2.2.2 Copolymer PHA
In most cases, bacteria produce PHB. Also in many cases, short-chain-length
(scl) PHA copolymers are synthesized consisting of C3 and C5, including poly[(R)-
3-hydroxypropionate-co-(R)-3-hydroxybutyrate] (Shimamura et al. 1994),
poly[(R)-3-hydroxybutyrate-co-4-hydroxybutyrate] (Saito et al. 1996), poly[(R)-3-
hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) (Alderete et al. 1993), and
poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate-co-4-hydroxybutyrate]
(Zhao and Chen 2007). Many Pseudomonas spp. are able to accumulate mcl PHA
copolymers containing C6–C12 monomers. Typical mcl PHA are poly[(R)-3-hydroxyhexanoate-
co-(R)-3-hydroxyoctanoate-co-(R)-3-hydroxydecanoate] and
poly[(R)-3-hydroxyhexanoate-co-(R)-3-hydroxyl-octanoate-co-(R)-3-hydroxydecanoate-(
R)-3-hydroxydodecanoate](Lageveen et al. 1988). Recently, the author’s
laboratory succeeded in producing poly[(R)-3-hydroxydecanoate-(R)-3-hydroxydodecanoate)]
(unpublished results).
Copolymers of scl and mcl PHA possess useful and flexible mechanical properties;
they are the preferred materials for application development. A successful
example is the PHBHHx that was produced on an industrial scale (Chen 2009b).
US-based Procter & Gamble has trademarked scl and mcl PHA copolymers of C4
and C6–C12 as NodaxTM (Noda et al. 2009).