Immobilization of Zymomonas mobilis with Fe2O3-modified polyvinyl alcohol for continuous ethanol fermentation

Zymomonas mobilis cells were immobilized with a novel Fe2O3-modified polyvinyl alcohol (PVA) matrix to perform continuous ethanol fermentation with very high efficiency. The key operating parameters, such as glucose feeding concentration, dilution rate, and cells loading were optimized to achieve high bioethanol production performance at a high dilution rate and high glucose utilization efficiency. The optimal conditions for ethanol fermentation with the modified PVA immobilized cells were determined as: cell loading, 40% (w/v); glucose feeding concentration, 125 g/L; hydraulic retention time (HRT), 2 h (or 0.5 h⿿1 dilution rate). The bioethanol productivity was nearly doubled (31.09 g/L/h) when the PVA-immobilized cells were modified with 1% (w/v) Fe2O3. The modified PVA-immobilized cells could be utilized for more than 20 days without losing their activity.