Physicochemical Interactions between Rhamnolipids and Pseudomonas aeruginosa Biofilm Layers

This study investigated the physicochemical interactions between a rhamnolipid biosurfactant and a biofilm layer. A concentration of 300 mu g mL(-1) of rhamnolipids, which is around the critical micelle,concentration value (240 mu g mL(-1)), showedgreat potential for reducing biofilm, The surface free energy between the rhamnolipids and biofilm layer decreased, as did the negative surface charge, due to the removal of negatively charged humic-like, protein-like, and fulvic acid-like substances: The carbohydrate and protein cons centrations composed of extracellular polymeric sub-stances decreased by 31.6% and 79.6%, respectively, at a rhamnolipid concentration of 300 mu g mL(-1). In particular, thamnolipids can interact with proteins, leading to a reduction of the N source and amide groups on the membrane. For carbohydrates, the component ratio of glucosannne was decreased, but the, levels of glucose and mannose that form the majority of the carbohydrates remained unchanged. TO our knowledge, the present study is the first attempt at studying the interactions of the two phases of rhamnolipids and the biofilln layer, and as such IS expected to clarify the mechanism by which rhamnolipids lead to a reduction, in biofilm.