Biosynthesis of polyhydroxyalkanoate copolymer by Cupriavidus necator H16 using γ-butyrolactone and sodium propionate as precursors

Abstract

Cupriavidus necator H16 was found capable of using crude fish oil and waste cooking oil as main carbon sources for poly(3-hydroxybutyrate) (PHB) production. In this study, the biosynthesis of value-added polyhydroxyalkanoate copolymer by C. necator H16 was investigated. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] was synthesized when γ-butyrolactone was added as a precursor to the culture medium; however, the content of the 4HB fraction in copolymer P(3HB-co-4HB) was low. The biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] was achieved by adding sodium propionate to the culture medium. P(3HB-co-3HV) containing 1.6 to 10.9 mol% 3HV fraction (in case of crude fish oil) and 1.2 to 11.5 mol% 3HV fraction (in case of waste cooking oil) was accumulated when supplemented propionate concentrations increased from 1 to 5 g/L. This study demonstrates the side-by-side production of P(3HB-co-4HB) and P(3HB-co-3HV) from crude fish oil and waste cooking oil by Cupriavidus necator H16. We establish a dose–response trade-off between precursor level, copolymer composition (4HB/3HV), and productivity (CDW, PHA%), thereby defining a practical operating window for composition-tunable PHAs from waste lipids.