Simultaneous phenanthrene biodegradation and carbon mineralization by a denitrifying bioemulsifier-producing...

Polycyclic aromatic hydrocarbons (PAHs) accumulation in water environments from petroleum development and transportation poses biosecurity risks and increases CO₂ emissions, yet the bioremediation processes and related CO₂ fate in oxygen-deprived deep water receive little attention. In this study, the almost-anoxic phenanthrene biodegradation and associated CO₂ metabolism by a denitrifying Pseudomonas stutzeri strain YWX-1 were detected. The results showed that 41.52% of 100 mg L^-1 phenanthrene was biodegraded via the dual pathway of oxygenation and denitrification within 21 days with the consumption of 22.03 mM nitrate, wherein the biotransformation was revealed by GC-MS, genome, and RT-qPCR analysis. SEM-EDS, FT-IR, and XRD analysis suggested that CO₂ was converted into 61.26 mg CaCO₃ crystals within 72 h by strain YWX-1 with the action of carbonic anhydrase, reducing net CO₂ emission. Furthermore, the glycoprotein-bioemulsifier produced by strain YWX-1 was characterized by FT-IR and 3D-EEM, and recognized to enhance the water solubility of phenanthrene from 0.6 to 10.76 mg L^-1, as well as expand the carbon mineralization to 2.02 times that of the control group. On this basis, the putative almost-anoxic phenanthrene biotransformation and CO₂ mineralization strategies mediated by strain YWX-1 were proposed. This study would provide novel insights into the synchronous remediation of PAH pollutants and CO₂ in oxygen-deprived aquatic systems, offering a sustainable bio-driven strategy to environmental protection and carbon neutrality.