Abstract: The present invention is directed to a copolymer containing a 3-hydroxybutyrate (3HB) unit and a 3-hydroxyhexanoate (3HHx) unit, a three-component copolymer containing at least a 3-hydroxybutyrate (3HB) unit and a 3-hydroxyhexanoate (3HHx) unit, and a four-component copolymer containing at least a 3-hydroxybutyrate (3HB) unit and a 3-hydroxyhexanoate (3HHx) unit. The use of a microorganism of the genus Aeromonas according to the present invention makes it possible to produce a wide variety of plastic materials ranging from rigid plastics to elastic plastics by selecting copolymer components and adjusting their composition.

Abstract: The present invention is directed to a copolymer containing a unit represented by Formula (1): ##STR1## wherein Y represents a hydrocarbon residue having 1 to 13 carbon atoms which may have 1 to 4 double bonds. A method for production thereof comprises the steps of culturing microorganisms of the genus Pseudomonas under limitation of nutrients other than carbon sources using a medium containing long-chain fatty acids having 14 to 22 carbon atoms or lower alcohol esters thereof, or triglycerides comprising long-chain fatty acids having 14 to 22 carbon atoms as carbon sources; washing the bacterial cells after completion of cultivation; extracting the bacterial cells; and recovering a polyester from the extracts.