Production of poly(3-hydroxybutyrate) from a complete feedstock derived from biodiesel by-products (crude glycerol and rapeseed meal)

A combination of crude glycerol and rapeseed meal from biodiesel production can be utilised to produce a complete microbial feedstock for value-added chemicals production. In this study, rapeseed meal was transformed into a solution rich in free amino nitrogen and was used as a nitrogen source, in combination with crude glycerol as carbon source, to produce poly(3-hydroxybutyrate) (PHB). Using Cupriavidus necator in fed-batch fermentation, PHB concentration at 24.75 g/L with a productivity of 0.21 g·L−1 h−1, and a yield of 0.32 g-PHB/g-glycerol were obtained. Based on these results, a process for bioconversion of biodiesel by-products to PHB is proposed. In this process, 3.41 L of crude glycerol and 0.72 kg of rapeseed meal are all that is required for the production of 1 kg of PHB. The study demonstrates clearly that a complete microbial feedstock with no requirement for further nutrient supplements can be derived directly from the principal by-products of a conventional biodiesel process.