HERBICIDE BIODEGRADATION POTENTIAL OF FUNGI ISOLATED FROM HERBICIDE-CONTAMINATED SOILS IN SELECTED OKITIPUPA LOCAL GOVERNMENT AREA FARMLANDS

Abstract

This study aims to isolate indigenous fungal species from paraquat-contaminated farmland in Okitipupa, Ondo State, Nigeria, and evaluate their capacity to biodegrade the non-selective herbicide Slasher Dichloride (paraquat, 276 g/L) to mitigate soil contamination and associated ecological and human health risks. Isolation and identification of fungi from paraquat-contaminated sites were carried out using standard cultural and molecular methods, biodegradation assays were conducted in Mineral Salt Medium (MSM) with 100 mg/L paraquat as the sole carbon source, incubated at pH 6.3, 31°C, 120 rpm for 7 days while process optimization of inoculum concentration (1–5 % v/v) was done using response surface methodology, with fungal growth monitored by optical density at 600 nm (OD 600). Optimal fungal growth occurred at a 1 % (v/v) inoculum for Aspergillus fumigatus (0.092 AU), Aspergillus niger (0.085 AU), Aspergillus nidulans (0.078 AU), and Penicillium allii (0.050 AU), whereas Trichoderma harzianum (0.042AU) peaked at 3 % (v/v). The degradation efficiency ranked as follows: A. fumigatus > A. niger > A. nidulans > P. allii > T. harzianum. It was then concluded that the isolates have strong potential for the development of myco-based bioremediation strategies to restore herbicide-polluted soils in Okitipupa and similar agrarian regions.