Production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) by metabolically engineered Escherichia coli strains

Recombinant Escherichia coli strains harboring a plasmid containing a novel artificial polyhydroxyalkanoate (PHA) operon consisting of the Aeromonas PHA biosynthesis related genes and Ralstonia eutropha reductase gene were developed for the production of poly(3-hydroxybutyrate-co-hydroxyhexanoate) [P(3HB-co-3HHx)] from dodecanoic acid. By applying stepwise reduction of dissolved oxygen concentration (DOC) during the fermentation, the final dry cell weight, PHA concentration, and PHA content of 79 g/L, 21.5 g/L, and 27.2 wt %, respectively, were obtained in 40.8 h, which resulted in the PHA productivity of 0.53 (g/L)/h. The 3HHx fraction slowly increased during the fed-batch culture to reach a final value of 10.8 mol %. The 3HHx fraction in the copolymer could be increased by 3-fold when the Aeromonas hydrophila orf1 gene was coexpressed with the PHA biosynthesis genes.