Evaluating a preparation of malathion tolerant Aspergillus niger MRU01 for accelerated removal of four organophosphorus insecticides

BACKGROUND: Microbial degradation of organophosphorus (OP) insecticides has emerged as an efficient and cost‐effective technology for removal of pesticide residues from soil. Malathion‐tolerant Aspergillus (Aspergillus niger MRU01) was developed, mass cultured, harvested, mixed with coir pith at 3% on dry weight basis, shade‐dried aseptically to a 5% moisture level and stored for 60 days. The growth, metabolic activity and insecticide removal efficiencies of the preparation were evaluated at 15‐day intervals. RESULTS: No significant change in the growth performance was observed up to 45 days of storage, after which viability decreased. The activities of carbohydrate enzymes (cellulase, invertase and amylase) and protein and carbohydrate contents of the preparation, however, did not significantly change during the experimental period. The preparation showed accelerated activities of esterases and phosphatases after treatment with malathion (500 μmol L⁻¹), parathion (470 μmol L⁻¹), chlorpyrifos (260 μmol L⁻¹) and dimethoate (680 μmol L⁻¹). The highest activity of the esterase and phosphatase enzymes was observed with malathion and the minimum with parathion treatment. Nearly 70% of the applied malathion was removed from the medium by the preparation during 5 days of incubation followed by dimethoate (68%), chlorpyrifos (58%) and parathion (54%). CONCLUSIONS: The fungal preparation was highly effective in removing malathion as well as the other three OP insecticides. A storage period of 45 days may be considered ideal for maintaining the preparation in the active state, and is recommended for field application after evaluating its efficacy under field conditions. © 2021 Society of Chemical Industry