Comparative study of the production of rhamnolipid biosurfactants by B. thailandensis E264 and P. aeruginosa ATCC 9027 using foam fractionation

Biosurfactants are surface-active agents that are produced by a variety of microorganisms including yeasts, filamentous fungi and bacteria. In this work, we report on the ability of Pseudomonas aeruginosa ATCC 9027 and Burkholderia thailandensis E264 to produce rhamnolipids via a 10-L bioreactor and their recovery through foam fractionation studies in a continuous stripping mode. The recovery of Rha-C 10 -C 10 (mono-rhamnolipids) produced by P. aeruginosa ATCC 9027 increased (from 6% to 96%), whilst the enrichment decreased (from 2.9 to 1.2) with the increasing airflow rate. These results are consistent with foam fractionation of a single surfactant system with stable foam. The recovery and enrichment of Rha-Rha-C 14 -C 14 (di-rhamnolipids) produced by B. thailandensis E264 (and an unknown molecule) in a single-component system were found to display different characteristics. Both recovery and enrichment were found to decrease with the airflow rate. It is postulated that a competitive adsorption process could occur between the smaller molecule identified by electrospray ionisation–mass spectrometry (ESI–MS) and Rha-Rha-C 14 -C 14 .