Poly-b -hydroxybutyrate (PHB) production by halophilic mixed consortia has great advantage in cost. PHB production by the two-step production process using halophilic activated sludge cultured from estuary sediment was investigated. During the continuous 300 d

the ability of PHB storage at different F/F was assessed from the performance of the long-term tests

experiments of PHB production and the observed kinetics. The ratio of feast to famine (F/F) as an important parameter directly affected the capacity of the PHB-storing of halophilic activated sludge. At a high F/F the non PHB-storing bacteria became dominant in the enrichment reactor

while a low F/F was in favor of the selection and enrichment of PHB-storing bacteria. Moreover

the culture selected at F/F less than 0.33 showed the best PHB-storing capacity with a PHB content of 46.7% cell dry weight and a PHB yield of 0.358 mg PHB·(mg Ac)-1. The results obtained in the study provided a guidance to the production of PHB by halophilic activated sludge.