Poly-3-hydroxybutyrate chemical methods

Polymers derived from renewable resources (biopolymers) are broadly classified according to the method of production (1) Polymers directly extracted/ removed from natural materials (mainly plants) (e.g. polysaccharides such as starch and cellulose and proteins such as casein and wheat gluten), (2) polymers produced by "classical" chemical synthesis from renewable bio-derived monomers [e.g. poly(lactic acid), poly(glycolic acid) and their biopolyesters polymerized from lactic/glycolic acid monomers, which are produced by fermentation of carbohydrate feedstock] and (3) polymers produced by microorganisms or genetically transformed bacteria [e.g. the polyhydroxyalkanoates, mainly poly(hydroxybutyrates) and copolymers of hydroxybutyrate (HB) and hydroxyvalerate (HV)] [4]. 

Because PHAs are polymers composed of chiral building blocks, hydrolysis of PHAs leads to the release of the chiral monomers, which are valuable starting material for the synthesis of pharmaceuticals and specialty chemicals. An efficient method has been reported for the production of enantiomerically pure (R)-(-)-hydroxyalkanoic acids by in vivo depolymerization of PHAs (Lee et al. 1999c). Those (R)-(-)-3-hydroxyalkanoic acids of 4—12 carbon atoms and (R)-(-)-3-hydroxy-5-phenylvaleric acid were prepared by providing the environmental condition under which cells possess a high activity of intracellular PHA depolymerase and a low activity of a key enzyme that could convert the chiral monomer into another compound. Monomer (R)-(-)-3-hydroxybutyric acid could be produced at a high yield in 30 min by in vivo depolymerization of poly(3HB) accumulated in Alcaligenes latus. 

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