Production of poly-beta-hydroxybutyric acid by microorganisms accumulated from river water using a two-stage perfusion culture system

The perfusion culture system using a shaken ceramic membrane flask (SCMF) w as employed to accumulate microorganisms separated from river water and to produce poly-beta-hydroxybutyric acid (PHB). Using a two-step culture metho d with a single SCMF, river microorganisms were cultured by separately feed ing four representative carbon sources, n-propanol, lactic acid, methanol, and formic acid. After 140 h culture, the cell concentration and PHB conten t respectively reached 43 g/l and 35% when a propanol medium was fed. Using a two-stage perfusion culture with twin SCMFs, the seed cell mass was incr eased in the first SCMF and then supplied to the second flask for PHB produ ction. As a consequence, the cellular PHB content rose to 51% in the second SCMF, while the cell concentration gradually increased to 25 g/l after 175 h perfusion culture. These results demonstrated the utility of the two-sta ge perfusion culture system for developing a cheap means of producing PHB c oincident with wastewater treatment.