Characterization and performance of efficient heterotrophic nitrification and aerobic denitrification by Comamonas testosteroni HR5 under low temperature and high alkalinity

A newly isolated Comamonas testosteroni strain, HR5, exhibited efficient nitrogen removal capacities at low temperature and high alkalinity. HR5 efficiently removed nitrate nitrogen (removal efficiency >= 95 %) at C/N = 12-15, pH 6-11, and 5-25 degrees C. Furthermore, the removal efficiency of total dissolved nitrogen (TDN) for ammonia, nitrate, and nitrite as the sole nitrogen source system reached 97.90 +/- 0.02 %, 95.16 +/- 0.01 %, and 99.95 +/- 0.00 %, respectively; the removal efficiency for the mixed nitrogen system was >91 % at 5 degrees C and pH 10. Nitrogen balance indicated that HR5 converted initial nitrogen into gaseous products (20.87-77.13 %) and biological nitrogen (19.58-75.65 %), with the percentage of gaseous N increasing as the temperature increased. Furthermore, typical cold-resistance genes (cspA, infB, and rbfA) and alkalinity-resistance genes (Pha and Trk) were involved. These results provide a reference for practical applications of Comamonas testosteroni that involve low temperature and high alkalinity.