Microbial production of rhamnolipid: Synthesis and potential application in bioremediation of hydrophobic pollutants

Biosurfactants are structurally diverse amphiphilic compounds containing both hydrophobic (nonpolar) and hydrophilic (polar) moieties synthesized by microorganisms. These microbial compounds exhibit a variety of useful properties as emulsifying, foaming, wetting, solubilizing, antiadhesive, and antimicrobial agents in diverse sectors such as environmental, food, pharmaceutical, and cosmetics. Among the biosurfactants, rhamnolipids are the most extensively studied both for detailed characterization and its application. Rhamnolipid belongs to glycolipid class and is comprised of one or two rhamnose molecules (hydrophilic part) bound to 3-hydroxy fatty acid chains (hydrophobic part). These molecules are less toxic and easily biodegradable in comparison to synthetic surfactants and are predominantly produced by Pseudomonas species. Genetically it is well delineated that rhamnosyltransferase genes are responsible for the synthesis of rhamnose molecule. Moreover, they are effectively utilized for increasing the solubility and degradation rate of hydrophobic organic pollutants like pesticides, polyaromatic hydrocarbons, and crude oil.