Abstract: A method of producing polyhydroxyalkanoate (PHA) copolymers comprising both short-chain-length (scl) and medium-chain-length (mcl) subunits, wherein some of the mcl subunits bear reactive vinyl groups, is provided. The method comprises providing cells comprising (i) a PHA synthase (phaC) gene encoding a particular class I poly(3-hydroxyalkanoate) polymerase, and (ii) a phaJ gene encoding a particular (R)-specific enoyl-CoA hydratase, and cultivating said cells in a growth medium comprising an alkenoic acid. In one example, cells grown in the presence of a mixture of decanoic acid and undecen-10-enoic acid yielded a copolymer comprising units of 3-hydroxybutyrate (94.73 mol %), 3-hydroxyhexanoate (1.51 mol %), 3-hydroxyoctanoate (2.33 mol %), 3-hydroxydecanoate (0.69 mol %) and 3-hydroxyhept-6-enoate (0.73 mol %). The presence of acrylic acid as a 13-oxidation inhibitor in the growth medium led to an increase in both the mcl-PHA subunit content and vinyl subunit content.

Abstract: A method is provided for producing medium chain length poly(3-hydroxyalkanoate) (MCL-PHA) with a selected ratio of monomers. A method of controlling the ratio of monomers in MCL-PHA is also provided which includes fermenting naturally occurring microorganisms with a fatty acid substrate, a food source and an additive. The methods provided do not sacrifice cell growth and maintenance and provide high yields of MCL-PHAs. MCL-PHAs are provided that are copolymers of Cn and Cn?2 monomers, where (n is 6-18).

Abstract: A method is provided for producing medium chain length poly(3-hydroxyalkanoate) (MCL-PHA) with a selected ratio of monomers. A method of controlling the ratio of monomers in MCL-PHA is also provided which includes fermenting naturally occurring microorganisms with a fatty acid substrate, a food source and an additive. The methods provided do not sacrifice cell growth and maintenance and provide high yields of MCL-PHAs. MCL-PHAs are provided that are copolymers of Cn and Cn-2 monomers, where (n is 6-18).

Abstract: Hypochlorite digestion of bacterial biomass to recover intracellular poly-.beta.-hydroxylalkanoic acid (PHA) has not been used on a large scale since it has been widely reported to severely degrade the polymer. The process of the invention proposes to optimize the initial biomass concentration, the digestion time and pH of the hypochlorite solution to minimize degradation. Consequently, PHA of up to 95% purity with an average molecular weight of 600,000 can be recovered from biomass initially containing PHA having a molecular weight of 1,200,000. By incorporating a pretreatment step with an anionic surfactant solution, PHA of 99% purity with a molecular weight of 1.20.times.10.sup.6 was obtained from biomass containing 57% PHA by weight with an initial molecular weight of 1.25.times.10.sup.6.