Migration of Amino Acids in Bipolar Membrane Electrodialysis Process of Lactic Acid Fermentation Broth

Migration of amino acids concurrently with lactic acid from the feed cell to the acid cell in the three-compartment bipolar-membrane electrodialysis (BMED) process of lactic acid fermentation broth influences the purity of recovered lactic acid. Amino acid migration phenomenon and its rules were investigated in the bipolar-membrane electrodialysis process of lactic acid fermentation broth. The results showed that migration velocity of amino acid was mainly influenced by amino acid concentration, the difference between its pI and the environmental pH, the selectivity of anion exchange membrane to the amino acid anion, and the ionic mobility of amino acid anion. Based on this migration rule, an ionic migration velocity calculation model was developed and validated by comparing it with practical BMED process. The result of a process applying the calculation model showed that migration rate of total amino acids being 32.5% was 60.7% lower than the controlled experiment of 82.6%. Higher lactic acid purity via BMED could be achieved by regulating hydrogen leakage to control the pH in the feed cell and improving the selectivity of anion exchange membrane to lactic acid anion.