Role of β-oxidation and de novo fatty acid synthesis in the production of rhamnolipids and polyhydroxyalkanoates by Pseudomonas aeruginosa.

Pseudomonas aeruginosa are ubiquitous γ-proteobacteria capable of producing the biosurfactant rhamnolipids (RL) and the polymer polyhydroxyalkanoate (PHA). RL are glycolipids with high biotechnological potential, whereas PHA is used for the production of biodegradable plastics. It has been proposed that the β-oxidation pathway provides intermediates for RL biosynthesis, even when using a non-fatty acid carbon source for growth, while an intermediate of de novo fatty acid biosynthesis (FASII) pathway [(R)-3-hydroxyacyl-ACP] is used for PHA biosynthesis.

Overproduction of rhamnolipids in Pseudomonas aeruginosa PA14 by redirection of the carbon flux from polyhydroxyalkanoate synthesis and overexpression of the rhlAB-R operon.

Objective: To construct Pseudomonas aeruginosa PA14 derivatives that overproduce rhamnolipids (RL) by blocking the synthesis of the carbon-storage polymer polyhydroxyalkanoates (PHA) and by overexpressing the rhlAB-R operon that encodes for enzymes of RL synthesis and the RhlR transcriptional regulator.

Results: In contrast to previous results showing that overexpression of rhlAB-R genes in two P. aeruginosa strains (PAO1 and ATCC 9027) is sufficient to overproduce RL, we show that a PA14 derivative overexpressing the rhlAB-R operon did not increase the synthesis of these biosurfactants.