Biodegradation of organic micropollutants dibutyl phthalate and bisphenol A by fungi
Sammanfattning: Fungi represent a promising and relatively untapped resource in regard to the bioremediation of micropollutants. Degradation efficiencies of the ubiquitous endocrine disrupting chemicals dibutyl phthalate (DBP) and bisphenol A (BPA) by selected fungal strains with different ecophysiologies were determined via ultra performance liquid chromatography (UPLC). The micropollutants were almost completely (about 100% of the initial concentration) removed by all fungi except the wetland isolate Stachybotrys chlorohalonata. Biotransformation of micropollutants tested was observed, but the degree of transformation varied between individual strains. Strongest biocatalytic DBP degradation was observed for the white-rot fungus Stropharia rugosoannulata followed by the aquatic Clavariopsis aquatica, implying wide-spread presence of DBP degraders in the environment. Contribution of P450 monooxygenase(s) to DBP degradation in Stropharia rugosoannulata and Clavariopsis aquatica, followed by Stachybotrys chlorohalonata was indicated by caused inhibition of micropollutant degradation through the cytochrome P450 inhibitor piperonyl butoxide. Nevertheless, biosorption dominated removal of pollutants for the other fungi. S. rugosoannulata also efficiently biotransformed BPA, seemingly involving cytochrome P450 catalyzed reactions, whereas biosorption was a less important removal process. By contrast, biosorption was the only BPA removal process operative in S. chlorohalonata. Activity of extracellular lignin-modifying enzymes was quantified by spectrophotometric ,′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) ABTS assays, and laccase activity detected inS. rugosoannulata may have contributed to BPA removal by this strain. Elucidation of DBP degradationmetabolites of T. porosum, S. rugosoannulata and S. chlorohalonata confirmed oxidative and hydrolytic biotransformation steps, in line with literature data. Monobutyl phthalate and phthalic acid were identified as prominent intermediates in all investigated strains and S. rugosoannulata, respectively. Keywords micropollutant, dibutyl phthalate, bisphenol A, fungi, biodegradation, biosorption, endocrine disrupting chemical.
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