Comparison of Anti-Biofilm Potential of Rhamnolipid Biosurfactant, Chemical Agents, and Coliphage Against E. coli Biofilm.

Biosurfactants are amphipathic microbial products that are released extracellularly or remain attached to the cell surface. The strong biofilm anti-adhesive and anti-biofilm properties of biosurfactants make them suitable candidates for application aimed at destroying troublesome bacterial biofilm. To investigate the anti-adhesion and biofilm disruptive properties of natural rhamnolipid biosurfactant, targeted isolation of a hydrocarbonoclastic bacteria from hydrocarbon-contaminated soil of Dakor, Gujarat, India, led to the isolation of bacteria producing biosurfactant, identified as Pseudomonas aeruginosa. DKR. The orcinol test preliminarily indicated that the biosurfactant was indeed rhamnolipid. The Fourier transform infrared spectroscopy and nuclear magnetic resonance further confirmed the biosurfactant as rhamnolipid. Pseudomonas aeruginosa DKR produced 25 mg/ml rhamnolipid that reduced the surface tension to 22.4 mN/m and possessed CMC (critical micellar concentration) of 130 mg/L. Sub-inhibitory dilution (0.25 mg/ml) of purified rhamnolipid DKR demonstrated superior antiadhesive and antibiofilm properties against biofilm-forming E. coli strains isolated from drinking water coolers in comparison to subinhibitory concentrations of common chemical surfactants, chelating agents, and weak acids used. Coliphage AM isolated on selected E. coli strains as hosts also demonstrated an appreciable biofilm anti-adhesive and anti-biofilm effect at 10⁶ Pfu/ml. This study emphasizes the utility of rhamnolipid biosurfactant DKR and Coliphage AM in lieu of chemicals as natural and eco-friendly agents in applications to eradicate biofilm from drinking water cooling containers, etc.