Single solvent polymer extraction methods

1. A method of isolating a PHA from a biomass containing the PHA, the method comprising:

contacting the biomass with a PHA extraction solvent to form a first combination comprising a PHA phase and a residual biomass phase;

separating the PHA phase from the residual biomass phase;

introducing the PHA phase into a PHA receiving solvent, thereby forming a second combination, wherein the PHA extraction solvent is capable of forming a minimum boiling azeotrope with the PHA receiving solvent;

maintaining the second combination at a temperature and pressure such that the PHA extraction solvent of the PHA phase and a portion of the PHA receiving solvent are removed from the second combination in the gaseous state as an azeotropic mixture; and

precipitating the PHA from the second combination when the PHA extraction solvent is substantially removed from the second combination;

wherein:

the PHA extraction solvent is selected from the group consisting of ketones, esters, alcohols and alkanes;

the PHA receiving solvent is water; and

the PHA extraction solvent has a higher boiling point than the PHA receiving solvent.

2. The method of claim 1 , wherein the minimum boiling azeotrope forms at a temperature below the boiling point of the PHA receiving solvent.

3. The method of claim 1 , wherein the precipitating comprises forming granules of the PHA.

4. The method of claim 3 , wherein the PHA granules have a bulk density of at least about 0.25 kg/m 3 .

5. A method of isolating a PHA, the method comprising:

combining the PHA, a PHA extraction solvent and a PHA receiving solvent to form a combination, the PHA extraction solvent being capable of forming a minimum boiling azeotrope with the PHA receiving solvent; and

maintaining the combination at a temperature and pressure such that the PHA extraction solvent is substantially removed and a portion of the PHA receiving solvent is removed from the combination in the gaseous state as a minimum boiling azeotropic mixture; and

precipitating the PHA from the combination as PHA granules;

wherein:

the PHA extraction solvent is selected from the group consisting of ketones, esters, alcohols and alkanes;

the PHA receiving solvent is water; and

the PHA extraction solvent has a higher boiling point than the PHA receiving solvent.

6. The method of claim 5 , wherein the PHA granules have a bulk density of at least about 0.25 kg/m 3 .

7. The method of claim 5 , wherein the minimum boiling azeotrope forms at a temperature below the boiling point of the PHA receiving solvent.

8. The method of claim 5 , wherein the precipitating the PHA comprises:

reducing the temperature of the combination after substantially removing the PHA extraction solvent and removing at least a part of the PHA receiving solvent as the minimum boiling azeotropic mixture.

9. The method of claim 8 , wherein the combining comprises:

combining the PHA and the PHA extraction solvent to form a first combination; and

combining the first combination with the PHA receiving solvent to form the combination.

10. The method of claim 1 , wherein the first combination is formed by agitating the biomass and the PHA extraction solvent.

11. The method of claim 1 , wherein the PHA extraction solvent is a single solvent and forms a binary azeotrope with a single PHA receiving solvent.

12. The method of claim 1 , wherein the PHA extraction solvent is MIBK, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone or butyl acetate.

13. The method of claim 12 , wherein the PHA extraction solvent is MIBK.

14. The method of claim 10 , wherein the agitating is effected by stirring.

15. The method of claim 5 , wherein the PHA extraction solvent is a single solvent and forms a binary azeotrope with a single PHA receiving solvent.

16. The method of claim 5 , wherein the PHA extraction solvent is MIBK, 2-pentanone, 3-pentanone, cyclopentanone, cyclohexanone or butyl acetate.

17. The method of claim 16 , wherein the PHA extraction solvent is MIBK.