Extremely high-performance production of rhamnolipids by advanced sequential fed-batch fermentation with high cell density

Rhamnolipids are glycolipid biosurfactants that have extensive applications as cleaner alternatives to chemically synthesized surfactants. The cost of producing rhamnolipids is typically high due to the poor yields realized. This cost has limited their use in commercial applications. In this study, an advanced sequential fed-batch fermentation process with high cell densities was developed for the efficient fermentative production of rhamnolipids. With this approach, the total produced rhamnolipids reached over 665 g/L by Pseudomonas aeruginosa PAO1 during the fermentation period of 18 days, with an extremely high productivity of 1.54 g/L·h. This represents a more than a 5-time improvement over the regular fed-batch fermentation. The present advanced sequential fed-batch fermentation process is extremely efficient due to the high cell density and the presence of 18 g/L NaNO3 and 2 mg/L FeSO4·7H2O with enhanced mass-transfer efficiency, presenting a new strategy to improve the fermentation level of rhamnolipids.