First Report of Imidacloprid Biodegradation by Cladosporium cladosporioides: Kinetic Modeling, Transformation Products, and Toxicity Reduction

This study reports, for the first time, the aerobic degradation of imidacloprid by a native fungal strain of Cladosporium cladosporioides, isolated and identified using ITS region sequencing (ITS1/ITS4). Degradation experiments were conducted in aqueous batch cultures supplemented with glucose using initial imidacloprid concentrations of 20, 40, and 100 mg L−1. After 10 days, degradation efficiencies reached 71%, 56%, and 30%, respectively, with a maximum degradation rate of 2.66 mg L−1 d−1 at 40 mg L−1. Growth inhibition by imidacloprid was accurately described by the inhibited Monod model. Laccase activity was strongly correlated with imidacloprid degradation kinetics. Metabolites including 5-hydroxyimidacloprid, imidacloprid olefin, and 6-chloronicotinic acid were identified using LC-MS/MS and FTIR analyses, suggesting a plausible metabolic degradation pathway. Ecotoxicological evaluation using Eisenia fetida avoidance tests indicated reduced toxicity of transformation products compared to the parent compound. These findings lay the groundwork for the application of C. cladosporioides, suggesting it may have potential for the fungal-based treatment of pesticide-contaminated aqueous environments and agricultural effluents.