A novel rotating wide gap annular bioreactor (Taylor-Couette type flow) for polyhydroxybutyrate production by Ralstonia eutropha using carob pod extract.

An annular bioreactor (ABR) with wide gap was used for PHB production from Ralstonia eutropha. Hydrodynamic studies demonstrated the uniform distribution of fluid in the ABR due to the Taylor-Couette flow. Thereafter, the ABR was operated at different agitation and sparging rates to study its effect on R. eutropha growth and PHB production. The ABR operated at 500 rpm with air sparge rate of 0.8 vvm yielded a maximum PHB concentration of 14.89 g/L, which was nearly 1.4 times that obtained using a conventional stirred-tank bioreactor (STBR). Furthermore, performances of the bioreactors were compared by operating the reactors under fed-batch mode. At the end of 90 h of operation, the ABR resulted in a very high PHB production of 70.8 g/L. But STBR resulted in a low PHB concentration of 44.2 g/L. The superior performance was due to enhanced oxygen and nutrient mass transfer in the ABR.