Batch experiments were conducted in order to estimate the accumulation percentages, rates and yields of PHAs in the enriched culture and all isolates. Both synthetic wastewater and acidified OMW were used as substrates for PHAs production. Batch experiments were conducted at room temperature with continuous air supply provided through sterile filters of 0.2 m pore size, under oxygen sufficient (DO > 2 ppm) and oxygen limited conditions(DO < 2 ppm), and constant stirring at 250 rpm. Total suspended solids (TSS), cell dry mass (CDM), determined as VSS, Volatile Fatty Acids (VFAs) concentration and pH were monitored versus time,while the PHAs content in biomass was estimated at the beginning and end of each experiment.