Polyhydroxyalkanoates (PHAs) are carbon and energy reserve material accumul
ated by numerous microorganisms and have been drawing much attention as bio
degradable substitutes for conventional nondegradable plastics and elastome
rs. There are a number of different PHAs having a variety of material prope
rties based on the different monomer composition. Poly(3-hydroxybutyrate) a
nd poly(3-hydroxybutyrate-co-3-hydroxyvalerate) are now efficiently produce
d by bacterial fermentation at reasonable production costs. Recent advances
in the production of short-chain-length (SCL) PHAs by bacterial fermentati
on are reviewed. Current status of the production of medium-chain-length (M
CL) PHAs and SCL-MCL-PHA copolymers is also reviewed.