A non-naturally-occurring P(3HB-co-3HAMCL) is produced by recombinant Pseudomonas sp. from an unrelated carbon source.

Pseudomonas sp. PHA- was used as host for PHA biosynthesis genes from Aeromonas sp. to produce 3HB-co-3HAMCL from glucose with no supply of co-substrates. A non-naturally-occurring PHA composed mainly of 3HB, 3HHx and 3HD (3HO, 3HDdΔ5 and 3HDd monomers were detected in smaller amounts) was obtained. The polymer was extracted using two different solvents (acetone and chloroform) and subject to the following characterization tests: FTIR, DSC, TGA and GPC. The latter suggests a block copolymer since a single and narrow elution peak was observed for each sample. The DSC results ruled out the possibility of a random copolymer and agrees with a single copolymer composed of two blocks: one with the typical composition of PHAMCL produced by Pseudomonas and another containing 3HB and 3HHx with a high 3HHx molar fraction. Thus, this study increases the perspectives of P(3HB-co-3HAMCL) production from carbohydrates as the sole carbon source.

Combining molecular and bioprocess techniques to produce poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with controlled monomer composition by Burkholderia sacchari.

Biopolymers as polyhydroxyalkanoates (PHA) composed by different co-monomers 3-hydroxybutyrate and 3-hydroxyhexanoate [P(3HB-co-3HHx)] has attracted interest since its properties are similar to low density polyethylene. Burkholderia sacchari produces this copolymer with a very low 3HHx molar fraction, about 2 mol%. B. sacchari mutant (unable to produce polymer) was engineered to host PHA biosynthesis genes (phaPCJ) from Aeromonas sp. In addition, a two-step bioprocess to increase biopolymer production was developed. The combination of these techniques resulted in the production of P(3HB-co-3HHx) with 3HHx content up to 20 mol%. The PHA content was about 78% of dry biomass, resulting in PHA volumetric productivities around 0.45gl-1h-1. The P(3HB-co-3HHx) containing 20 mol% of 3HHx presented an elongation at brake of 945%, higher than reported before for this PHA composition. Here we have described an approach to increase 3HHx content into the copolymer, allowing the precise control of the 3HHx molar fractions.