Electro-membrane process for the separation of amino acids by iso-electric focusing

BACKGROUND: Amino acids (AAs) are usually produced commercially using chemical, biochemical and microbiological fermentation methods. The product obtained from these methods undergoes various treatments involving extraction and electrodialysis (ED) for salt removal and AA recovery. This paper describes an electro-membrane process (EMP) for the charge based separation of amino acids. RESULTS: Iso-electric separation of AAs (GLU-LYS) from their mixture, using ion-exchange membranes (IEMs) has been achieved by an efficient and indigenous EMP. It was observed that electro-transport rate (flux) of glutamic acid (GLU) at pH 8.0 (above its pl) was extremely high, while that for lysine (LYS) (pH 9.6) across the anion-exchange membrane (AEM) was very low, under similar experimental conditions. Under optimum experimental conditions, separation of GLU from GLU-LYS mixture was achieved with moderate energy consumption (12.9 kWh kg(-1)), high current efficiency (CE) (65%) and 85% recovery of GLU. CONCLUSIONS: On the basis of the electro-transport rate of AA and membrane selectivity, it was concluded that the separation of GLU-LYS mixture was possible at pH 8.0, because of the oppositely charged nature of the two amino acids due to their different pi values. Moreover, any type of membrane fouling and deterioration in membrane conductivity was ruled out under experimental conditions. This work clearly demonstrates the great potential of EMP for industrial applications. (C) 2010 Society of Chemical Industry