Microbial Degradation of Acetamiprid by Ochrobactrum sp D-12 Isolated from Contaminated Soil

Neonicotinoid insecticides are one of the most important commercial insecticides used worldwide. The potential toxicity of the residues present in environment to humans has received considerable attention. In this study, a novel Ochrobactrum sp. strain D-12 capable of using acetamiprid as the sole carbon source as well as energy, nitrogen source for growth was isolated and identified from polluted agricultural soil. Strain D-12 was able to completely degrade acetamiprid with initial concentrations of 0-3000 mg.L-1 within 48 h. Haldane inhibition model was used to fit the special degradation rate at different initial concentrations, and the parameters q(max), K-s and K-i were determined to be 0.6394 (6 h)(-1), 50.96 mg.L-1 and 1879 mg.L-1, respectively. The strain was found highly effective in degrading acetamiprid over a wide range of temperatures (25-35 degrees C) and pH (6-8). The effects of co-substrates on the degradation efficiency of acetamiprid were investigated. The results indicated that exogenously supplied glucose and ammonium chloride could slightly enhance the biodegradation efficiency, but even more addition of glucose or ammonium chloride delayed the biodegradation. In addition, one metabolic intermediate identified as N-methyl-(6-chloro-3-pyridyl)methylamine formed during the degradation of acetamiprid mediated by strain D-12 was captured by LC-MS, allowing a degradation pathway for acetamiprid to be proposed. This study suggests the bacterium could be a promising candidate for remediation of environments affected by acetamiprid.