Biodegradation of paracetamol by Bacillus sp. kinetics and metabolite profiling

The over-usage of paracetamol (PCT) has increased its concentration in aquatic environments, indicating the inefficiency of wastewater treatment plants (WWTPs) in PCT removal. Its accumulation, along with its metabolites, poses risks to aquatic ecosystems and organisms relying on these water sources. This study hypothesized that bacteria isolated from gold mine tailings possess the ability to biodegrade PCT effectively. Six bacterial species, Bacillus clausii, Bacillus niacini, Bacillus thuringiensis, Bacillus licheniformis, Staphylococcus capitis, and Rhizobium flavum, were isolated and identified via 16S rRNA sequencing. Their PCT degradation capabilities (100–500 mg/L) were assessed using High-performance liquid chromatography (HPLC), while metabolites were identified using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). B. clausii achieved >95% degradation at 100 mg/L but exhibited reduced efficiency (<45%) at higher concentrations, while B. niacini, B. thuringiensis, and B. licheniformis achieved >75% degradation for 200–500 mg/L PCT. Kinetic analysis revealed predominantly zero-order kinetics, while B. clausii followed first and second-order kinetics for 200 and 500 mg/L PCT, respectively. FTIR analysis indicated PCT degradation by Bacillus strains, with no changes observed in abiotic controls. The biodegradation pathway led to the formation of value-added metabolites, including 2-(2,6-diisopropylphenyl)-5-hydroxyisoindole-1,3-dione, Oleoyl-L-carnitine, tetrahydropalmatine, minocycline, tentoxin, 4-nitrophenol, and pyrocatechol, which exhibit potential pharmaceutical and cosmetic applications. The recovery, characterization, and pharmacological properties of these compounds are significant for understanding their potential and application. This study demonstrated the degradation potential of extremophilic bacteria PCT and introduced a novel pathway for converting pharmaceutical pollutants into valuable bioactive compounds, promoting environmental sustainability and resource recovery.