Characters of a nitrobacter enrichment culture from a freshwater aquaculture pond

• Main Authors: Mengying He, Ying Xiong, Kai Cheng
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2021-01-01
• Series: Biotechnology & Biotechnological Equipment
• Subjects: nitrite-oxidizing bacteria; nob; growth; brackish water; shrimp pond
• Online Access: http://dx.doi.org/10.1080/13102818.2021.1974944

To isolate nitrite-oxidizing bacteria to control the nitrite concentration in freshwater aquaculture systems, a Nitrobacter enrichment culture was obtained from a freshwater shrimp pond using a continuous enrichment and gradient dilution method. There was only one species of Nitrobacter in the enrichment culture, with an abundance of more than 99%. The Nitrobacter strain was identified as Nitrobacter vulgaris XY-12 on the basis of its 16S rRNA gene and NxrA gene sequences. The effects of pH, temperature, salinity and nitrate on the nitrification activity of the enrichment culture were examined, and its ability to remove nitrite in aquaculture water was also tested. The results showed that the optimum pH for the nitrite-oxidation activity of the enrichment culture was 7.5, the optimum temperature range was 27 °C–30 °C, the optimum salinity was 0.38%, the half maximal inhibitory concentration (IC50) of NO3−–N was 400 mg L−1, and the optimum concentration of NO2−–N was 200 mg L−1. In optimum conditions, the maximum NO2−–N removal rate afforded by the enrichment was 1.62 mg L−1 h−1, and the minimum doubling time was 12 ± 2 h. Moreover, XY-12 could multiply in field aquaculture water, and the maximum NO2−–N removal rate was 0.15 mg L−1 h−1. These results indicated that the enrichment had good application prospects in aquaculture waters.