Extraction Separation of Rhamnolipids by n‐Hexane via Forming Reverse Micelles

Abstract

AbstractRhamnolipids (RL) have been regarded to be insoluble in n‐hexane. Unexpectedly, we have noticed that RL could be extracted together with vegetable oil by n‐hexane at analyzing oil content of fermentation broth. This paradoxic phenomenon was assumed to be due to the formation of reverse micelles. As found in this paper, the micelle size as well as conductivity increased due to water solubilization, illustrating the formation of reverse micelles of RL in n‐hexane. In this reverse micellar system, the maximal water solubility was detected to be 6.26 mol H2O/mol RL while the reverse critical micelle concentration of RL was around 3% (w/w). Hence, it seems that the presence of water could increase the dissolution of RL in n‐hexane via forming the reverse micelles of RL/n‐hexane/water. Lastly, the formation of reverse micelles was further applied for extraction of RL by n‐hexane. Using this method, over 99.0% of RL was extracted under the appropriate pH of 4.5. This extraction separation using n‐hexane instead of chloroform proposed a much cleaner and safer strategy in RL manufacture. Moreover, the capability of RL in forming reverse micelle system could benefit the future application on improving enzymatic reactions, stabilizing nanoparticles, environmental treatment, and protein folding, etc.