Biosynthesis of polyhydroxyalkanoates from sucrose by metabolically engineered Escherichia coli strains.

Sucrose utilization has been established in Escherichia coli strains by expression of Mannheimia succiniciproducens β-fructofuranosidase (SacC), which hydrolyzes sucrose into glucose and fructose. Recombinant E. coli strains that can utilize sucrose were examined for their abilities to produce poly(3-hydroxybutyrate) [P(3HB)] and poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] from sucrose. When recombinant E. coli strains expressing Ralstonia eutropha PhaCAB and SacC were cultured in MR medium containing 20 g/L of sucrose, all recombinant E. coli strains could produce P(3HB) from sucrose. Also, recombinant E. coli strains expressing Pseudomonas sp. MBEL 6-19 PhaC1437, Clostridium propionicum Pct540, R. eutropha PhaAB enzymes along with SacC could produce P(3HB-co-LA) from sucrose. Among the examined E. coli strains, recombinant E. coli XL1-Blue produced the highest contents of P(3HB) (53.60 ± 2.55 wt%) and P(3HB-co-LA) (29.44 ± 0.39 wt%). In the batch fermentations, recombinant E. coli XL1-Blue strains completely consumed 20 g/L of sucrose as the sole carbon source and supported the production of 3.76 g/L of P(3HB) and 1.82 g/L of P(3HB-co-LA) with 38.21 wt% P(3HB) and 20.88 wt% P(3HB-co-LA) contents, respectively. Recombinant E. coli strains developed in this study can be used to establish a cost-efficient biorefinery for the production of polyhydroxyalkanoates (PHAs) from sucrose, which is an abundant and inexpensive carbon source.