Production of xylo-oligosaccharides from agro-industrial residues using immobilized Talaromyces thermophilus xylanase

Abstract

Talaromyces thermophilus stolk a thermophilic fungus isolated from soil samples collected in Tunisia. The single xylanase from this strain was purified to complete homogeneity. Several enzyme immobilization methods were then tested and compared for residual enzyme activity. The most efficient immobilization was achieved by gelatin (10%) using glutaraldehyde as a bifunctional agent. This method gave an immobilization yield of 98.8% and a xylanase activity recovery of 99.2%. The immobilized enzyme exhibited a shift in the optimal pH from 7 to 8 but the optimal temperature of activity was not affected. The immobilized enzyme retained about 94.0% of its initial catalytic activity even after being used during 13 successive cycles of hydrolysis at 50 °C. The main hydrolysis products yielded from xylan were xylobiose and other xylo-oligosaccharides such as xylotriose. The immobilized enzyme was then used for the large-scale continuous production of xylobiose, starting from the hemicellulose of lignocellulosic material waste as wheat bran. The co-immobilization of the β-xylosidase and the xylanase of T. thermophilus allowed the increase of xylan saccharification efficiency by liberation of xylose, proving the synergistic action of both enzymes.