Production of Block Copolymer Poly(3-hydroxybutyrate)-block-poly(3-hydroxypropionate) with Adjustable Structure from an Inexpensive Carbon Source

The block copolymers poly(3-hydroxybutyrate)-block-poly(3-hydroxypropionate) (P3HB-b-P3HP) with a wide range of 3HP fractions from 7.4 mol % to 75 mol % were biosynthesized from inexpensive carbon sources for the first time, differing from previously reported approaches based on sequential addition of precursors. The engineered Escherichia coli strain carried two parallel synthetic pathways modulated by independent regulatory systems to produce the 3HB and 3HP monomers, respectively. Manipulating the expression levels of 3HB and 3HP pathways resulted in biosynthesis of block copolymers P3HB-b-P3HP with varied compositions. Nuclear magnetic resonance and differential scanning calorimetric studies demonstrated novel microstructure and thermal properties not available in related random copolymers and a blend of P3HB and P3HP homopolymers.