Chemistry: molecular biology and microbiology – Micro-organism – tissue cell culture or enzyme using process... – Preparing oxygen-containing organic compound
Patent
1997-06-16
1999-04-13
Lilling, Herbert J.
Chemistry: molecular biology and microbiology
Micro-organism, tissue cell culture or enzyme using process...
Preparing oxygen-containing organic compound
435136, 435146, 435259, 435267, 435829, 435874, 528354, 528358, 528361, 560185, C12P 762, C12P 742
Patent
active
058940626
DESCRIPTION:
BRIEF SUMMARY
THIS INVENTION relates to a process for the recovery of polyhydroxyalkanoic acid.
It has been found that it is possible to produce polyhydroxyalkanoic acid for example polyhydroxybutyric acid in microorganisms, for example Alcaligenes and in plants. The recovery of the polymer, especially from plants in a state of sufficient purity for it to be useable as a plastics material presents difficulties however. Matter derived from plants for example seeds and fruits is herein referred to as vegetable matter.
Surprisingly we have found that it is possible to carry out an effective separation of polyhydroxy-alkanoic acid from matter derived from organisms which contains it by dissolving the polyhydroxyalkanoic acid (PHA) in a solvent which is a lower ketone, dialkyl ether or a lower alcohol or an ester thereof, separating the solution so formed from undissolved matter and recovering PHA from the solution.
The invention therefore comprises a process in which a polymer of a hydroxyalkanoic acid (PHA)is recovered from matter derived from living organisms which comprises dissolving the PHA in a solvent which is a lower ketone, dialkyl ether, a lower alcohol or an ester thereof, separating the solution from such matter and recovering PHA from the solution.
The process is very suitable for the recovery of polymers and copolymers of hydroxybutyric acid for example a polymer of hydroxybutyric and hydroxyvaleric acids.
It is often desirable to crush or mill the vegetable matter prior to contacting it with the solvent in order to permit more intimate contact of the solution with the PHA.
If the solvent is miscible with water it is preferred that the PHA be precipitated from the solution by adding water. Solvents which are immiscible with water may also be used in which case the PHA may be recovered by evaporating the solvent or by temperature cycling by which the PHA is dissolved at a high temperature and the solution cooled to precipitate PHA. The solvent may in the latter case be reused for further extraction of PHA but it is desirable if this is done to replace at least part of the solvent by fresh solvent so as to prevent undue build up of impurities on continued recycle of the solvent. Fresh solvent may be produced by distilling pure solvent from used impure solvent.
Preferred water miscible solvents include lower ketones, especially acetone and lower alcohols for example methanol, ethanol, or a propanol which is suitably isopropanol. Such solvents may be used in the presence or absence of water. For example ethanol/water mixtures may be used which can be but are not limited to azeotropic compositions.
If the vegetable matter contains oil it is preferred that the oil be extracted from the vegetable matter before it is treated according to this invention. This may be done by pressing the vegetable matter to expel oil and/or by extracting it with a water immiscible solvent which is suitably a paraffin or cyclo-paraffin containing for example 4 to and preferably 5 to 8 carbon atoms. The water immiscible solvent is preferably one which does not dissolve substantial quantities of PHA.
If desired oil and PHA may be extracted together from vegetable matter by dissolving them in a solvent, separating the solids from undissolved vegetable matter and separating the PHA from the solution, for example by cooling to precipitate it or adding a liquid which reduces its solubility in the solvent, for example water.
The solvent extraction is preferably carried out at a temperature above 100.degree. C. and preferably above 120.degree. C. It is however preferred that the temperature should not substantially exceed 150.degree. C. in order to avoid depolymerisation of the PHA. Suitably a ratio of 1.5:1 to 10:1 of solvent (ml) to solid (grams) should be used so as to secure easy handling of the mixture of vegetable matter and solvent and effective recovery of PHA. PHA may be recovered by cooling the solution for example to 20-80.degree. C. and preferably 30 to 50.degree., or by evaporating the solvent. If a water miscible solvent is employe
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Bond Gary M.
Lilling Herbert J.
Monsanto Company
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