Batch studies on the biodegradation of paracetamol and 1,4-hydroquinone by novel bacterial strains isolated from extreme environmental samples and the identification of candidate catabolic genes

The emerging pollutant paracetamol (APAP) is one of the most prescribed drugs worldwide. In addition, APAP and its main metabolites, namely, 4-aminophenol (4-AP), hydroquinone (H2Q), benzoquinone (BQ), and 2,5-dihydroxy-1,4-benzoquinone (2,5-OH-BQ), among others, are frequently detected in wastewater treatment plants (WWTPs) influents, effluents, and the environment. Thus, continuous release into the environment, especially aquatic environments, is a source of general concern. Six APAP-degrading bacterial strains were isolated from two mine samples from the Iberian Pyrite Belt (Lousal and Poderosa mines). Mycolicibacterium aubagnense HPB1.1, which was isolated using enrichment cultures from the Poderosa mine sample in the presence of H2Q as the sole carbon source, also showed APAP biodegrading capabilities. Pure cultures of this strain degraded 34.3 mg L−1 of APAP in 5 days and 9.4 mg L−1 of H2Q in 4 days. Interestingly, BQ and 2,5-OH-BQ were detected as metabolites resulting from H2Q abiotic degradation, but these compounds were removed in the strain’s cultures. Furthermore, M. aubagnense HPB1.1 whole-genome was sequenced, and its encoded proteins were aligned with enzymes of APAP-degrading bacteria recovered from databases and literature aiming to identify candidate catabolic genes. Putative amidases, deaminases, hydroxylases, and dioxygenases, responsible for the degradation of APAP by the HPB1.1 strain, were identified by similarity, corroborating its ability to transform APAP and its intermediate metabolite H2Q into less toxic metabolic compounds due to their capacity to break the aromatic ring of these molecules.