[Identification and Characterization of a Hypothermic Alkaliphilic Aerobic Denitrifying Bacterium Pseudomonas...

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.