Charged fusions for selective recovery of beta-galactosidase from cell extract using hollow fiber ion-exchange membrane adsorption

We explored the use of charged fusions for selective recovery of beta-galactosidase from cell extract using a low-cost, easily scaled, fast, charge-based separation technique-ion exchange on hollow fiber ion-exchange membranes (HFIEMs). The additional charges carried by a series of anionic fusion tails allowed selective binding and release of beta-galactosidase from Escherichia coli cell extract using the HFIEM cartridge. The purification factors increased with fusion length. The beta-galactosidase was recovered in active form. For the longest fusion studied, more than sixfold enrichment in specific activity was attained. The specific activity of the recovered fraction is comparable with that of commercial wild-type beta-galactosidase and affinity-purified fusion protein. (c) 1993 John Wiley & Sons, Inc.