Engineering the biosynthesis of novel rhamnolipids in Escherichia coli for enhanced oil recovery

Aims: The interfacial tension of rhamnolipids and their applications in enhanced oil recovery are dependent on their chemical structures and compositions. To improve their performances of interfacial tension and enhanced oil recovery, the engineered strategies were applied to produce novel rhamnolipids with different chemical structures and compositions. Methods and Results: By introducing different key genes for rhamnolipid biosynthesis, Escherichia coli was firstly constructed to produce rhamnolipids that showed different performances in interfacial tension from those from Pseudomonas aeruginosa due to the different fatty acyl compositions. Then, the mutant RhlBs were created by directed evolution and subsequent site-directed mutagenesis and resulted in the production of the novel rhamnolipids with the different performances in interfacial tension as well as enhanced oil recovery. Lastly, computational modelling elucidates that the single amino acid mutation at the position 168 in RhlB would change the volume of binding pocket for substrate and thus affect the selectivity of rhamnolipid formation in E. coli. Conclusions: The novel rhamnolipids that showed the improved performances of interfacial tension and the potential different applications in enhanced oil recovery were successfully produced by engineered E. coli. Significance and Impact of the study: This study proved that the combination of metabolic engineering and protein engineering is an important engineered strategy to produce many novel metabolites in micro-organisms.