Electrodialysis (ED) shows good potential for downstream processing of acetate fermentation broths, to separate acetic acid while unreacted glucose and other nutrients are partially recycled back to the fermenter. With conventional anion- and cation-exchange membranes, higher current increased acetate flux, water flux, and energy consumption. Multiple ED stacks connected in series with unequal initial volumes for a batch process maximized acetate concentration in the concentrating stream to 134 g/L calcium-magnesium acetate (CMA) in the fermentation broth at PH 6.8. Back-transport of acetate from the product into the feed stream and water transport limit the maximum concentration possible. Cost of ED is about $295/ton acetate for the CMA broth.