In this study, we considered a bioprocess optimization problem for continuous ethanol fermentation with cell recycling. The aim of the optimization problem was to obtain the maximum overall productivity and conversion subject to the interval inequality constraints for residual glucose concentration and the total amount of glucose supplied. The residual glucose not only leads to a loss of revenue but also can create environmental problems, such that employing both constraints has benefits for both operating costs and environmental impact. A fuzzy goal attainment method was introduced to the multiobjective problem in order to obtain a trade-off solution. From the computational results, the overall productivity of the continuous fermentation process with cell recycling allowed for a higher dilution rate, such that the overall productivity was about 7.3-fold higher than that of a continuous mixed-flow fermentation process.