Optimal dosing regimen of nitric oxide donor compounds for the reduction of Pseudomonas aeruginosa biofilm and isolates from wastewater membranes

Membrane fouling by bacterial biofilms remains a key challenge for membrane-based water purification systems. Here, the optimal biofilm dispersal potential of three nitric oxide (NO) donor compounds, viz. sodium nitroprusside, 6-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-hexanamine (MAHMA NONOate) and 1-(hydroxy-NNO-azoxy)-L-proline, disodium salt, was investigated using Pseudomonas aeruginosa PAO1 as a model organism. Dispersal was quantitatively assessed by confocal microscopy [bacterial cells and the components of the extracellular polymeric substances (EPS) (polysaccharides and extracellular DNA)] and colony-forming unit counts. The three NO donor compounds had different optimal exposure times and concentrations, with MAHMA NONOate being the optimal NO donor compound. Biofilm dispersal correlated with a reduction in both bacterial cells and EPS. MAHMA NONOate also reduced single species biofilms formed by bacteria isolated from industrial membrane bioreactor and reverse osmosis membranes, as well as in isolates combined to generate mixed species biofilms. The data present strong evidence for the application of these NO donor compounds for prevention of biofouling in an industrial setting.