Production of beta-hydroxybutyrate polymers

Claim 2

A process for the production of a β-hydroxybutyrate polymer having at least 40 mole % of β-hydroxybutyrate units in the polymer chain comprising cultivating a micro-organism that is capable of accumulating said polymer in an aqueous medium on an assimilable carbon source, at least part of the cultivation being conducted under conditions that cause said micro-organism to accumulate said polymer within the micro-organism cells, and then separating said polymer accumulated in said micro-organism cells from the other cell material, characterised in that the carbon of at least part of said assimilable carbon source comprises carbon from cell material separated from the β-hydroxybutyrate polymer of β-hydroxybutyrate polymer-containing cells of said micro-organism.

Claim 3

A process according to claim 1 characterised in that said at least part of the assimilable carbon source comprises solubilised cell material separated from the β-hydroxybutyrate polymer of β-hydroxybutyrate polymer-containing cells of said micro-organism.

Claim 4

A process according to claim 2 characterised by solubilising at least part of the cell material, other than said β-hydroxybutyrate polymer, of said micro-organism cells produced in the cultivation step, and recycling said solubilised cell material to the cultivation step as part of the assimilable carbon source used therein.

Claim 5

A process according to claim 2 or claim 3 characterised in that said solubilisation comprises treatment of the cell material with an enzyme composition.

Claim 6

A process according to claim 4 characterised in that said solubilisation comprises digesting said &-hydroxybutyrate polymer-containing cells with a proteolytic enzyme composition and thereafter separating the solubilised cell material from the β-hydroxybutyrate polymer-containing residue.

Claim 7

A process according to any one of claims 2 to 5 wherein said solubilisation comprises heating said cell material in an aqueous medium at 50 to 150 C.

Claim 8

A process according to any one of claims 1 to 6 wherein the cultivation of the micro-organism is conducted continuously.

Claim 9

A process according to claim 7 wherein the micro-organism is first cultivated in an aqueous medium on an assimilable carbon source in a first vessel and then the aqueous medium containing the micro-organism cells is continuously or intermittently transferred to a second vessel wherein cultivation of said micro-organism on an assimilable carbon source is continued in the presence of such a restricted amount of a nutrient required for growth, but not polymer accumulation, that said polymer is accumulated by said micro-organism during the cultivation in said second vessel, characterised in that only the carbon of the assimilable carbon source employed for the cultivation in said first vessel comprises the carbon derived from the cell material separated from the β-hydroxybutyrate polymer of β-hydroxybutyrate polymer-containing cells of said micro-organism.