The combined fermentation of sludge from the secondary sedimentation tank of municipal wastewater treatment plants and food waste enables not only waste reduction, but also the acquisition of volatile fatty acids (VFAs) for the biosynthesis of polyhydroxyalkanoates (PHAs). To better understand variables influencing the production of VFAs and PHAs, this study considered anaerobic fermentation of VFAs under different pH conditions. The production of VFA was the highest at an initial pH of 9.0, reaching 25,934 +/- 1,485 mg COD/L and a VFAs/SCOD ratio of 0.61 +/- 0.04. When the fermentation liquid was used as a carbon source for PHA biosynthesis, continuous pulsed feeding resulted in the highest PHA synthesis rate of 64.5 +/- 1.8%, while the culture receiving a one-time feeding had the lowest rate of only 51.5 +/- 2.0%. (C) 2012 Elsevier Ltd. All rights reserved.