Even though most of the PHA synthases examined to date
are specific for the synthesis of either SCL- or MCL-PHAs,
at least six cases were recently reported to deviate from this
general finding. A PHA-negative mutant strain of
Pseudomonas putida harboring the PHA biosynthesis genes
of Thiocupsa pfennigii was able to accumulate a polyester
that consisted of 3-hydroxybutyrate, 3-hydroxyhexanoate
and 3-hydroxyoctanoate when cultivated on octanoate.
Also, a PHA-negative mutant strain of A. eutrophus harboring
these genes accumulated a terpolyester consisting of
3-hydroxybutyrate, 3-hydroxyhexanoate and 4-hydroxyhexanoate
when cultivated on 4-hydroxyhexanoate. 173
Rhodococcus ruber synthesized a copolyester of 3-hydroxybutyrate,
3-hydroxyvalerate, 3-hydroxyhexanoate and
4-hydroxyhexanoate from hexanoate. 173 Two strains of
Aeromonas sp. accumulated poly(3-hydroxybutyrate-co-3-
hydroxyhexanoate) when grown on fatty acids of more than
12 carbon atoms