Fungi in action against hexachlorocyclohexane: a focus on biosurfactants from fungal biodiversity

Hexachlorocyclohexane (HCH) is a highly persistent organic pollutant of global concern, involving severe risks for human health and ecosystem functioning. Mycoremediation represents a feasible nature-based solution for the restoration of soils polluted by HCH thanks to the ability of fungi to tolerate, bioaccumulate and degrade it. Known for its insecticidal properties of one of its isomers (γ-HCH), it has been used for a long time in European soils and despite the ban in the Stockholm Convention, high concentrations exceeding the threshold values have been found in many areas. One of this is the National Priority Site “Bacino del Fiume Sacco” within the Metropolitan City of Rome that has been selected as study area. Soil cores up to 1m of depth, divided in topsoil and subsoil samples, were collected from 2 plots. To isolate fungi able to utilize HCH as the sole C-source, an isolation in enrichment conditions was carried out providing an high concentration of isomers’ mixture (α-, β-, γ- and δ-HCH). A total of 49 fungal strains was isolated, mostly belonging to Fusarium and Alternaria genera. To evaluate the ability of these fungi to produce biosurfactants, metabolites that enhance HCH biodegradability, three tests were carried out: oil emulsification activity test, oil displacement test and drop collapse assay. The results of the assays showed the ability of some strains to produce biosurfactants, making them suitable candidates for further investigation.