Analysis of the performance of a continuous membrane bioreactor with cell recycling during ethanol fermentation

The effects of the introduction of cell recycling on ethanol productivity were examined for a continuous membrane fermenter-separator (CMFS) with continuous removal of ethanol by pervaporation. Modifications of the Ghose-Tyagi specific growth rate model and the Luedeking-Piret production model were used to formulate and simulate the CMFS model. The effects of pervaporation for systems with and without a cell separator were compared in terms of yeast cell density, substrate utilization, ethanol concentration in the fermentation broth and productivity. The results demonstrate that the elimination of cell wash-out allows the CMFS with cell separator unit to operate at a very high value of dilution rate and increases the productivity of ethanol at the same value of the pervaporation factor (PF) compared with a system without cell separator. An increase in the value of PF always results in an increase in ethanol productivity. (C) 1998 published by Elsevier Science S.A.