Mole fraction control of poly([R]-3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/HV) synthesized by Paracoccus denitrificans

Different substrate mixtures of acetic acid and valeric acid were used to synthesize copolymers of poly ([R] -3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB/HV) with Paracoccus denitrificans under N-limited conditions. A correlation between the substrate ratio and HV content was found in batch experiments, which seemed to be suitable to produce a number of defined copolymers. In fed-batch fermentation, such correlation could only be found with carbon substrate mixtures of very restricted composition. Due to the individual substrate consumption rates with this technique, a polymer with 16.5 mol.-% HV content [w/w] could be reproducibly synthesized. However, under N-limited chemostatic cultivation conditions it was possible to produce a spectrum of definitely composed copolymers (3.0%-46.3 mol.-% HV) from different mixtures of acetic acid and valeric acid.