Engineering Psl Polysaccharide Biofilms as Living Bioflocculants for Dye Decolorization

Decolorization remains a major challenge in the treatment of dye-containing wastewater. Here, we engineered Escherichia coli with a chromosomally integrated minimal Psl polysaccharide synthesis operon, pslA-G, to create a Psl biofilm-based living bioflocculant enabling autonomous dye capture, sedimentation, and controllable recovery. The engineered bioflocculant exhibited rapid self-flocculation, achieving approximately 85% sedimentation within 8 h. The bioflocculant mediated the removal of Reactive Red 24, Acid Orange 7, and Congo red in a dye-dependent manner, achieving its highest removal efficiency of approximately 90% for Congo red. Importantly, dye-loaded aggregates could be disassembled via PslG-triggered Psl polysaccharide hydrolysis, enabling controlled dye release. This work establishes a proof-of-concept living bioflocculation approach that integrates capture, sedimentation, and recovery for potential dye wastewater treatment.