Antibiofilm activity of biomolecules: gene expression study of bacterial isolates from brackish and fresh water biofouled membranes

Membrane biofouling is a common and emerging problem, where cells get cemented and create problems in industrial process. Frequent chemical cleaning used for the treatment of biofouled membrane shortens the membrane life time and creates ‘stress’ to existing microflora to trigger more exopolysaccharides production, which becomes the principle cause of biofouling. To understand safe and environmentally feasible antifouling strategies, key biofilm forming representative bacteria isolated from brackish and fresh water biofouled membranes were subjected to natural agents, such as vanillin (0.05–0.4 mg/mL) and salicylic acid (0.1–0.7 mg/mL). Salicylic acid (0.7 mg/mL) was found to be effective against only Pseudomonas group, whereas vanillin was remarkably potent against majority of the isolates because of structural mimicking with signalling autoinducer molecules. The present study showed that vanillin served as a good quorum quencher molecule as it inhibited 90% acyl homoserine lactones production at 0.3 mg/mL concentration in biosensor Chromobacterium violaceum CV026 strain and also inhibited 70% to > 90% biofilm formation in bacterial isolates. Biofilm formation and quorum sensing inhibition activities were validated by real-time quantitative PCR gene expression analysis in key representative membrane isolates. Vanillin served as antifouling natural agent towards broad spectrum community found on membranes