A total limitation of the nitrogen source was achieved after 18 h of fermentation, extra ammonium sulphate (0.25 g/L) was added into system after 24 h to enhance cell metabolism. After 36 h of cultivation the CDW was quantified as 5.72 g/L with 41 wt% of PHA accumulation. Regarding the nitrogen evolution, the extra addition of nitrogen was completely consumed by the cells after 36 h of cultivation.