In-situ combination of fermentation and electrodialysis with bipolar membranes for the production of lactic acid: continuous operation.

An experimental study was carried out to achieve a continuous integrated operation of fermentation and electrodialysis with bipolar membranes (EDBM). There need three steps to accomplish this experiment: (1) individual continuous fermentation; (2) individual continuous EDBM; (3) integrated operation of fermentation and EDBM under continuous condition. The results indicate that the maximum feed rate (fermenter can afford) is 0.24 L/h, which is also equal to the feed rate of the subsequent individual continuous EDBM. During continuous EDBM, the recovery ratio of lactate from the fermentation broth can reach 69.5% under a current density of 40 mA/cm(2). The net end concentration and total molar quantity for lactic acid can reach 1.46 mol/L and 2.18 mol, and for OH(-) are 1.32 mol/L and 1.70 mol, respectively. The integration can be achieved only under an initial alkali concentration of no less than 1 mol/L and a current density of no less than 30 mA/cm(2).