The isolated strains were grown in the basal medium described above, containing both nitrogen and carbon sources, under sterile conditions. The medium was thermally sterilized for 20 min at 1 bar and 121◦C and air supply was provided to the cultures via sterile filters with 0.2 m pore size. When nitrogen was fully consumed the microbial biomass was left to settle and then used as inoculum in the batch experiments.
As for the ‘enriched’ culture, microbial biomass was collected and used as inoculum at the end of the carbon limitation phase, i.e.growth of biomass by consuming intracellular PHAs and
extracellular nitrogen source in the form of (NH4)2SO4