Downstream processing of acetate fermentation broths by nanofiltration

Acetate can be separated from fermentation broths and partially purified by nanofiltration (NF). Membrane performance was a function of pressure, pH, concentration of acetate, temperature, and the presence of other media components. With Nitto-Denko's NTR729 membrane, average acetate rejection was 60%, glucose rejection was 99%, and flux was 15 L/m(2)/h at 200 psig, 30 degrees C, pH 5.6, and 20 g/L acetic acid. The best downstream strategy is to clarify the fermentation broth by microfiltration (MF), recycle the cells for improving fermenter productivity, nanofilter the cell-free broth, and then evaporate the permeate. The cost of ceramic MF and NF purification is about $66/t acetate, compared to the cost of potassium acetate ($950/t) or calcium-magnesium acetate ($700/t).