Inhibiting quorum sensing pathways to mitigate seawater desalination RO membrane biofouling

• Quorum sensing inhibitors for membrane biofouling prevention were investigated.
• All biofouling bacteria examined secreted autoinducer I quorum sensing molecule.
• The quorum sensing inhibitor, vanillin reduced EPS on membrane surface by > 40%.

Bacterial biofilm formation, the main cause of membrane biofouling, is a crucial issue for membrane separation. Biofilm production is regulated by quorum sensing (QS) systems where bacteria secrete auto-inducers to communicate with neighboring bacteria. This research identified that several marine bacteria isolated from a desalination plant produced a low molecular weight auto-inducer 1 (AI-1) signaling molecule. AI-1 production in the mixed culture of the four different biofilm-forming marine bacteria was greater than in individual bacterial cultures. The QS inhibiting compounds, vanillin and cinnamaldehyde at 1200 mg/L significantly reduced biofilm formed by these marine bacteria by more than 79% and 70%, respectively in a microtiter plate assay. Anti-biofilm capabilities of vanillin and cinnamaldehyde were further assessed in a reverse osmosis membrane bio-monitoring system using mixed bacterial cultures and native uncultured bacterial communities in natural seawater. Confocal microscopy showed vanillin (1200 mg/L) significantly reduced biofilm extracellular polysaccharides and dead cells on the membrane surface (> 40%, > 20%). These results indicate that QS inhibitors have the potential to remediate membrane biofouling.