continuous cultivations have been carried out to improve
productivity.
Among the various members of PHAs, only
three kinds of PHAs, P(3HB), poly(3-hydroxybutyrate-co-
3-hydroxyvalerate) [P(3HB-co-3HV)If and poly(3-
hydroxyhexanoate-co-3-hydroxyoctanoate) [P(3HHx-co-
3H0)], have been produced to a relatively high concentration
with high productivity. This seems to be either due to
the difficulty of developing cultivation strategy using unusual
(and expensive) carbon substrates or due to the lack of
applications that justify the high production cost. However,
when the needs are met, these unusual polyesters may be
produced with high productivity using the strategies similar
to those described below.