Characterization of rhamnolipid biosurfactants produced by recombinant Pseudomonas aeruginosa strain DAB with removal of crude oil

To improve rhamnolipid production and its potential application in removal of crude oil, the recombinant Pseudomonas aeruginosa strain DAB was constructed to enhance yield of rhamnolipids. Strain DAB had a higher yield of 17.3 g rhamnolipids l(-1) in the removal process with crude oil as the sole carbon source than 10 g rhamnolipids l(-1) of wild-type strain DN1, where 1% crude oil was degraded more than 95% after 14 days cultivation. These rhamnolipids reduced the surface tension of water from 72.92 to 26.15 mN m(-1) with CMC of 90 mg l(-1). The predominant rhamnolipid congeners were Rha-C-10-C-10 and Rha-Rha-C-10-C-10 detected by MALDI-TOF MS analysis with approx. 70% relative abundance, although a total of 21 rhamnolipid congeners were accumulated. Increasing the copy number of rhlAB genes efficiently enhanced the production of rhamnolipids by the recombinant P. aeruginosa DAB and thus presents a promising application for the bioremediation process.