Production of Polyhydroxyalkanoates from Crude Glycerol Using Recombinant Escherichia coli.

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, which harbors the PHA synthetic genes for β-ketothiolase (PhaA), acetoacetyl-CoA reductase (PhaB) of Ralstonia eutropha and Polyhydroxyalkanoate (PHA) synthase (PhaC) 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-ABCJ, harboring genes for PhaA, PhaB, PhaC, and the ( R)-specific enoyl-CoA hydratase (PhaJ) 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. [ABSTRACT FROM AUTHOR]