A study on bioremoval of a neonicotinoid insecticide, imidacloprid, by a newly isolated Acremonium sclerotigenum

A neonicotinoid insecticide, imidacloprid (IMI), has been widely used by seed treatment to control the sucking and biting insects since the nineties. Although it has been regarded as a highly recalcitrant pesticide, with reports of half-lives in the soil of 174 days and its use was banned in several countries for use on several crops, there is a limited number of reports on its mycoremediation. Considering also the difficulties in the control of its illegal use in some countries, seventeen fungal strains were isolated and tested for their IMI removal capacity in the current study, and Acremonium sclerotigenum was selected for further experiments. This is the first report indicating the usability of this biomass material cultivated in the molasses medium for IMI removal. Effect of some parameters on bioremoval rate, such as pH (4, 5, 6, 7), pesticide concentration (2.6, 6.7, 18.3, 33.9 and 44.0 mg/L), incubation time (48, 96 and 144 h), and amount of inoculum were tested. The maximum specific IMI uptake was obtained as 15.4 mg/g at 33.9 mg/L IMI concentration. The highest bioremoval rates observed for 2.6 and 6.7 mg/L pesticide levels were 100% at the end of 48 h at pH 6. The fungus could also remove 8.9% of 44.0 mg/L IMI at 96 h. This study suggests that A. sclerotigenum holds the potential for effective removal of IMI from the affected environment.