Simultaneous purification and immobilization of Aspergillus niger xylanaseon the reversibly soluble polymer Eudragit (TM) L-100

The non-covalent immobilization of a commercial preparation of xylanase fro m A. niger was carried out on a reversibly soluble-insoluble enteric polyme r Eudragit(TM) L-100. The immobilization of the xylanase activity by adsorp tion was simultaneously accompanied by removal of cellulase activity since the latter did not bind to the polymer. Thus, the soluble enzyme derivative may be useful for treatment of paper pulp bleaching in paper industry. The immobilized xylanase retained 60% of its activity toward xylan as the subs trate. No change was observed in the pH optimum (5.5) of the enzyme upon im mobilization. Only marginal increase in the K-m of the free enzyme (3.6 mg ml(-1) to 5.0 mg ml(-1)) upon immobilization on the soluble polymer reflect ed that the enzyme-substrate binding continues to be efficient in spite of the macromolecular nature of the substrate. Fluorescence spectroscopy and U V difference spectroscopy were used to probe the change(s) in the enzyme st ructure upon immobilization. This change in structure was correlated with t he "effcctiveness factor" of the enzyme activity. CD spectra also showed th at the enzyme undergoes drastic changes in the structure. (C) 2000 Elsevier Science Inc. All rights reserved.