Integration of charged membrane into perstraction system for separation of amino acid derivatives

The integration of a charged membrane into a perstraction system for high selective separation is reported. A mixture of N-(benzyloxycarbonyl)-L-aspartic acid (ZA), L-phenylalanine methyl ester (PM), and N-(benzyloxycarbonyl)-L-aspartyl-L-phenylalanine methyl ester (ZAPM) was used as the model solution. The aqueous phase containing ZA, PM, and ZAPM was adjusted to pH 6 and was contacted with tert-amyl alcohol through a charged membrane. Seven different ion-exchange membranes and two different microfiltration membranes were tested for the separation system. Only ZAPM could permeate into the organic phase through SELEMION AMV and ASV. The separations between ZA and ZAPM and between PM and ZAPM were performed by biphasic extraction and electrostatic rejection, respectively. The permeabilities of ZAPM were higher than those of PM for all experiments using the ion-exchange membranes, although the molecular weight of ZAPM is larger than that of PM. The membrane that had a smaller pore size showed higher ZAPM selectivity. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 162-167, 1997.