiophosphate and TCP that leads to the formation of 3,5,6‐trichloro‐2‐methoxypyridine.