Electrodialysis as a useful technique for lactic acid separation from a model solution and a fermentation broth

A two-stage electrodialysis (ED) method was used for lactic acid recovery. In the first step sodium lactate was concentrated with desalting electrodialysis using ion exchange membranes Ralex (Mega, Czech Republic). The second step was the electroconversion of sodium lactate to lactic acid by electrodialysis with bipolar membranes (EDBM) Neosepta (Tokuyama Corp., Japan). The lactic acid was recovered from model solutions and from real fermentation broth as well. The trials with model solutions were focused on determination of the suitable conditions for electrodialysis experiments and on investigation of the time course under different conditions. The fermentation broth from lactic acid fermentation had to be pretreated before electrodialysis experiments. The pretreatment consisted of ultrafiltration, decolourisation and removing of multivalent metal ions. In the first ED step the final lactate concentration of 175 g/l was obtained and afterwards the final lactic acid concentration of 151 g/l was reached in the second ED step.