Electrodialysis of acetate fermentation broths

Electrodialysis (ED) shows good potential for downstream processing of acet ate fermentation broths, to separate acetic acid while unreacted glucose an d other nutrients are partially recycled back to the fermenter. With conven tional anion- and cation-exchange membranes, higher current increased aceta te flux, water flux, and energy consumption. Multiple ED stacks connected i n series with unequal initial volumes for a batch process maximized acetate concentration in the concentrating stream to 134 g/L calcium-magnesium ace tate (CMA) in the fermentation broth at PH 6.8. Back-transport of acetate f rom 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 br oth.