Efficient fermentation of di-rhamnolipids-rich products by P. aeruginosa using ethanol as solely carbon source

Abstract

High raw material costs critically limit rhamnolipids' industrial competitiveness against chemical synthetic surfactants. To address this, we developed a new fermentation process using low-cost ethanol (including industrial waste) as the sole carbon source by Pseudomonas aeruginosa PAO1. Through fed-batch optimization, a record rhamnolipid titer of 20.74 g/L was achieved—fivefold higher than batch fermentation. Further implementing sequential fed-batch fermentation over 21 days yielded an unprecedented cumulative production of 117.78 g/L, corresponding to 0.234 g/L/h average productivity (117 % improvement over optimized fed-batch fermentation). Crucially, ethanol-derived products contained 85.6 % di-rhamnolipids—significantly higher than conventional systems—while exhibiting performance parity with soybean oil-sourced counterparts. This work establishes a scalable, cost-efficient platform for high-value biosurfactant production, reducing dependency on expensive substrates while enabling industrial waste valorization.