Biodegradation of Paracetamol by Some Gram-Positive Bacterial Isolates

Bacterial isolates with the capacity to remove paracetamol were selected from an activated sludge sample collected in an oxidation ditch of a wastewater treatment plant. Among these, twelve bacterial isolates were selected according to their capacity to grow in the presence of paracetamol. They were identified using the colony morphotype procedure and by 16S rRNA gene sequencing analysis, but only four of them showed the ability to utilise paracetamol as the sole carbon source in the presence of a nitrogen supply. Those four bacterial isolates were assigned to species of the genera Bacillus, [Brevibacterium], Corynebacterium and Enterococcus. Bacterial isolates were cultured in liquid mineral salt medium (MSM) spiked with 200 mg/L of paracetamol at 28 °C in the dark. In cultures inoculated with [Brevibacterium] frigoritolerans, Corynebacterium nuruki and Enterococcus faecium, removal of 97 ± 4%, 97 ± 6% and 86.9 ± 0.8% of paracetamol at 200 mg/L were obtained, respectively, while in the presence of a species belonging to Bacillus cereus group removal of the drug below the limits of detection was attained with evidence of mineralisation, after 144 h of incubation. During the degradation process, the metabolites 4-aminophenol, hydroquinone and 2-hexenoic acid were detected. As far as we know, these species are herein first-time described as paracetamol degraders.