The Degradation Capability of Bacillus alkalinitrilicus for Imidacloprid Bioremediation in Soil

Biodegradation of imidacloprid is reported in sterile sandy loam soil fortified @ 50, 100 and 150 mg kg⁻¹ insecticide along with 45x10⁷ colony forming unit (cfu) of Bacillus alkalinitrilicus. Soil samples were analyzed against those treated with the same doses of the insecticide but without inoculating the bacteria. The residues of imidacloprid and its metabolites were determined by high performance liquid chromatography employing photodiode array detector system and C₁₈ column. After 7 d of treatment, the total residues in soil treated with 50 mg kg⁻¹ imidacloprid were 40.30 mg kg⁻¹, compared with 36.01 mg kg⁻¹ in presence of bacteria. On the same day, the metabolites like 6-chloronicotinic acid, nitroguanidine, olefine, nitrosimine, urea and 5-hydroxy were detected in all the treatments. Among metabolites, urea, olefine and 6-chloronicotinic acid were found in major proportion while 5-hydroxy, nitrosimine and nitroguanidine were observed in minute amounts. The half-life of imidacloprid at 50 mg kg⁻¹ dose was 25 d and 30 d for both the 100 and 150 mg kg⁻¹ doses in the unamended soil. However, in amended soil, the half-life at 50 and 100 mg kg⁻¹ were 15 d and at 150 mg kg⁻¹, it was 17 d. B. alkalinitrilicus can thus be used for bioremediation of imidacloprid in soil.