Synthesis and Properties of Degradable Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] Derived from Waste Fish Oil

The article presents the results of the first successful synthesis of degradable microbial copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate [P(3HB-<i>co</i>-3HV)] by the wild-type strain <i>C. necator</i> B-10646 using waste fish oil (WFO) obtained from the heads of <i>Sprattus sprattus balticus</i>. Samples of copolymers with 3HV monomer contents from 11.9 to 59.7 mol.% were synthesized with fractional and controlled feeding of potassium valerate, a precursor of 3HV monomers, into the bacterial culture. Samples synthesized on WFO with different contents of 3HV monomers had a reduced degree of crystallinity (36.5% and below), and close average molecular weight (390-573 kDa), with polydispersity of 2.6-3.0, and retained thermal stability, with a gap between the melting point and the thermal degradation temperature of over 100 °C. The thermal behavior of the samples, including the kinetics of exothermic crystallization and spherulite formation, was studied. Demonstrating the possibility of using WFO for the effective synthesis of P(3HB-<i>co</i>-3HV) with macroinclusions of 3HV monomers without deterioration of their properties is important for expanding the raw material base, reducing costs and increasing the availability of these promising bioplastics.