Mixed matrix membranes for process intensification in electrodialysis of amino acids

BACKGROUND: Amino acids are valuable intermediates in the biobased economy for the production of chemicals. Electro-membrane processes combined with enzymatic modification have been investigated as an alternative technology for the fractionation of a mixture of amino acids with almost identical charge behavior. Up to now, the modification and subsequent separation were performed in two separate reactors. An interesting approach is the integration of both unit operations into one single device using mixed matrix membranes (MMMs) as platform for enzymatic conversion.

RESULTS: MMMs containing the enzyme glutamic acid decarboxylase (GAD, EC 4.1.1.15) Relizyme EP403/S as carrier were prepared showing satisfactory mechanical stability and enzymatic activity for L-glutamic acid conversion into γ-aminobutyric acid (GABA). ED with integrated MMM for simultaneous enzymatic decarboxylation of L-glutamic acid to GABA (33% conversion) and further separation of L-aspartic acid and unconverted L-glutamic acid from GABA was successful leading to current efficiency of 40% and low energy consumption of 3 kWh kg-1.

CONCLUSIONS: Together with the high mechanical stability obtained for the MMMs, this opens the route towards process intensification, combining enzymatic conversion and separation with electrodialysis in one integrated process for the successful isolation of amino acids for biorefinery applications.