Abstract
β-xylosidases catalyse the hydrolysis of short chain xylooligosaccharides from their non-reducing ends into xylose. In this study we report the heterologous expression of Aspergillus oryzae β-xylosidase (XylA) in Pichia pastoris under the control of the glyceraldehyde-3-phosphate dehydrogenase promoter. The recombinant enzyme was optimally active at 55°C and pH 4.5 with Km and Vmax values of 1.0 mM and 250 μmol min−1 mg−1 respectively against 4-nitrophenyl β-xylopyranoside. Xylose was a competitive inhibitor with a Ki of 2.72 mM, whereas fructose was an uncompetitive inhibitor reducing substrate binding affinity (Km) and conversion efficiency (Vmax). The enzyme was characterised to be an exo-cutting enzyme releasing xylose from the non-reducing ends of β-1,4 linked xylooligosaccharides (X2, X3 and X4). Catalytic conversion of X2, X3 and X4 decreased (Vmax and kcat) with increasing chain length.
Highlights
Xylanolytic and cellulolytic enzymes encoded by filamentous fungi have been employed in several industrial applications for improving digestibility in animal feed, production of sweeteners, pharmaceuticals, additive chemicals for biofuel production and for the replacement of hazardous chemicals in textile and paper manufacture (Michelin et al 2012)
As a consequence it has been a necessity for enzymes involved in cellulose and hemicellulose hydrolysis to be individually identified and characterised in order to utilise them in the process of converting waste agricultural materials into valuable products with greater efficiency
Characterisation of recombinant β-xylosidase The β-xylosidase gene is contained within an open reading frame of 2397 nucleotides with no introns, which encodes a protein of 798 amino acids
Summary
Xylanolytic and cellulolytic enzymes encoded by filamentous fungi have been employed in several industrial applications for improving digestibility in animal feed, production of sweeteners, pharmaceuticals, additive chemicals for biofuel production and for the replacement of hazardous chemicals in textile and paper manufacture (Michelin et al 2012). As a consequence it has been a necessity for enzymes involved in cellulose and hemicellulose hydrolysis to be individually identified and characterised in order to utilise them in the process of converting waste agricultural materials into valuable products with greater efficiency. Of a β-xylosidase from Aspergillus oryzae in Pichia pastoris and the kinetic characterisation of the recombinant enzyme
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
