DD276304A1 - METHOD FOR CLEANING MICROBIOLOGICALLY PRODUCED POLYMERIC BETA HYDROXYCARBONE ACIDS - Google Patents

Abstract

The invention relates to a process for obtaining dye-free and solvent-free polymeric b-hydroxycarboxylic acids which have been obtained by extraction from bacterial biomass. According to the invention, the object is achieved by extractively treating the extracted, precipitated and dried polyester in the temperature range from 0C to 100C with a water-soluble organic solvent in which the polyester is insoluble, but which has a high solubility for the dye. The inventive method has the advantage of bringing about a much more effective removal of dye and extractant residues from the polymer in one step, as is the case in Umfallellungsprozessen.

Description

Field of application of the invention

The invention relates to a process for obtaining dye-free and solvent-free polymeric β-hydroxycarboxylic acids which have been obtained by extraction from bacterial biomass.

Characteristic of the known technical solutions Various strains of bacteria form polymeric β-hydroxybutyric acid, among others, under certain fermentation conditions. Polyhydroxycarboxylic acids, such as. B. ß-hydroxyvaleric acid as storage substances. In addition, among these Conditions dyestuffs and lipids formed, which according to EP 15123, EP 58480 and EP 124309 expediently before the PHB extraction can be largely removed by extraction of the biomass with lower alcohols or acetone. To recover the polyesters, various extraction methods are known which chlorinated as specific solvents Hydrocarbons such as chloroform (US-PS 327561O), 1,2-dichloroethane (EP 14490 and EP 15123) and mixtures of

1,2-cichloroethane with methanol or ethanol (DD-WP 239609) or of methylene chloride with ethanol (US-PS 3044942) use.

All these methods have in common that the extracted poly-ß-hydroxybuttersäuro (PHB) from the solution by means of Precipitating agents or when using the solvent mixtures is precipitated by lowering the temperature. When Precipitants are generally methanol, ethanol or acetone. The precipitated PHB is used to remove a solvent Drying under normal pressure and / or subjected to vacuum. For the removal of dye residues left in the extracted and precipitated PHB, usually a

repeated reprecipitation of PHB carried out using the solvents and precipitants mentioned.

All processes listed have the disadvantage that both larger amounts of chlorinated hydrocarbons and Fällungsmittelbestandteile remain as well as dye residues in the final product, as these by a hot water wash of from

or umgefillten end product as proposed in DD-WP 229428 and in US Patent 4101533, can not be removed.

Object of the invention

The aim of the invention is to obtain a product free from organic solvents and dyes of polymeric β-hydroxy carboxylic acids with reduced expenditure.

Essence of the invention The invention is based on the object, the extracted and precipitated polyester such a treatment

undergo a dye and solvent free dry product can be made.

Erfindungsyemäß the object is achieved in that the extracted, precipitated and dried polyester in the Temperature range of OT to 100 ⁰ C is treated extractively with a water-soluble organic solvent, in the

the polyester is insoluble but which has high solubility for the dye.

It was found that the dye in the drying process of the precipitated polyester to the surface of the agglomerates

and can be removed by a simple wash-off process with the water-soluble organic solvent, whereas reprecipitation due to the unfavorable solubility conditions less protection of the

Dye from the polymer causes. Surprisingly, it was found that at the same time a nearly complete Protection of the residual precipitants remaining in the polymer is carried out. Contrary to all expectations, it was found that the solvents used to wash off the dye are not in the Polymer scaffolding able to penetrate. After this solvent treatment of the polyester, water extraction by the known method is no longer

required because a dye- and solvent-free dry product of polymeric ß-hydroxycarboxylic acid is obtained.

Particularly suitable solvents for the proposed process are methanol, ethanol and acetone, individually or in the form of Mixture. The inventive method has the advantage, in one step, a much more effective removal of

Dye and extractant residues from the polymer bring about, as is the case with Umfallungsprozessen. Depolymerizations of the polyester, as occur according to the confessional method using ethylene or propylene carbonate (US Pat. No. 4,101,533) or acetic anhydride (DC-WP 229428), are effectively prevented because molecular weight degradation of the polymer in the proposed temperature range and in the solvents proposed not taking place. In the following examples, the invention is explained in more detail:

example 1

From a fermented on a methanol-containing substrate culture of Methylobacter spec, a bacterial dry mass was prepared by spray drying, containing 55Ma .-% PHB. By extraction with chloroform for 30 minutes in a mass ratio of solvent: solid of 5: 1 at the boiling point of the extractant, precipitation of the miscella with acetone in the volume ratio of 1: 1 and drying in vacuo, pink PHB with a molecular weight of MW = 105,000 at a degree of extraction of 97 % receive. The chloroform content of this PHB was 1.6 mass%. Treatment with ethanol in a weight ratio solvent: 2.5: 1 at a temperature of 50 ° C. for 30 minutes and subsequent drying in vacuo gave a completely decolorized product, at the same time achieving a chloroform enrichment of the PHB to 0.4% by mass , The same treatment at a temperature of 70 ⁰ C reduced the Chlorolormgehalt of the polymer to a value of 0.012 wt .-%. Other solvents (ethanol, acetone) were not detectable by chromatography in the solid.

Example 2

The fermented and extracted as in Example 1 PHB was treated with methanol in a weight ratio LösungsmittehFeststoff of 2: 1 at 3O ⁰ C and at 60 ⁰ C for 30 minutes. The vacuum-dried product was free of dye and had a chloroform content of 0.45 Ma.% And 0.014 Ma.%, Respectively. Other solvents were not detectable by gas chromatography.

Example 3

The PHB fermented and extracted as in Example 1 was treated with acetone in a weight ratio acetone solids of 2.5: 1 at a temperature of 50X30 and 60 minutes. The resulting dye-free products had chloroform contents of 0.027 wt .-% bz. 0.015% by mass. Other solvents were undetectable by gas chromatography.

Example 4

The fermented as in Example 1 biomass was extracted for 30 minutes under reflux with 1,2-dichloroethane in a weight ratio of 1: 5. The resulting miscella was precipitated with acetone in the volume ratio of 1: 1. The refined PHB was separated and dried in vacuo. The product obtained was pink and had a molecular weight of MW = 107,500, a content of 1,2-dichloroethane of 1.75 Ma .-%. Treatment with a 1: 1 mixture of methanol and ethanol in a weight ratio LösungsmittehFeststoff of 3: 1 for 30 minutes at a temperature of 60 ⁰ C and subsequent drying in vacuo resulted in oinem completely discolored product with a content of 1,2-dichloroethane of 0.01% by mass. Other solvents were not detectable by gas chromatography in the solid.

Claims (3)

1. A process for the purification of microbiologically produced poly-.beta.-hydroxycarboxylic acids, in particular for the removal of solvent and / or dye residues, by solvent extraction, characterized in that, extraction of the precipitated poly-.beta.-hydroxycarboxylic acids with water-soluble organic solvents, in which the poly β-hydroxycarboxylic acid is insoluble, but the impurities to be removed are soluble, within a temperature range of 0 to 100 ⁰ C. 2. The method according to claim 1, characterized in that a solvent / solids ratio of 1: 1 to 20: 1, preferably 2: 1 to 5: 1, is applied. 3. The method according to claim 1 and 2, characterized in that are used as a solvent methanol, ethanol, acetone alone or in admixture.