Production of poly(3-hydroxypropionate) and poly(3-hydroxybutyrate-co-3-hydroxypropionate) from glucose by engineering Escherichia coli

Poly(3-hydroxypropionate) (P3HP) is the strongest family member of microbial polyhydroxyalkanoates (PHA) synthesized by bacteria grown on 1,3-propandiol or glycerol. In this study synthesis pathways of P3HP and its copolymer P3HB3HP of 3-hydroxybutyrate (3HB) and 3-hydroxypropionate (3HP) were assembled respectively to allow their synthesis from glucose, a more abundant carbon source. Recombinant Escherichia coli was constructed harboring the P3HP synthetic pathway consisting of heterologous genes encoding glycerol-3-phosphate dehydrogenase (. gpd1), glycerol-3-P phosphatase (. gpp2) from Saccharomyces cerevisiae that catalyzes formation of glycerol from glucose, and genes coding glycerol dehydratase (. dhaB123) with its reactivating factors (. gdrAB) from Klebsiella pneumoniae that transfer glycerol to 3-hydroxypropionaldehyde, as well as gene encoding propionaldehyde dehydrogenase (. pdup) from Salmonella typhimurium which converts 3-hydroxypropionaldehyde to 3-hydroxypropionyl-CoA, together with the gene of PHA synthase (. phaC) from Ralstonia eutropha which polymerizes 3-hydroxypropionyl-CoA into P3HP. When phaA and phaB from Ralstonia eutropha respectively encoding β-ketothiolase and acetoacetate reductase, were introduced into the above P3HP producing recombinant E. coli, copolymers poly(3-hydroxybutyrate-. co-3-hydroxypropionate) (P3HB3HP) were synthesized from glucose as a sole carbon source. The above E. coli recombinants grown on glucose LB medium successfully produced 5. g/L cell dry weight containing 18% P3HP and 42% P(3HB-. co-84. mol% 3HP), respectively, in 48. h shake flask studies.