Engineering Pseudomonas entomophila for synthesis of copolymers with defined fractions of 3-hydroxybutyrate and medium-chain-length 3-hydroxyalkanoates

Abstract Polyhydroxyalkanoates(PHA) composed of both short-chain-length (SCL) and medium-chain-length (MCL) monomers (SCL- co -MCL PHA) combine the advantages of high strength and elasticity provided by SCL PHA and MCL PHA, respectively. Synthesis of SCL- co -MCL PHA, namely, copolymers of 3-hydroxybutyrate (3HB) and MCL 3-hydroxyalkanoates (3HA) such as 3-hydroxydecanoate (3HD) and longer chain 3HA, has been a challenge for a long time. This study aims to engineer Pseudomonas entomophilafor synthesizing P(3HB- co -MCL 3HA) via weakening its β -oxidation pathway combined with insertion of 3HB synthesis pathway consisting of β -ketothiolase ( phaA ) and acetoacetyl-CoA reductase( phaB ). 3HB and MCL 3HA polymerization is catalyzed by a low specificity PHA synthase ( phaC ), namely, mutated PhaC61-3. The link between the fatty acid de novo synthesisand PHA synthesis was further blocked to increase the supply for SCL and MCL monomers in P. entomophila . The so-constructed P. entomophila was successfully used to synthesize novel PHA copolymers of P(3HB- co -3HD), P(3HB- co -3HDD) and P(3HB- co -3H9D) consisting of 3HB and 3-hydroxydecanoate (3HD), 3-hydroxydodecanoate (3HDD) and 3-hydroxy-9- decanent(3H9D), respectively. MCL 3HA compositions of P(3HB- co -3HD) and P(3HB- co -3HDD) can be adjusted from 0 to approximate 100 mol%. Results demonstrated that the engineered P. entomophila could be a platform for tailor-made P(3HB- co -MCL 3HA).