Rosmarinus officinalis Might be Exploited as a Natural Antifouling Agent: A Potentially Promising Strategy for Curbing Membrane Biofouling

Membrane biofouling is the coverage of membrane surfaces due to undesirable development of biofilms causing a decrease and subsequent loss of productivity in water treatment settings. Continuous use of synthetic chemicals against biofouling is inept as it leads to the emergence of multi-antibiotic resistance. Application of natural products such as plants can be apt in curbing biofouling while checking the resistance challenge. This study aimed to evaluate the potential of Rosmarinus officinalis in the control of membrane biofouling. Bacteria from biofouling environments were subjected to a biofilm confirmation test and identified at cultural, morphological, biochemical and molecular levels. Leaves of R.officinalis were extracted in solvents of varying polarity and activities. These extracts were evaluated against bacterial biofilm formation via minimum biofilm inhibitory concentration (MBIC), minimum biofilm eradication concentration (MBEC) and mesocosm bioassays. Biofilm formation was confirmed in 68% of the isolates identified as Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus. The methanol and ethyl acetate extracts of R.officinalis indicated the least MICs (0.313mg/L and 1.25mg/L) against Pseudomonas aeruginosa and Staphylococcus aureus, respectively. Both extracts recorded the highest MBIC (50.00%) against Pseudomonas aeruginosa. The peak MBEC (57.88%) was obtained from the methanol extract against Staphylococcus aureus and this same extract inhibited 56.23% density of bacterial biofilms on glass slides.The methanol and ethyl acetate crude extracts of R. officinalis appreciably reduced bacterial biofilms; hence, this plant can be exploited as a natural antifouling agent, with reduced toxicity and low risk of resistance.