Unveiling the\nCoupling Mechanism between Central Carbon\nand Nitrogen Metabolism of Pseudomonas stutzeri: Polyhydroxyalkanoate-Enhanced Electron Supply for Denitrification

High nitrogen levels in drinking water sources pose a\npublic health\nthreat and have drawn significant attention. In situ high-efficiency\necological restoration technology using polyhydroxyalkanoates (PHAs)\ncan effectively enrich target microorganisms and enhance denitrification\nin water bodies. However, the mechanisms behind PHA-driven carbon\nmetabolism, nitrogen transformation, and electron transfer in denitrification\nremain unclear. This study investigated Pseudomonas\nstutzeri using sodium acetate (NaAc) or sodium 3-hydroxybutyrate\nas the sole carbon source. The PHA group achieved superior nitrogen\nremoval (171.44 mg/L N, 13.39 mg N/mg DNA) compared to the NaAc group\n(83.83 mg/L N, 7.98 mg N/mg DNA), driven by elevated NADH levels and\nan increased NADH/NAD+ ratio, facilitating electron transfer to denitrifying\nenzymes (i.e., Nap, Nir). The metabolic flux shifted, with the tricarboxylic\nacid (TCA) cycle decreasing 7.08-fold and the pentose phosphate pathway\n(PPP) increasing 2.53-fold, optimizing reducing equivalent production\nfor nitrogen assimilation and denitrification. A potential mechanism\nfor PHA-enhanced denitrification and new insights into how carbon\nsubstrates regulate microbial functions in denitrification were then\nproposed.