Production of Polyhydroxyalkanoates from Crude Glycerol Using Recombinant Escherichia coli

Abstract

© 2014, Springer Science+Business Media New York. The high production cost of bio-based plastic polyhydroxyalkanoates (PHAs) limits their use as commercial products. Thus, systems for PHAs production from waste substrates could reduce production costs. Crude glycerol is a by-product of biodiesel fuel production and thus represents an inexpensive, abundant and promising carbon source for production of valorized fermentation products. In this study, industrial crude glycerol by-product from palm oil biodiesel production was used as the carbon source for production of PHAs by recombinant Escherichia coli. Crude glycerol supplemented at 1–5 % (v/v) supported production of poly(3-hydroxybutyrate) (P(3HB)) in E. coli-ABC<inf>Ah</inf>, which harbors the PHA synthetic genes for β-ketothiolase (PhaA<inf>Re</inf>), acetoacetyl-CoA reductase (PhaB<inf>Re</inf>) of Ralstonia eutropha and Polyhydroxyalkanoate (PHA) synthase (PhaC<inf>Ah</inf>) of Aeromonas hydrophila. The highest P(3HB) content and productivity of 14 wt% of cell dry weight and 0.6 g/L, respectively, were obtained at 1 % (v/v) glycerol concentration. Production of P(3HB-co-3-hydroxyhexanoate) (P(3HB-co-3HHx)) was achieved using E. coli-ABC<inf>Ah</inf>J<inf>Ah</inf>, harboring genes for PhaA<inf>Re</inf>, PhaB<inf>Re</inf>, PhaC<inf>Ah</inf>, and the (R)-specific enoyl-CoA hydratase (PhaJ<inf>Ah</inf>) of A. hydrophila. This led to the copolymer content of 3 wt% of cell dry weight with 1 mol% of 3HHx. Molecular weight and degradation temperature of the polymers were in the range of 110–130 kDa and 295–299 °C, respectively. These results indicated that crude glycerol could be an attractive carbon source for economical production of PHAs with properties for industrial application.