Simultaneous phenanthrene biodegradation and carbon mineralization by a denitrifying bioemulsifier-producing Pseudomonas stutzeri YWX-1 in almost-anoxic water environments.

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.