Biological characteristics of a denitrifying phosphorus-accumulating bacterium

To isolate highly efficient denitrifying phosphorus-accumulating bacteria (DPAB) for synchronous nitrogen and phosphorus removal, it is necessary to understand their biological characteristics. Using denitrification screening, polyphosphate (poly-P) and poly-beta-hydroxybutyrate (PHB) granule staining, nitrate reduction, nitrate reduction producing N-2, and phosphorus uptake tests, a strain of efficient DPAB was isolated. This strain was identified as Thauera by 16S rDNA sequencing and physiological-biochemical analyses, and named N11. The growth of the strain N11 was obviously affected by nitrogen source, carbon source, temperature, and pH (p < 0.05 or p < 0.01). LB was considered the suited nutrient removal medium and the optimum pH and temperature were 8 and 35 degrees C, respectively. Under the optimal culture conditions for 32 h, the bacteria could consistently keep active, OD600 maintained at approximately 1.8, and the count was 1.826 x 10(13)-3.218 x 10(13) cfu/mL. With anaerobic-aerobic training in synthetic wastewater, the polyhydroxyalkanoate (PHA) content in cells increased from 22.8 mg/L to 150.6 mg/L (under anaerobic conditions, 12 h), and then gradually decreased to 20.4 mg/L (under aerobic conditions, 24 h). The phosphate (PO43 -P) concentration in culture supernatants increased from 4 mg/L to 20.8 mg/L (under anaerobic conditions, 12 h), and then gradually decreased to 3.08 mg/L (under aerobic conditions, 24 h), and the phosphorus removal rate was 80.38%. The nitrate-nitrogen (NO3 -N) concentration decreased from 75.45 mg/L to 7.12 mg/L. Nitrite-nitrogen (NO2 -N) was at a low concentration (<= 1.29 mg/L). The denitrification rate was 89.96%. This study describes a novel strain of DPAB and the optimal conditions for nitrogen and phosphorus removal by this strain. (C) 2015 Elsevier B.V. All rights reserved.