2. Overview of PHA production
2.1. PHA production in pure cultures
The French bacteriologist Lemoigne first isolated
and characterized poly-3-hydroxybutyrate (P(3HB)) from
bacteria between 1923 and 1927 [27–33], and showed
that this extract could be cast into a transparent film.
Although it was some time before this discovery was
turned into a practical outcome, PHA production using
pure cultures still has a long history. Stanier and Wilkinson
and their co-workers were responsible for some of
the initial fundamental research into the mechanisms of
PHA biosynthesis, beginning in 1957 [34,35]. This was followed
in 1959 by the first attempted commercialization,
when W.R. Grace and Company patented a P(3HB) production
process using bacteria [36], although production
inefficiencies, poor thermal stabilities and a lack of available
extraction technologies limited this application. In
1970, Imperial Chemical Industries Ltd. commercialized
the production of P(3HB-co-3HV) under the trade name of
BiopolTM [37], with the technology since being sold to Monsanto
and then to Metabolix. Since that time, there have
been a range of new technologies developed, and recent
focus within pure culture production has been on the synthesis
of alternative copolymers such as P(3HB-co-3HHx)
(commercialized as NodaxTM) [38], a wide range of functionalized
PHAs (incorporating monomer units with novel
and active functionalities on the side chains) and also on
the use of metabolic engineering to reengineer the central
metabolism of PHA producers for more efficient PHA
production. In its simplest form, PHA production using
pure cultures adopts a two-stage batch production process