Methods are provided for separating polyhydroxyalkanoates ("PHAs") from plants, such as transgenic oil crop plants. The methods advantageously permit both the oil and the PHAs to be recovered from the plant biomass. To isolate the PHAs, in one embodiment, a biomass derived from an oil crop plant is pre-processed, for example by grinding, crushing or rolling. The oil then is extracted from the biomass with a first solvent in which the oil is soluble and in which the PHAs are not highly soluble to remove the oil. The biomass then can be extracted with a second solvent in which the PHA is soluble, to separate the PHA from the biomass. Alternatively, the PHA-containing biomass is treated with a chemical or biochemical agent, such as an enzyme, to chemically transform the PHA into a PHA derivative. The PHA derivative then is separated from the mixture using, for example, a physical separation process such as distillation, extraction or chromatography. Advantageously, using the method, the plant oils, the PHAs and PHA derivatives can be recovered and purified on a large scale from oil containing plants such as transgenic oil crop plants.

Methods are provided for separating polyhydroxyalkanoates ("PHAs") from plants, such as transgenic oil crop plants. The methods advantageously permit both the oil and the PHAs to be recovered from the plant biomass. To isolate the PHAs, in one embodiment, a biomass derived from an oil crop plant is pre-processed, for example by grinding, crushing or rolling. The oil then is extracted from the biomass with a first solvent in which the oil is soluble and in which the PHAs are not highly soluble to remove the oil. The biomass then can be extracted with a second solvent in which the PHA is soluble, to separate the PHA from the biomass. Alternatively, the PHA-containing biomass is treated with a chemical or biochemical agent, such as an enzyme, to chemically transform the PHA into a PHA derivative. The PHA derivative then is separated from the mixture using, for example, a physical separation process such as distillation, extraction or chromatography. Advantageously, using the method, the plant oils, the PHAs and PHA derivatives can be recovered and purified on a large scale from oil containing plants such as transgenic oil crop plants.

Polyhydroxyalkanoate (PHA) polyester is extracted from biomass by dissolving the PHA in a non-halogenated solvent which comprises a PHA-good solvent or a mixture thereof. Suitable PHA-good solvents can be selected from the disclosed alcohols, esters, amides and ketones. The PHA can be recovered, for example, by cooling, by solvent evaporation, or by addition of a PHA-poor solvent, wherein the PHA-poor solvent preferably dissolves less than about 1% (w/v) of the PHA at a temperature below the solvent boiling point. Preferred PHA types for use in the invention are poly (hydroxybutyrate-co-hydroxyvalerate), poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and polymers/copolymers of hydroxyterminated polyhydroxybutyrate.

Polymer extraction methods are disclosed.

The invention relates to processes for extracting polyhydroxyalkanoate from a biomass, comprising admixing the biomass with an organic solvent for from 1 second to 15 minutes at a first temperature of from 5.degree. C. below the melting point of the polyhydroxyalkanoate to 10.degree. C. above the melting point of the polyhydroxyalkanoate and at a pressure of from 1 bar to 10 bar to provide a composition comprising the organic solvent and polyhydroxyalkanoate.