ADSORPTION OF KLUYVEROMYCES-MARXIANUS PECTINASE ON CM-SPEHADEX GELS

New results are presented on the equilibria and kinetics of the ion ex change onto CM-Sephadex of polygalacturonase (pectinase) produced by t he fermentation of Kluyveromyces marxianus. It is found that the equil ibrium behavior follows the form of the Langmuir isotherm; the equilib rium is strongly affected by pH. High partitioning onto the ion-exchan ge matrix, with good retention of enzyme activity, is achieved in the pH range 3.5-5.0, and this can be qualitatively explained in terms of simple models for protein adsorption by ion exchange. The kinetics of ion exchange is modeled by assuming that the transfer resistances can be lumped into a single coefficient, and the results show that this gi ves a reasonable description of the adsorption kinetics. Under optimum conditions protein adsorption is enhanced by electrostatic effects an d is extremely fast, and it is suggested that in these circumstances e xternal mass transfer resistance is significant. At pH values close to the isoelectric point, electrostatic interactions are weak and intrap article diffusion is rate-limiting: pore-blocking by adsorbed proteins appears to be important under these conditions. The results also prov ide the basis for an efficient single-step purification scheme.