Rhamnolipids

Rhamnolipids are glycolipid biosurfactants produced primarily by Pseudomonas aeruginosa. They consist of one or two rhamnose sugar units linked to hydroxy fatty acid chains, typically with two C10–C12 tails. Mono-rhamnolipids and di-rhamnolipids are the main congeners; their amphiphilic structure enables surface activity and the formation of micelles and emulsions.

Biosynthesis involves the rhlAB operon, with rhlC adding a second rhamnose to form di-rhamnolipids. Production is regulated by quorum sensing systems (Las and Rhl) and is influenced by nutrient conditions. While P. aeruginosa is the primary source, rhamnolipids can be produced by other microbes or engineered strains.

Functionally, rhamnolipids reduce surface tension and facilitate wetting of hydrophobic substrates. They emulsify oils, aid in biofilm dynamics, and can disrupt cellular membranes at higher concentrations.

Applications include environmental bioremediation of hydrocarbon-contaminated soils and waters, and use as green emulsifiers in detergents, cosmetics, and potentially drug formulations. Production and use face biosafety and regulatory considerations due to association with a pathogenic organism, prompting interest in non-pathogenic producers and sustainable substrates.