Role of β-oxidation and de novo fatty acid synthesis in the production of rhamnolipids and polyhydroxyalkanoates by Pseudomonas aeruginosa
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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. The aim of this work is to study the inter-relationship of the RL and PHA biosynthetic pathways in a culture medium with a non-fatty acid carbon source, focusing on the role of FASII and β-oxidation in supplying the substrates for the first step in RL and PHA synthesis, carried out by the RhlA and PhaG enzymes, respectively. The PHA synthases (PhaC1 and PhaC2) are only able to use CoA-linked 3-hydroxy acids and the PhaG enzyme catalyzes the conversion of (R)-3-hydroxyacyl-ACP to (R)-3-hydroxyacyl-CoA, the substrate of PhaC1 and PhaC2. RhlA in turn catalyzes the synthesis of the RL precursor 3-(3-hydroxyalkanoyloxy) alkanoic acids (HAA) by the dimerization of two 3-hydroxyalkanoic acid molecules (that have been shown to be also (R)-3-hydroxyacyl-ACP). In this work, we show that RhlA can produce both RL and PHA precursors (presumably CoA-linked HAA), that the blockage of carbon flux through β-oxidation pathway does not decrease RL titer, and that the enoyl-CoA hydratase RhlY and enoyl-CoA hydratase/isomerase RhlZ produce the main fatty acids precursor of RL using as substrate also a FASII intermediate (presumably (S)-3-hydroxyacyl-CoA).
KeywordsRhamnolipids Polyhydroxyalkanoates Fatty acid de novo biosynthesis β-Oxidation Pseudomonas aeruginosa
UGG is a doctoral student of Programa de Maestría y Doctorado en Ciencias Bioquímicas, Universidad Nacional Autónoma de México (UNAM), and this article was performed in partial fulfillment of the requirements for UGG doctorate degree. UGG (CVU-422007) received a fellowship from CONACYT. This work was supported in part by grant IN201819 from Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica, (Dirección General de Asuntos del Personal Académico-UNAM) and grant 252269 from Consejo Nacional de Ciencia y Tecnología (CONACYT).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This work was performed following the “Código Ético para el Personal Académico del Instituto de Investigaciones Biomédicas, UNAM” (Ethical Manual of the Biomedical Research Institute, UNAM).
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