Biodegradation characteristics of acetaminophen by Delftia sp. PY-12: Performance, degradative kinetics, and pathway

Acetaminophen (APAP) is widely used for its antipyretic properties and is commonly found in wastewater, potentially threatening aquatic ecosystems. Microbial degradation has been proven effective in removing APAP. However, strains capable of efficiently degrading APAP are rare, and the research on the biodegradation kinetics of APAP is insufficient. In this study, a novel APAP-degrading strain, identified as Delftia sp. PY-12 by morphological characterization and 16S rRNA gene sequencing, was isolated from activated sludge. Experimental conditions were optimized using the Box-Behnken response surface design, revealing that PY-12 degraded 100 mg/L APAP under pH 7.11, 30℃, and 163 rpm within 24 h, outperforming most other strains. Comparative analysis of substrate inhibition models shows that the Aiba and Tiesser were most suitable for the substrate inhibition characteristics of PY-12. The models indicate that PY-12 can still degrade APAP even at concentrations of 446.919 mg/L and 554.215 mg/L. Through potential enzyme activity measurements, the degradation pathway of APAP by PY-12 was determined. APAP is first converted by amidohydrolase into 4-aminophenol (4-AP) and then converted by deaminase into hydroquinone (HQ), which is further converted by hydroquinone 1,2-dioxygenase to form 4-hydroxymuconic semialdehyde, ultimately entering the TCA cycle. This study revealed the potential application value of PY-12 in APAP degradation, which could be a strong candidate strain for microbial bioremediation of APAP pollution in environmental remediation.