Abstract: A method of isolation of polyhydroxyalkanoates from biomass pre-cleans the biomass in a first extraction process by extracting components of the biomass other than polyhydroxyalkanoates. In a second extraction process, polyhydroxyalkanoates are extracted from a solid phase of the biomass obtained in the first extraction process by adding an extraction agent to pre-cleaned biomass based on chlorinated hydrocarbon, carrying out the extraction for 5 to 90 minutes at a temperature in the range of 20 to 120° C., separating the extract containing the polyhydroxyalkanoates from the extraction solution, and feeding the extract to a circulation loop filled with water having a temperature from 20 to 120° C. or a mixture of water and from up to 20% by weight of the extraction agent based on chlorinated hydrocarbon used for the extraction of polyhydroxyalkanoates, wherein the extraction agent is removed from this extract and polyhydroxyalkanoates precipitate.

Abstract: The invention relates to a method of isolation of polyhydroxyalkanoates from biomass fermented by microorganisms producing polyhydroxyalkanoates and/or from biomass containing at least one crop-plant producing polyhydroxyalkanoates in which from the biomass which, if fermented, is first inspissated by the isolation from a fermentation medium to a dry matter content of at least 20%, polyhydroxyalkanoates are extracted with an extraction agent based on chlorinated hydrocarbon, whereupon from the extraction solution thus obtained an extract is separated, from which the extraction agent is removed and polyhydroxyalkanoates precipitate. Prior to the extraction of polyhydroxyalkanoates, components of the biomass other than polyhydroxyalkanoates are extracted from the biomass by means of an extraction agent based on alkyl alcohol having 2 to 4 carbon atoms in the chain, which is added to the biomass in a weight ratio of 1:0.