Glycerol, a byproduct of the biodiesel industry, can be used by bacteria as an inexpensive carbon source for the production of value-added biodegradable polyhydroxyalkanoates (PHAs). Burkholderia cepacia ATCC 17759 synthesized poly-3-hydroxybutyrate (PHB) from glycerol concentrations ranging from 3% to 9% (v/v). Increasing the glycerol concentration results in a gradual reduction of biomass, PHA yield, and molecular mass (M-n and K-w) of PHB. The molecular mass of PHB produced utilizing xylose as a carbon source is also decreased by the addition of glycerol as a secondary carbon source dependent on the time and concentration of the addition. H-1-NMR revealed that molecular masses decreased due to the esterification of glycerol with PHB resulting in chain termination (end-capping). However, melting temperature and glass transition temperature of the end-capped polymers showed no significant difference when compared to the xylose-based PHB. The fermentation was successfully scaled up to 200 L for PUB production and the yield of dry biomass and PHB were 23.6 g/L and 7.4 g/L, respectively. (C) 2009 American Institute of Chemical Engineers Biotechnol. Prog., 26: 424-430, 2010