[Identification and Characterization of a Hypothermic Alkaliphilic Aerobic Denitrifying Bacterium Pseudomonas monteilii Strain H97].

Low temperatures and high pH generally inhibit bio-denitrification. Thus, it is important to explore psychrotrophic and alkali-resistant microorganisms for nitrogen degradation. This study mainly focused on the identification of an alkaliphilic strain and preliminary exploration of its denitrification characteristics. Based on morphological observations, phospholipid fatty acids and 16S rRNA gene sequence analysis, strain H97, which was isolated from the winter paddy field in Guizhou province, was identified as Pseudomonas monteilii. Till date, there were few reports about the denitrification characteristics of Pseudomonas monteilii. The effects of environmental factors such as temperature, inoculation quantity, C/N ratio, initial pH, and carbon source were investigated using simulated wastewater. The optimum conditions for nitrate and total nitrogen removal by H97 were: inoculum size 1.5×106 CFU·(100 mL)-1; initial pH 9.0; C/N=15; 15℃; and sodium succinate as the carbon source. The nitrate and total nitrogen removal efficiencies were 97.69% and 96.32%, respectively, at optimum conditions with an initial nitrate nitrogen concentration of 50.0 mg·L-1. The temperature experiments indicated that the optimal temperature for highest nitrogen removal efficiency was 15℃, and that the strain H97 could survive in a wide range of 15-40℃. Additionally, the nitrate and total nitrogen efficiencies at the initial pH value of 7.0-11.0 were 91.21% and 79.10%, respectively, and the denitrification capacity then decreased to 64.75% at the initial pH 12.0. These results indicated that strain H97 showed cold and alkali resistance, which suggests an application potential for the treatment of alkaline nitrogen polluted water in the southern winter.

[Heterotrophic Nitrification and Aerobic Denitrification of the Hypothermia Aerobic Denitrification Bacterium: Arthrobacter arilaitensis].

High concentrations of ammonium, nitrate and nitrite nitrogen were employed to clarify the abilities of heterotrophic nitrification and aerobic denitrification of Arthrobacter arilaitensis strain Y-10. Meanwhile, by means of inoculating the strain suspension into the mixed ammonium and nitrate, ammonium and nitrite nitrogen simulated wastewater, we studied the simultaneous nitrification and denitrification ability of Arthrobacter arilaitensis strain Y-10. In addition, cell optical density was assayed in each nitrogen removal process to analyze the relationship of cell growth and nitrogen removal efficiency. The results showed that the hypothermia denitrification strain Arthrobacter arilaitensis Y-10 exhibited high nitrogen removal efficiency during heterotrophic nitrification and aerobic denitrification. The ammonium, nitrate and nitrite removal rates were 65.0%, 100% and 61.2% respectively when strain Y-10 was cultivated for 4 d at 15°C with initial ammonium, nitrate and nitrite nitrogen concentrations of 208.43 mg · L⁻¹, 201.16 mg · L⁻¹ and 194.33 mg · L⁻¹ and initial pH of 7.2. Nitrite nitrogen could only be accumulated in the medium containing nitrate nitrogen during heterotrophic nitrification and aerobic denitrification process. Additionally, the ammonium nitrogen was mainly removed in the inorganic nitrogen mixed synthetic wastewater. In short, Arthrobacter arilaitensis Y-10 could conduct nitrification and denitrification effectively under aerobic condition and the ammonium nitrogen removal rate was more than 80.0% in the inorganic nitrogen mixed synthetic wastewater.