Ammonia nitrogen degrading characteristics by the novel strain Alcaligenes sp. TD-94 and regulation mechanism of POD gene

Heterotrophic nitrification-aerobic denitrification bacteria have attracted more and more attention due to their high tolerance to ammonia nitrogen, efficient nitrogen removal capacity, and strong pH adaptability. This experiment studied the optimal conditions for the degradation of ammonia nitrogen by the heterotrophic nitrification-aerobic denitrification strain Alcaligenes sp. TD-94. Based on gene identification results, the metabolic pathway of TD-94 for degrading ammonia nitrogen was inferred. The key enzyme pyruvic oxime dioxygenase (POD) in the heterotrophic nitrification process was purified, and its catalytic properties were studied. The results showed that the denitrification performance of Alcaligenes sp. TD-94 was optimal when the carbon source was sodium acetate, the C/N ratio was 10, the pH was 7.0, the inoculation amount was 10%, and the temperature was 28–37 °C. The pathway of strain TD-94 is NH₄⁺ - NH₂OH - NO₂⁻ - NO - N₂O - N₂. In the experiment, POD was successfully expressed at 28 °C. After purification, it remained stably expressed, and enzymatic reaction verification showed good nitrite generation. The protein structure of POD was predicted, and it was highly similar to the known aldolase structure in the PBD database, and the predicted amino acid sequence of POD from positions 32 to 210 was detected as the aldolase domain.