Crosslinked xylan as an affinity adsorbent for endo-xylanases.

In order to facilitate the purification of xylanases from Aspergillus niger, an affinity adsorbent has been developed from oat spelts xylan. A suitable adsorbent was only obtained by crosslinking oat spelts xylan with epichlorohydrin in water but not in ethanol or ethanol-water mixtures. After some initial degradation of the adsorbent (approximately 4%), no significant biodegradation was measured with a reused adsorbent. Up to 60% of the xylanase activity from an Aspergillus niger enzyme mixture (50 mU/ml) was adsorbed at pH 4 (50 mm sodium acetate buffer). The degree of adsorption to crosslinked xylan of four fractions of this preparation, previously separated by DEAE-Biogel A chromatography, varied between 40 and 90%.

Adsorption was strongly dependent on pH and ionic strength and desorption was easily accomplished by an increase in ionic strength. In addition to xylanases, polygalacturonases were also adsorbed to the matrix. No significant adsorption of β-d-xylosidase, α-l-arabinofuranosidase, β-d-galactosidase, β-(1,4)-galactanase,
β-(1-36)-d-galactanase
or cellulase activities was found.