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Zymomonas mobilis cells were immobilized with a novel Fe 2 O 3 -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 ) Fe 2 O 3 . The modified PVA-immobilized cells could be utilized for more than 20 days without losing their activity. [ABSTRACT FROM AUTHOR]

Concentration of ethanol from the fermentation broth is an energy-intensive process. Very high gravity (VHG) process with modified polyvinyl alcohol-immobilized Zymomonas mobilis cells integrated with in situ bioethanol removal via vacuum membrane distillation (VMD) was proposed to mitigate product inhibition effects in VHG fermentation. The proposed VHG + VMD system, at 300 g/L glucose loading, produced 127.4 g/L (16.1% v/v) ethanol, at 63.7 g/L−h productivity and 84.9% glucose conversion rate, which is the highest in reported literature. [ABSTRACT FROM AUTHOR]