Exploring the nitrogen removal capacity of Klebsiella aerogenes B23 isolated from shrimp farm wastewater: heterotrophic nitrification and aerobic denitrification.

Heterotrophic nitrification and aerobic denitrification (HN-AD) bacteria are essential for aquaculture wastewater treatment to ensure product quality and environmental sustainability. Klebsiella aerogenes strain B23 was isolated from shrimp farm wastewater and identified based on phenotypic and phylogenetic characteristics. The strain demonstrated high removal efficiency and the maximum removal rates for ammonia (96.48%; 6.18 mg/L/h), nitrate (93.48%; 4.45 mg/L/h), and nitrite (90.92%; 2.38 mg/L/h). In wastewater from a shrimp farm, B23 reached a nitrate removal efficiency of 92.18% after 36 h. The expression of denitrifying genes (norV, norW, narJ, and narR) confirmed the HN-AD ability of strain B23. Single-factor experiments revealed that the optimal conditions for nitrate removal were a nitrate concentration of 5 mg/L, sucrose as a carbon source, temperature of 30 °C, pH of 7.5, rotation rate of 120 rpm, and salinity of 5‰. These findings demonstrate that strain B23 is a candidate for nitrogen removal in aquaculture wastewater treatment. [ABSTRACT FROM AUTHOR]