Metagenomic insights into carbon-nitrogen metabolism of heterotrophic nitrification-aerobic denitrification bacteria...

Nitrogen pollution poses a critical threat to aquatic ecosystems worldwide, and biodegradable polymers have recently gained increasing attention as effective carbon sources to enhance biological nitrogen removal. This study systematically evaluated the nitrogen removal performance of heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria using various biodegradable polymers. Among them, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV, 100 kDa) showed promising performance, with a sustained carbon release rate of 2.04 mg g^-1·h^-1 and a total nitrogen (TN) removal rate of 1.82 mg L^-1·h^-1. Metagenomic analysis indicated that Acidovorax, a key degrader of PHBV granules, played a dominant role in the denitrification process with a relative abundance of 33.89 %, contributing 31.8 % and 48.23 % to carbon and nitrogen metabolism, respectively. In the PHBV (100 kDa) system, Stappia was identified as the predominant genus, accounting for 52.35 % of the microbial community and contributing 57.87 % and 64.52 % to carbon and nitrogen metabolism, respectively. Functional gene profiling further suggested that PHBV significantly upregulated key nitrogen metabolism genes and enzymes, including nirK, norB, and nosZ. These results provide valuable insights into microbial mechanisms supporting polymer-based nitrogen removal and highlight the potential of PHBV as a sustainable carbon source in wastewater treatment.