CROSS-LINKED MACROPOROUS CHITOSAN ANION-EXCHANGE MEMBRANES FOR PROTEIN SEPARATIONS

Macroporous chitosan membranes with controlled pore sizes and good mec hanical properties were prepared and crosslinked with ethylene glycol diglycidyl ether to increase their chemical stability. Because of thei r amine groups, they can serve as anion-exchangers (with an ion-exchan ge capacity as high as 0.83 meq/g dry cross-linked membrane) and can b e employed for protein separations in the ion-exchange mode. At pH<7, their surface is positively charged. and they can adsorb proteins with a pI<6 at appropriate pHs. Five proteins, namely ovalbumin (pI=4.6), human serum albumin (pI=4.8), soybean trypsin inhibitor (pI=4.5), lyso zyme (pI=11) and cytochrome C (pI=10.6) were selected as model protein s to investigate their adsorption on the chitosan membranes. Relativel y high dynamic capacities were achieved at a flow rate of 2 ml/min, na mely 11.6, 19 and 20.8 mg/ml membrane for human serum albumin, ovalbum in and soybean trypsin inhibitor, respectively. These proteins could b e efficiently recovered (91-98%) from the membranes using a 1 N NaCl i n 0.02 N sodium phosphate solution (pH 6) as eluant. Protein separatio ns were performed from binary mixtures (ovalbumin-lysozyme, human seru m albumin-cytochrome C, and soybean trypsin inhibitor-cytochrome C), a nd high purity products (similar to 99%) obtained in a single pass. Th ese membranes showed high stability and reproducibility. (C) 1998 Else vier Science B.V. All rights reserved.