Utilization of biodiesel waste as a feedstock for the production of polyhydroxybutyrate by Cupriavidus necator

Abstract

This study aimed to investigate the potential of using wastewater and crude glycerol from biodiesel refinery to produce polyhydroxyalkanoates (PHAs) through fermentation of Cupriavidus necator TISTR 1095. The result indicates that crude glycerol yielded high cell growth (35 to 37 g/L) and poly-3-hydroxybutyrate (PHB; 17.85 to 19.98 g/L). However, no cell growth obtained from biodiesel-wastewater due to high Na⁺ presented. Among medium and experimental factors influencing PHB accumulation, crude glycerol, (NH₄)₂SO₄ and trace element concentration revealed significant effects (P<0.1). Their optimal values were 60 g/L crude glycerol, 1.32 g/L (NH₄)₂SO₄ and 2.0 g/L trace element. Under these optimal conditions, the strain TISTR 1095 produced the highest biomass (46.25±2.10 g/L) and PHB concentration of 24.98±1.87 g/L with PHB content of 54.01% of DCW. Effect of experimental conditions including aeration rate and agitation speed as well as sterile condition on PHB accumulation was also studied. The optimal aeration rate (2 vvm) and agitation speed (150 rpm) under septic condition during cultivation gave slightly increase of biomass and PHB. The maximum biomass (46.96±0.28 g/L) and PHB concentration of 25.32±0.20 g/L (53.92% of DCW) was achieved in 20-L fermentor. Moreover, the purified PHB from C. necator TISTR 1095 was partially characterized; their properties were similar to commercial PHB.

Key words: Biodiesel, Cupriavidus necator, glycerol, optimization,  polyhydroxybutyrate, poly-3-hydroxybutyrate (PHB).