Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-3HV) production from propionic acid and biodiesel glycerol by mutant strains of Pandoraea sp. MA03

Abstract

The polyhydroxyalkanoates (PHAs) are biodegradable polyesters that are synthesized intracellularly and deposited as granules in bacterial cultures in the presence of excess carbon source and a growth limiting nutrient. These biopolymers are attractive substitute for petrochemical-based plastics due to their similar material properties to various thermoplastics and elastomers. The poly-3-hydroxybutyrate (P3HB) is the most common type of PHAs and its characteristics such as high cristallinity, stiffness, brittleness and low extension to break limit its application range. The mechanical and thermal properties of P3HB can be improved by incorporating co-monomers like 3-hydroxyvalerate (3HV). One factor that can lead to higher cost to PHAs production is the cost of carbon feedstocks for bacterial cultures. Many agricultural and industrial byproducts have been considered for PHAs production and among them the biodiesel glycerol has becoming an interesting alternative. In this project, will be obtained mutants of Pandoraea sp. MA03 that are unable to grow on propionic acid but still produce P3HB-co-3HV from this precursor and biodiesel glycerol as a carbon source. The most promising mutant strain on P3HB-co-3HV production will be selected for bioreactor experiments, which will evaluate the best dissolved oxygen concentration, biodiesel glycerol/propionic acid rates and specific feed rate values. Furthermore, cultivation at a 42-liter scale bioreactor will be conducted for P3HB-co-3HV production via high-cell-density fed-batch fermentation.