Bacterial bioaugmentation for paracetamol removal from water and sewage sludge. Genomic approaches to elucidate biodegradation pathway.

Lara-Moreno, A.; Vargas-Ordóñez, A.; Villaverde, J.; Madrid, F.; Carlier, Jorge; Santos, J. L.; Alonso, E.; Morillo, E.

http://hdl.handle.net/10400.1/26416

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Wastewater treatment plants (WWTPs) are recognized as significant contributors of paracetamol (APAP) into the environment due to their limited ability to degrade it. This study used a bioaugmentation strategy with Pseudomonas extremaustralis CSW01 and Stutzerimonas stutzeri CSW02 to achieve APAP biodegradation in solution in wide ranges of temperature (10-40 °C) and pH (5-9), reaching DT values < 1.5 h to degrade 500 mg L APAP. Bacterial strains also mineralized APAP in solution (<30 %), but when forming consortia with Mycolicibacterium aubagnense HPB1.1, mineralization significantly increased (up to 74 % and 58 % for CSW01 +HPB1.1 and CSW02 +HPB1.1, respectively), decreasing DT values to only 1 and 9 days. Despite the complete degradation of APAP and its high mineralization, residual toxicity throughout the process was observed. Three APAP metabolites were identified (4-aminophenol, hydroquinone and trans-2-hexenoic acid) that quickly disappeared, but residual toxicity remained, indicating the presence of other non-detected intermediates. CSW01 and CSW02 degraded also 100 % APAP (50 mg kg) adsorbed on sewage sludge, with DT values of only 0.7 and 0.3 days, respectively, but < 15 % APAP was mineralized. A genome-based analysis of CSW01 and CSW02 revealed that amidases, deaminases, hydroxylases, and dioxygenases enzymes were involved in APAP biodegradation, and a possible metabolic pathway was proposed.