Membrane biofouling is widely acknowledged as the most frequent adverse event in wastewater treatment systems resulting in significant loss of treatment efficiency and economy. Different strategies including physical cleaning and use of antimicrobial chemicals or antibiotics have been tried for reducing membrane biofouling. Such traditional practices are aimed to eradicate biofilms or kill the bacteria involved, but the greater efficacy in membrane performance would be achieved by inhibiting biofouling without interfering with bacterial growth. As a result, the search for environmental friendly non-antibiotic antifouling strategies has received much greater attention among scientific community. The use of quorum quenching natural compounds and enzymes will be a potential approach for control of membrane biofouling. This approach has previously proven useful in diseases and membrane biofouling control by triggering the expression of desired phenotypes. In view of this, the present review is provided to give the updated information on quorum quenching compounds and elucidate the significance of quorum sensing inhibition in control of membrane biofouling.

High-quality drinking water is obtained using membrane technology. Biofilm development lowers filtration efficacy and eventually membranes must be replaced. In natural environments, a micro-organism produces different kinds of quorum sensing (QS) molecules resulting in biofilm formation and biofouling. Biological fouling is a major problem in desalination and water purification plants. Biofilm formation can be reduced using eco-friendly substances in the drinking water system based on quorum sensing inhibition (QSI). Vanillin (4-hydroxy-3-methoxybenzaldehyde), a well-known food flavoring agent, was studied for its QSI property against different individual acyl homoserine lactone (AHL) molecules using bio indicator strains. Vanillin showed significant inhibition in short-chain [C4-HSL (69%) and 3-Oxo-C8-HSL (59.8%)] and long-chain AHL molecules. QSI activity was tested on a reverse osmosis (RO) membrane biofilm bacteria Aeromonas hydrophila. Biofilm formation was inhibited up to 46.3% on polystyrene surface. Results suggested that Vanillin could be used as a potential QSI compound that reduces the biofilm formation on RO membranes.

Membrane biofouling remains a severe problem to be addressed in wastewater treatment systems affecting reactor performance and economy. The finding that many wastewater bacteria rely onN-acyl homoserine lactone-mediated quorum sensing to synchronize their activities essential for biofilm formations; the quenching bacterial quorum sensing suggests a promising approach for control of membrane biofouling. A variety of quorum quenching compounds of both synthetic and natural origin have been identified and found effective in inhibition of membrane biofouling with much less environmental impact than traditional antimicrobials. Work over the past few years has demonstrated that enzymatic quorum quenching mechanisms are widely conserved in several prokaryotic organisms and can be utilized as a potent tool for inhibition of membrane biofouling. Such naturally occurring bacterial quorum quenching mechanisms also play important roles in microbe-microbe interactions and have been used to develop sustainable nonantibiotic antifouling strategies. Advances in membrane fabrication and bacteria entrapment techniques have allowed the implication of such quorum quenching bacteria for better design of membrane bioreactor with improved antibiofouling efficacies. In view of this, the present paper is designed to review and discuss the recent developments in control of membrane biofouling with special emphasis on quorum quenching bacteria that are applied in membrane bioreactors.

Biofouling due to biofilm formation on surfaces is recognized as the most serious problem in membrane processes. Quorum sensing (QS) mechanisms are mediated by small diffusible molecules called autoinduzers, usually N-acyl homoserine lactones (AHLs) in Gram-negative bacteria and are involved in the formation of biofilm. In the current study, the AHL-degrading enzyme, Acylase I (Porcine kidney) was tested to inhibit biofilm formation by environmental strains of bacteria. Preliminary studies with pure AHL revealed that there was considerable degradation of the AHL with 5–60 μg/mL of Acylase I, as indicated in the thin-layer chromatography (TLC)-Biosensor strain method. The applicability of Acylase I in the prevention of biofilm formation was tested on three different surfaces. Acylase I reduced biofilm formation by Aeromonas hydrophila and Pseudomonas putida on borosilicate (36 and 23%), polystyrene (60 and 73%), and the reverse osmosis (RO) membrane (20 and 24%). This is the first report on the potential of Acylase I to reduce of biofilm formation by environmental strains of biofouling bacteria. Further experiments are warranted to gain a better understanding on the practicality of this technology for biofouling control in membrane systems.

The formation of biofilm in a membrane bioreactor depends on the production of various signaling molecules like N-acyl homoserine lactones (AHLs). In the present study, a total of 200 bacterial strains were isolated from membrane bioreactor activated sludge and screened for AHLs production using two biosensor systems, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens A136. A correlation between AHLs production and biofilm formation has been made among screened AHLs producing strains. The 16S rRNA gene sequence analysis revealed the dominance of Aeromonas and Enterobacter sp. in AHLs production; however few a species of Serratia, Leclercia, Pseudomonas, Klebsiella, Raoultella and Citrobacter were also identified. The chromatographic characterization of sludge extract showed the presence of a broad range of quorum sensing signal molecules. Further identification of sludge AHLs by thin layer chromatography bioassay and high performance liquid chromatography confirms the presence of C4-HSL, C6-HSL, C8-HSL, 3-oxo-C8-HSL, C10-HSL, C12-HSL, 3-oxo-C12-HSL and C14-HSL. The occurrence of AHLs in sludge extract and dominance of Aeromonas and Enterobacter sp. in activated sludge suggests the key role of these bacterial strains in AHLs production and thereby membrane fouling.