– Bacterial synthesis is the most important process for PHA production at present.
– The synthesis of PHB is showed in Figure 5. The first step of the biochemical
pathway of PHB synthesis is the conversion of a selected carbon source to
acetate.
– The enzyme, called coenzyme A (CoA) is a universal carrier of acyl groups in
biosynthesis and acetyl-CoA is a basic metabolic metabolic molecule found in all
PHA-producing organisms.
– A dimer acetoacetyl-CoA is formed via reversible condensation and
subsequently reduced to a monomer unit (R)-3-hydroxybutyryl-CoA.
– PHB is formed via the polymerization of the (R)-3-hydroxybutyryl-CoA,
maintaining the asymmetric center.
– Propagation proceeds by bonding another monomer to the free thiol group of
the active site, followed by another thioester-oxyester exchange reaction to
form the trimer, and so on.