in this study, a bioprocess optimization problem was considered for a multiple-stage extractive fermentation, including cell recycling, to produce lactic acid. The aim of the optimization problem is to obtain the maximum overall productivity, conversion and yield simultaneously, so that the optimization problem is formulated as a multi-objective optimization procedure. The fuzzy goal attainment method was introduced to the multi-objective optimization problem in order to obtain a trade-off solution. The approach was also employed to determine the optimal design for two simplified continuous fermentation processes. From the computational results, the overall productivity for the fermentation processes including cell recycling, enabled a higher dilution rate so that the overall productivity was ca. thirteen-fold higher than that of the continuous fermentation process without cell recycling.