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

•Recombinant B. sacchari is able to produce copolymers with 20 mol% of 3HHx fraction.•A two-step bioprocess to control 3HHx fraction in the polyhydroxyalkanoate was proposed.•Aeromonas sp. PHA synthase has also specificity for 3HV and 3HHp monomers.•Modulated copolymers P(3HB-co-3HHx) are produced presenting different physical properties.

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 0.45 g l−1 h−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.

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