Synthesis of Polyhydroxyalkanoates by Hydrogen-Oxidizing Bacteria in a Pilot Production Process

The synthesis of polyhydroxyalkanoates (PHAs) was scaled up to pilot production in a 150-L fermenter on sugars (fructose and glucose) and purified and crude glycerol in a culture of the wild-type strain Cupriavidus necator B-10646. Over 60 h of cultivation, a cell concentration of 150-160 g/L was obtained on purified glycerol and glucose; cultivation on fructose and crude glycerol resulted in a cell concentration of 130 ± 10 g/L. Polymer content and yield coefficients for the biomass were similar on all substrates (80-85 wt % and 0.29-0.33 kg biomass/kg carbon substrate, respectively). Copolymers poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and terpolymers poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) having a decreased degree of crystallinity (36-46%) were first synthesized in the scaled-up process using C. necator B-10646 cultivated on glycerol. These results will provide the basis for scaling-up PHA synthesis in an organotrophic C. necator B-10646 culture.