Synthesis of poly-hydroxyalkanoates from activated sludge under various oxidation-reduction potentials

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The production of poly-hydroxyalkanoates (PHA) from the activated sludge subjected to conditions with various oxidationreduction potentials (ORPs) was investigated. By controlling the dissolved oxygen concentration in the cultural media, the ORP were kept at preset levels of −20, −10, 0, and +10 mV. With glucose as the dedicated carbon source, we have demonstrated a correlating relationship with the ORP’s in the culture media to the PHA accumulation rate, the PHA production-yield, cell growth rate, glucose uptakes and 3-hydroxybutyrate to 3-hydroxyvalerate (HB/HV) mole ratios in the PHA copolymers. The highest PHA production yield of 0.26 g/g with HB/HV mole ratio of 8.03 was achieved at +10 mV ORP. We concluded that oxygen plays an important role in PHA accumulation and HB/HV mole ratio activated sludge-to-copolymer PHA conversion process.