Production of xylooligosaccharides from xylan catalyzed by endo-1,4-β-D-xylanase-immobilized nanoscale carbon, silica and zirconia matrices

Abstract

Nanoscale materials of carbon, silica and zirconia were used to immobilize a recombinant endo-1, 4-β-D-xylanase (XynC) of B. subtilis KCX006. The adsorption of endo-1, 4-β-D-xylanase on nanomaterials of carbon, silica and zirconia followed the pseudo-second-order kinetic model. The activation energies for adsorption of endoxylanase on carbon, silica and zirconia nanomaterials were 9.94 kJ mol−1, 40.44 kJ mol−1 and 16.33 kJ mol−1 respectively. The recovered activity (RA) of endoxylanase immobilized on carbon, silica and zirconia nanomaterials was in the range of 52%–92%. The endoxylanase immobilized on zirconia nanoparticles showed maximum RA. All immobilized endoxylanase showed optimum activity at pH 6.6 similar to that of free/soluble endoxylanase. But compared to free endoxylanase, all immobilized endoxylanase had broad optimum temperature range (50–65 °C) for catalytic activity. The Michaelis-Menten constant (Km) increased for all immobilized endoxylanase due to substrate diffusion limit. The endoxylanase immobilized on above nanomaterials was used repeatedly for XOS production from xylan. All immobilized endoxylanase produced X2–X6 and substituted XOS similar to free endoxylanase from beechwood xylan and extracted crude xylans from sorghum and sugarcane bagasse. The endoxylanase immobilized on above nanoparticles did not lose activity after five batches of repeated use. The results showed that endoxylanase immobilized on carbon, silica and zirconia matrices would be useful for production of XOS by enzyme recycling.