enhanced rhamnolipids production by pseudomonas aeruginosa based on a ph stage-controlled fed-batch fermentation process

rhamnolipids find broad applications as natural surfactants, emulsifiers, and antibiotics because of their low toxicity, high biodegradability and environmental soundness. in this study, a ph stage-controlled process of fermentation of rhamnolipids by pseudomonas aeruginosa o-2-2 was established. a yield of 24.06 g/l in batch fermentation was achieved in a 5-l fermentor via the optimization of stirring speed. by controlling ph, rhamnolipid production was increased to 28.8 g/l, an improvement of 19.7%, and more substrate was converted to rhamnolipids rather than to biomass. fermentation kinetics models for cell growth, product synthesis and substrate consumption based on the ph stage-controlled fermentation indicated that rhamnolipid production could be further improved by fed-batch fermentation. rhamnolipid production reached 70.56 g/l, an improvement of 193%, in the ph stage-controlled fed-batch fermentation when the stirring speeds was controlled at 500 rpm and the fermentation temperature was maintained at 30 °c.