Isolation, identification and nitrate reduction ability of a salt-tolerant strain of Zobellella sp.

Abstract:

[Background] Aerobic denitrification is carried out under aerobic conditions, so that nitrification and denitrification can occur at the same time in the same reactor, which is the most competitive technology for nitrogen removal from wastewater. Mangrove wetlands are rich in microbial resources and a large number of aerobic denitrifying microorganisms are distributed. [Objective] In order to understand the denitrification mechanism of salt-tolerant microorganisms and provide a theoretical basis for the engineering practice of biological denitrification of salt-bearing wastewater, a salt-tolerant aerobic bacteria A63 was isolated from the mangrove wetland and its nitrate reduction ability was analyzed. [Methods] The species were identified by morphological characteristics and 16S rRNA gene sequencing. The nitrate reduction ability of the strain under different environmental factors was determined by single factor experiment, and its denitrification performance was optimized. [Results] It was preliminarily determined that the strain belonged to the Zobellella sp. The strain can carry out denitrification and dissimilatory nitrate reduction to ammonium (DNRA) action in the range of salinity 0%?10%, pH 5.0?10.0 and temperature 20?40 °C. The optimum growth carbon source is sodium citrate (1.2 g/L), and the optimum salinity 3.0%, the pH is 7.0?7.5, the temperature is 30?35 °C and C/N is 10. Under the optimum denitrification condition, the strain could reduce 208.8 mg/l NO3?-N to 0 in the medium within 12 hours, and only a small amount of ammonium nitrogen was produced. There was no accumulation of nitrite nitrogen, and the denitrification rate was as high as 99%. Furthermore, the strain had a significant effect on DNRA in adverse habitats such as high salinity, low C/N ratio, weak acidity and low temperature. [Conclusion] The strain A63 has a wide range of growth and remarkable nitrogen removal efficiency, so it is suitable for the treatment of mariculture wastewater. The present study lays a foundation for the development of high efficiency biological nitrogen removal process for salty wastewater in the future, and is of great significance to deepen the understanding of nitrogen transformation law and enrich the theory of biological nitrogen removal.