Lessons learned from two applied approaches for treatment of aged DDT-contaminated soil with white-rot fungi

The persistence of dichlorodiphenyltrichloroethane (DDT) in soil poses a serious environmental challenge due to its toxicity, hydrophobicity, and resistance to degradation. White-rot fungi, such as Pleurotus ostreatus, show potential for bioremediation of persistent organic pollutants via ligninolytic enzymes. The aim of this study was to evaluate whether P. ostreatus spent mushroom substrate (SMS), used directly as a waste product from mushroom production and without pre-conditioning, could be applied to aged DDT-contaminated soil and result in measurable reductions in DDT and its transformation products (collectively referred to as DDX) in a pot-scale mesocosm experiment designed to mimic field application. We further evaluated whether pre-inoculated fungal substrates introduced into contaminated field soil could establish in the amended soil and be associated with measurable reductions in DDX under environmentally realistic conditions. Under the conditions tested, no measurable degradation of DDT or its transformation products was observed in either the pot experiment or the field trial. Considering that significant reduction in DDX has been observed in similar lab experiments with DDT-spiked soils elsewhere, the findings in this study highlight critical limitations to mycoremediation of aged DDT in soils under laboratory and field conditions tested in this study, particularly fungal viability, substrate quality, and soil colonization constraints. Rather than demonstrating treatment efficacy, this study identifies and outlines constraints that limited performance and provides transferable insights for the future development of white-rot fungal remediation strategies for aged DDT-contaminated soils under environmentally realistic conditions. It emphasizes the need to enhance fungal activity and enzyme production, for example through pre-conditioning of SMS, while also addressing the limited bioavailability of DDX in historically contaminated soils, which may constrain fungal access to the contaminants and reduce treatment efficacy in real-world settings.