Pseudomonas sp. MSW2-Mediated Biodegradation of Pharmaceutical Micropollutants: Experimental and In Silico Investigations

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Abstract
Environmental contamination from pharmaceutical and personal care products is a growing concern due to their widespread use. This study was aimed to investigate the biodegradation of acetaminophen and hydroxychloroquine alongside computational analysis (DFT calculations and molecular docking). The acetaminophen and hydroxychloroquine-tolerant strain was isolated from pharma industrial wastewater and identified as Pseudomonas sp. MSW 2 (GenBank: PP800223.1) based on morphological, biochemical, as well as DNA barcoding method. Based on the UV–VIS spectroscopy and HPLC data it was confirmed that Pseudomonas sp. MSW 2 degrades 1000 ppm of acetaminophen by 95% within 3 days and 50 ppm of hydroxychloroquine by 95% within 5 days, following first-order degradation kinetic models with rate constants of 0.65 d−1 and 0.457 d−1, respectively. Based on HRMS and 1H NMR spectroscopy data, 1,4-benzoquinone and 7-chloro-4-quinolinamine were identified as degradative product of acetaminophen and hydroxychloroquine, respectively. The HOMO–LUMO energy gap (ΔEg) for acetaminophen,1,4 benzoquinone, hydroxychloroquine and 7-chloro-4-quinolinamine is 5.35 eV, 2.38 eV, 4.45 eV, and 4.55 eV, respectively. Data suggests that 1,4 benzoquinone has lower stability and higher reactivity compared to the acetaminophen. Whereas in case of hydroxychloroquine degradative product (7-chloro-4-quinolinamine), negligible changes were observed in the reactivity. Molecular docking simulations predicted a strong binding affinity (-26 kcal/mol) between acetaminophen and the amidase (PDB ID 2UXY) enzyme from P. aeruginosa, facilitated by hydrogen bonding. This study gives new insights in the bioremediation process, using the DFT calculations to theoretically document the reactivity and stability of pollutant as well as their biodegradative metabolites.

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