Prospects for using native and recombinant rhamnolipid producers for microbially enhanced oil recovery

Abstract

EOR effects of cell-containing supernatants from cultures of native rhamnolipid producer Pseudomonas aeruginosa PA14, recombinant Escherichia coli carrying genes responsible for rhamnolipid production and P. aeruginosa PDO111 with repressed transcription of rhamnolipid production genes were studied and compared to EOR effects of chemical surfactants in experiments with sandpack columns. The P. aeruginosa PA14 rhlAB genes responsible for production of mono-rhamnolipids were PCR amplified and inserted into pNOT19 plasmid to produce a vector pF1bR4 that was used for transformation of E. coli TG2 to get recombinant strain E. coli pF1bR4. P. aeruginosa PA14, E. coli pF1bR4, and P. aeruginosa PDO111 were grown for 24h at 37°C and centrifuged at 3000rpm for 12min. MALDI-TOF analysis allowed finding previously described rhamnolipids in P. aeruginosa PA14 culture supernatant extract, but not in E. coli pF1bR4 or P. aeruginosa PDO111 extracts. Flooding and incubation tests with sandpack model columns containing two types of oil showed that culture supernatants did have EOR potential. Presence of rhamnolipids and some other biosurfactants including cell surface parts and/or bacterial cells led to enhancement of oil recovery when two different oil production mechanisms, water-flood drive and solution-gas drive, were applied.