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

OBJECTIVES: 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.

RESULTS: 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-C10 -C10 and Rha-Rha-C10 -C10 detected by MALDI-TOF MS analysis with approx. 70% relative abundance, although a total of 21 rhamnolipid congeners were accumulated.

CONCLUSION: 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.