Production of high ethanol concentrations from glucose using Zymomonas mobilis entrapped in a Vertical Rotating Immobilized Cell Reactor

Long-term continuous ethanol production of up to 80 g l with a volumetric ethanol productivity of 63 g l h was maintained for more than 72 days using a Vertical Rotating Immobilized Cell Reactor containing the bacterium Zymomonas mobilis. Continuous production of higher ethanol concentrations was unsuccessful due to an inhibition of cell growth by long exposure to high ethanol concentrations. However, an ethanol concentration as high as 120 g l and a volumetric ethanol productivity of 13 g l h were achieved in a repeated-batch fermentation system using the same bioreactor. By a simple washing operation at the end of each run, immobilized biomass could be effectively regenerated and used to carry out more than 10 successive fermentation cycles