Continuous solvent production by Clostridium beijerinckii BA101 immobilized by adsorption onto brick

The performance of a continuous bioreactor containing Clostridium beijerinckii BA101 adsorbed onto clay brick was examined for the fermentation of acetone, butanol, and ethanol (ABE). Dilution rates from 0.3 to 2.5 h^-1 were investigated with the highest solvent productivity of 15.8 g l^-1 h^-1 being obtained at 2.0 h^-1. The solvent yield at this dilution rate was found to be 0.38 g g^-1 and total solvent concentration was 7.9 g l^-1. The solvent yield was maximum at 0.45 at a dilution rate of 0.3 h^-1. The maximum solvent productivity obtained was found to be 2.5 times greater than most other immobilized continuous and cell recycle systems previously reported for ABE fermentation. A higher dilution rate (above 2.0 h^-1) resulted in acid production rather than solvent production. This reactor was found to be stable for over 550 h. Scanning electron micrographs (SEM) demonstrated that a large amount of C. beijerinckii cells were adsorbed onto the brick support.