Advanced treatment for removal of micropollutants in municipal effluents by fungal laccases

Pollution of water courses is generally caused by dyes, amines, phenols, heavy metals and surfactants as well as newly discovered contaminants as Endocrine Disrupting Chemicals (EDCs). Recently, the environmental concern rose since commonly used treatment processes are only partially effective towards these molecules, causing their progressive and constant accumulation into the environment (wastewaters, river waters and drinking water). A biological approach opens new scenarios for the treatment of wastewaters contaminated by micropollutants: enzymes are indeed able to degrade a wide spectrum of xenobiotics operating at various pH, temperatures and ionic strength. In the present study, a Trametes pubescens strain was opportunely stimulated in order to produce the necessary bulk enzymes. Thus the laccase-mediated treatment was used towards model and real solutions containing recognized EDCs, pharmaceuticals, PCPs, pesticides, etc. A multishot stir bar sorptive extraction with targeted in-situ derivatisation and a gaschromatography-mass spectrometric was used for analytes detection. This analytical method represents an innovative approach, enabling the contemporary detection of several target analytes in real municipal wastewaters: the matrix effect of the samples was negligible and micropollutants were quantifies up to ppt level (ng/l). Laccases demonstrated to be strongly active towards different molecules in spiked samples, being able to degrade at least 19 EDCs, belonging to different chemical classes. In most of the cases, the minimal effective enzymatic concentration was lower than 50 U/l and the analytes initial concentration was halved within the first 24 h. Due to the expected reduction when laccase crude extract is added to a complex matrix (i.e. wastewaters) with variable pH and active microflora, higher enzyme concentration (100 U/l) were adopted for the treatment of real wastewater sample. Laccases degraded most of the detected compounds in a range of 50-96% within 24 h. Besides, the analytes enzymes-catalysed conversion was followed by a significant abatement of the ecotoxicity and the estrogenic activity by means of different model bioassays. Further studies are in progress to optimize the operative parameters (i.e. working pH, laccase concentration, enzyme immobilization), in order to enhance the stability and the efficiency of the laccase-mediated system.