Immobilization and stabilization of commercial β-1,4-endoxylanase Depol™ 333MDP by multipoint covalent attachment for xylan hydrolysis: Production of prebiotics (xylo-oligosaccharides)

The commercial enzyme Depol (TM) 333MDP (D333MDP) was immobilized by multipoint covalent attachment onto 10% cross-linked agarose beads support highly activated with aldehyde groups. The enzyme immobilization process was very efficient, retaining 86% of its initial catalytic activity. Thermal stability of the immobilized D333MDP biocatalysts varied according to the incubation time of the enzyme-support. The optimal immobilized biocatalyst was produced after 24 h of incubation under alkaline conditions and longer incubation times resulted in a loss of stability. The optimal immobilized biocatalyst was 60- and 50-fold more stable at pH 5.5 and pH 7 at 50 degrees C than the soluble enzyme, respectively. Activity and stability at pH 5.5 were enhanced when the optimal immobilized biocatalyst was modified by chemical amination of the enzyme surface. The chemical amination of the immobilized enzyme surface was 5-fold more stable at pH 5.5 and 50 degrees C compared with the unmodified immobilized biocatalyst. The best immobilized biocatalysts (containing 100 UI/g of support) were evaluated in the beechwood xylan hydrolysis reaction at 50 degrees C and pH 5.5. 80% of the reducing sugars were released after 6 h of hydrolysis with the aminated biocatalyst. Xylan hydrolysis reaction with the aminated biocatalyst was 80% faster than with the non-aminated one. The final composition of the xylooligosaccharides (XOS) obtained was identified and quantified by HPAEC-PAD which showed it was composed of 90% of xylobiose and 5% of xylotriose and xylose. The aminated immobilized-stabilized biocatalyst was used for four cycles of hydrolysis with no loss of catalytic activity, resulting in highly active and stable derivative suitable for industrial processes.