Soil fungal strains degrading hexachlorocyclohexane isomers as potential bioresources for future mycoremediation applications

Soil microbiota is increasingly threatened by human activities and global change, especially due to persistent chemical contamination. Hexachlorocyclohexane (HCH) isomers are globally recognized as hazardous and highly persistent organic contaminants. Thanks to their resilience and metabolic versatility, soil fungi represent promising bioresources for HCH-contaminated soil bioremediation. For this study, soil samples were collected from two plots in the National Priority Site “Bacino del Fiume Sacco” in the Metropolitan City of Rome, sampling up to 100 cm. Samples were then divided into topsoil (TS) and subsoil (SS). Microbial community-level physiological profiles were assessed by Biolog EcoPlate™, revealing differences in metabolic activity between TS and SS communities. The fungal fraction was further investigated by quantifying CFUs/g of dry soil. To isolate fungal HCH-degrading strains, a selective enrichment procedure was performed using a mixture of HCH-isomers as sole carbon source, from which resulted several fungal isolates, predominantly belonging to Fusarium, Alternaria, and Acremonium-like genera, now preserved in the Fungal Biodiversity Laboratory Culture Collection (Sapienza University of Rome). To individually assess isolates’ ability to exploit HCH-isomers a multiwell assay was performed providing single isomers as sole carbon sources, revealing different activity depending on the isomer/isolate combination. Finally, the isolates were tested for biosurfactants production, as HCH-bioavailability enhancers. These results highlight the potential of selected fungal strains as candidates for future mycoremediation applications aimed at HCH-contaminated soils. Funder: Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4 - Call for tender No. 3138 of 16 December 2021, rectified by Decree n.3175 of 18 December 2021 of Italian Ministry of University and Research funded by the European Union – NextGenerationEU; Award Number: Project code CN_00000033, Concession Decree No. 1034 of 17 June 2022 adopted by the Italian Ministry of University and Research, CUP B83C22002950007, Project title “National Biodiversity Future Center - NBFC"