Organisms are provided which express enzymes such as glycerol dehydratase, diol dehydratase, acyl-CoA transferase, acyl-CoA synthetase beta-ketothiolase, acetoacetyl-CoA reductase, PHA synthase, glycerol-3-phosphate dehydrogenase and glycerol-3-phosphatase, which are useful for the production of PHAs. In some cases one or more of these genes are native to the host organism and the remainder are provided from transgenes. These organisms produce poly(3-hydroxyalkanoate) homopolymers or co-polymers incorporating 3-hydroxypropionate or 3-hydroxyvalerate monomers wherein the 3-hydroxypropionate and 3-hydroxyvalreate units are derived from the enzyme catalysed conversion of diols. Suitable diols that can be used include 1,2-propanediol, 1,3 propanediol and glycerol. Biochemical pathways for obtaining the glycerol from normal cellular metabolites are also described. The PHA polymers are readily recovered and industrially useful as polymers or as starting materials for a range of chemical intermediates including 1,3-propanediol, 3-hydroxypropionaldehyde, acrylics, malonic acid, esters and amines.
