Purpose : The main objective of the present study is to assess and improve fermentation conditions to produce polyhydroxyalkanoates (PHAs), such as the homopolymer polyhydroxybutyrate (PHB) and the copolymer polyhydroxybutyrate-co-hydroxyvalerate (PHBV), from renewable and inexpensive industrial waste by wild type Cupriavidus necator.
Methods : Untreated residual glycerol, a byproduct generated by biodiesel industry, was used as the main carbon source by wild type C. necator . The bacterial adaptation stage, the glycerol concentration and other medium components were adjusted to enhance the PHB production. Fed batch fermentation with a pulse feeding strategy of propionic acid solution was employed for PHBV production.
Results: C. necator , previously adapted to glycerol utilization, was able to accumulate PHB up to 4.1 g/l under optimal substrate concentration conditions. The bacterium could also synthesize up to 3.4 g/l PHBV, with a mole fraction of 3-hydroxyvalerate (HV) up to 12 % by fed-batch fermentation with a pulsed propionic acid feed strategy.
Conclusion: This is the first report on the use of residual glycerol as ideal feedstock for PHA production by native C. necator strain.