Application of the Plackett-Burman statistical design to optimize poly(â-hydroxybutyrate) production by Ralstonia eutropha in batch culture

Ralstonia eutropha accumulates poly(â-hydroxybutyrate) up to 80% of its dry weight (as a carbon and energy source) and is the best-known PHB producer. Although PHB has many potential applications in medicine, veterinary practice, agriculture and surgery, its high cost limits the widespread use of it. The recent researches have focused on reducing these costs by optimizing fermentation process. In this study the Placket Burman experimental design was used to test the relative importance of medium components and process variables on cell growth and PHB production. The optimum values of the variables, selected as the best conditions for further studies in the development of a low cost and effective fermentation process for PHB production, were as follows: initial fructose concentration, 15 g/l; C/N ratio, 7.4; shaking rate, 200 rpm; fermentation time, 40 h; temperature, 30°C; seed age, 15 h .