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

Abstract 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.