PHAs structure and metabolism
PHAs are divided into two groups according to the number of
carbon atoms in the monomer units: short-chain length PHAs (scl-
PHAs) with 3e5 carbon atoms in each monomer unit, and mediumchain
length PHAs (mcl-PHA) with 6e14 carbon atoms in each unit
(Fig. 1). The most commonly produced monomer unit is poly-3-
hydroxybutyrate [P(3HB)]. Scl-PHAs with poly(3-
hydroxybutyrate-co-3-hydroxyvalerate copolymers [P(3HB-co-
3HV)] have mechanical properties that are considered more
desirable than P(3HB) homopolymers; mcl-PHAs are even more
desirable, because of their superior thermo mechanical properties.
The type of polymer produced is determined by the strain of bacteria
used.