Epsilon Archive for Student Projects

Abstract

Pharmaceutical contamination in source-separated urine is a potential barrier to its safe recycling as fertiliser. Enzymatic oxidation using laccase could provide a mild treatment option to remove pharmaceuticals while preserving nutrients in urine.
This study investigated whether laccase from the fungus Trametes versicolor (Turkey tail) could transform selected pharmaceuticals in real pooled human urine and whether the natural redox mediators syringaldehyde and vanillin could enhance treatment. A series of preparatory experiments examined the effects of pH, temperature, urine concentration, acid type, and oxygen supply on laccase activity. Based on these experiments, a mixture of 19 pharmaceuticals was treated with laccase at pH 4.5 and 50 °C under continuous aeration for 24 h, with and without mediators. Changes in parent-compound concentrations were measured by UPLC-MS/MS.
Laccase remained active in unconcentrated urine, although activity declined with increasing urine concentration and during incubation at 50 °C. Continuous aeration was required to prevent oxygen depletion. Sulfamethoxazole showed the clearest treatment response, with a 46% decrease after 24 h, compared with negligible change in the untreated control. Diclofenac showed apparent removal of 50% though control variability was substantial. Three additional compounds (losartan, irbesartan, and furosemide) showed apparent decreases, but anomalous changes in the corresponding controls limited interpretation. Neither syringaldehyde nor vanillin consistently improved pharmaceutical transformation compared with laccase alone.
These findings provide proof-of-concept that laccase treatment can remain active and transform selected pharmaceuticals in real source-separated urine under practically relevant conditions.