Simultaneous nitrification and denitrification by a novel isolated Pseudomonas sp. JQ-H3 using polycaprolactone as carbon source

•Pseudomonas sp. exhibited the HN-AD ability using PCL as a sole carbon source.•The amoA, napA, nirS, cnorB and nosZ genes were successfully expressed.•The weight loss of PCL films reached 94.03% after 60-days degradation.•The increase in PCL concentrations led to a decrease in nitrogen removal rate. The novel isolated strain JQ-H3 exhibited heterotrophic nitrification-aerobic denitrification (HN-AD) ability using poly (ε-caprolactone) (PCL) as a sole carbon source under aerobic conditions. This was the first time that a PCL-degrading bacterium was characterized to be with capability of nitrifying and denitrifying performances. Strain JQ-H3 removed approximately 95.40% of NH4+-N (102.40 mg/L), about 91.1% of NO3−-N (99.01 mg/L), with the maximum specific removal rates of 0.308 mg NH4+-N/mg DCW/h and 0.220 mg NO3−-N/mg DCW/h, respectively. The functional genes amoA, napA, nirS, cnorB, and nosZ were successfully expressed during the nitrogen removal process. An increasing PCL concentrations caused a decline in cell growth and nitrogen removal efficiency, which was attributed to the decrease in the rate of the PCL hydrolysis and the amount of dissolved organic carbon (DOC) release. These results demonstrated the strain as an ideal candidate for nitrogen removal from wastewater by using PCL as carbon source.