Synchronous removal of cadmium and ibuprofen by manganese oxidation denitrifying bacterium Zoogloea sp. ZY8: Performance and mechanism insights.

The coexistence of nitrate, heavy metals, and emerging organic contaminants in wastewater poses significant challenges to conventional biological treatment, particularly under carbon-limited conditions. This study isolated and identified a strain with high efficiency in both manganese (Mn) oxidation and denitrification, designated ZY8, and systematically evaluated its potential for simultaneous removal of multiple pollutants. Under optimal conditions (C/N = 2.0, pH = 6.5, Mn (II) = 20.0 mg L-1), strain ZY8 achieved 98.5% nitrate removal and 90.0% Mn (II) removal within 16 h. Mechanistic investigations revealed that Mn oxidation served as an alternative electron donor to drive denitrification, with comprehensive elucidation of electron transfer pathways and Mn transformation dynamics. Furthermore, strain ZY8 exhibited significant removal capacity toward combined ibuprofen (IBU) and cadmium (Cd (II)) contamination (86.9% and 84.6%, respectively), primarily attributed to the adsorption effects of extracellular polymeric substances (EPS) and biogenic manganese oxides. Critically, the biogenic manganese oxides generated during Mn oxidation served as multifunctional mediators facilitating electron transfer, adsorbing pollutants via surface complexation, and alleviating oxidative stress through ROS scavenging - thereby playing a central role in the coupled removal process. This study elucidates the mechanism of Mn oxidation-denitrification coupling and pollutant removal mediated by the ZY8 strain, and reveals its stress response characteristics under complex pollution conditions. These findings provide both a promising microbial resource and theoretical foundation for developing innovative bioremediation strategies targeting multi-pollutant wastewater treatment, offering practical implications for environmental management of industrial effluents containing coexisting heavy metals and organic contaminants.