Production of medium-chain-length 3-hydroxyalkanoic acids by β-oxidation and phaC operon deleted Pseudomonas entomophila harboring thioesterase gene.

摘要

3-Hydroxyalkanoic acids (3HA) are precious precursors for synthesis of value added chemicals. According to their carbon chain lengths, 3HA can be divided into two groups: short-chain-length (SCL) 3HA consisting of 3-5 carbon atoms and medium-chain-length (MCL) 3HA containing 6-14 carbon atoms. To produce MCL 3HA, a metabolic engineered pathway expressing tesB gene, a thioesterase encoding gene that has been reported to catalyze acyl-CoA to free fatty acids, was constructed in Pseudomonas entomophila L48. When tesB of Escherichia coli encoding thioesterase II was introduced into polyhydroxyalkanoate (PHA) synthase and β-oxidation pathway deleted mutant of P. entomophila LAC31 derived from wild type P. entomophila L48, 6.65g/l 3-hydroxytetradecanoic acid (3HTD) and 4.6g/l 3-hydroxydodecanoic acid (3HDD) were obtained, respectively, when tetradecanoic acid or dodecanoic acid as related carbon sources was added in shake flask cultures. Moreover, 1.8g/l of 3-hydroxydecanoic (3HD) acid was also produced by P. entomophila LAC31 harboring PTE1 gene cloned from Saccharomyces cerevisiae using corresponding fatty acid decanoic acid. Interestingly, shake flask studies indicated that PTE1 harboring strain showed advantages over tesB expressing one for 3HDD and 3HD production, while tesB favored 3HTD production by P. entomophila LAC31. For the first time our study revealed that fine chemicals 3HTD, 3HDD or 3HD could be efficiently produced by metabolic engineered β-oxidation in Pseudomonas spp grown on related fatty acids.