Bioremediation of Emamectin Benzoate-Contaminated Soil by Indigenous Fungi: Degradation Kinetics and Restoration of Soil Carbon and Nitrogen Cycling

Abstract

The excessive application of Emamectin benzoate (EMB) can impair soil health and disrupt key biogeochemical processes in the living cells. This study evaluated the bioremediation potential of three indigenous fungal isolates including: Alternaria infectoria, Lichtheimia corymbifera, and Aspergillus fumigatus in EMB-contaminated soil under increasing pesticide stress up to 250 mg L⁻¹. The EMB degradation kinetics were determined by HPLC, while soil respiration (CO₂ evolution) and urease activity were monitored as indicators of carbon and nitrogen cycling, respectively. At the recommended concentration 100 mg L⁻¹, fungal inoculation significantly enhanced EMB degradation, reducing the half-life from 4.70 days in the control to approximately 1.6 days. Under the lethal concentration 250 mg L⁻¹, A. infectoria maintained the highest degradation rate k = 0.388 day⁻¹ and the shortest half-life 1.79 days, compared with 5.84 days in the control. This isolate also produced the highest cumulative CO₂ emission 1680.9 mg kg⁻¹ soil, indicating efficient EMB mineralization. In contrast, A. fumigatus showed the greatest capacity to restore nitrogen cycling by sustaining urease activity and overcoming the initial inhibition phase. Overall, A. infectoria exhibited the strongest bioremediation potential, highlighting its suitability for the remediation of EMB-contaminated agricultural soils.