Micropollutants are a problem, but the fungal kingdom can help to solve it

Life on earth depends on freshwater, but this resource is more and more under pressure. Continuous discharge of polluted wastewater can cause significant environmental impacts on surface and groundwater, mainly due to the so-called Contaminants of Emerging Concern (CECs). Europe is taking action, with proposal aiming at the “polluter pays principle”, forcing pharma and cosmetic companies to cover the extra costs to clean urban wastewater. Wastewaters treatment plant, and especially their sludge, are an accumulation point of micropollutants, causing their complex microbial community to adapt. SusWater project aims to study this biodiversity and its powerful enzymatic cascade. The fungal community of the contaminated sludge was studied using liquid enrichment technique, using CECs commonly found in wastewaters treatment plants. Overall, 104 fungi were isolated, mostly belonging to the Ascomycota phylum. Surprisingly Basidiomycetes (9%) and Mucoromycetes (7%) were quite abundant. The isolated fungi were tested for their capabilities to degrade CECs. The removal efficiency was evaluated with a proper HPLC-UV detection method. Fungi isolated from this extreme environment must have developed peculiar metabolic skills and were indeed capable of degrading the target CECs. Notably, the degradation yields were strain dependent, but also CECs dependent. For instance, fungi easily attacked estriol and diclofenac, while fungi were almost ineffective against carbamazepine. Overall, 30% of fungi halved the concentration of one or more CECs with few strains capable of removing more than 70% of the CECs. The two best performing strains are currently under study to evaluate their strength in a more complex systems, where the transformation of CECs is followed in real wastewaters. Studies are also ongoing to study the transformation metabolites and to integrate these catalysts in intriguing technological solutions as hydrogels.