| 摘要 |
High molecular weight copolymers containing 3-hydroxybutyrate residues, i.e. units of the formula -O.CH(CH3).CH2.CO- and up to 50 mole % of residues of other hydroxy acids, viz units of the formula -O.CR<1>R<2>.(CR<3>R<4>)n.CO- where n is 0 or an integer and, if n = 1 and R<2>, R<3>, and R<4> = H, R<1> is not methyl. The copolymers are made microbiologically: for part of the cultivation the micro-organism is under conditions such that polymer is accumulated, e.g. by limitation of a nutrient, e.g. nitrogen source, required for growth but not polyester accumulation. For at least part of this period of polymer accumulation the substrate is an acid or a derivative thereof that gives the comonomer units. Propionic acid, which gives polymers where n = 1, R<2>=R<3>=R<4>=H and R<1> = C2H5, is the preferred acid. |
