A hyperstable polypeptide with cellulolytic and xylanolytic activity

Abstract

The present invention relates to a polynucleotide encodes polypeptide (CbCel) shows cellulolytic activity with specific activity of 165.7 U mg-1 at 70°C and pH 6.0, using p-nitrophenyl-βcellobioside (pNPC), and the truncated version of this polynucleotide encodes a polypeptide (CbXyl) has optimal xylanolytic activity towards birchwood xylan with 254 U mg-1 specific activity at 70°C and pH 6.0. The invention further relates to nucleic acid constructs, vectors, and engineered bacterial cells comprising the polynucleotide, as well as methods of producing polypeptides. The genetically modified bacterial cells express cellobiohydrolase and xylanase individually. Both polypeptides are thermal and pH stable, and quite stable at 55°C for 7 h in a range of pH 5.5-8.0. Additionally, both are resistant to various chemical inhibitors (metal ions, detergents, and organic solvents), and have long hydrolysis times and reusability. The invention also discloses the applications of polypeptides, methods for degrading lignocellulosic biomass using CbCel and CbXyl polypeptides discretely, and producing bio-products, preferably bioethanol, using 100 U at 55°C and pH 5.0-8.0 after 2 h. Moreover, this invention finds utility in the textile, leather softening, food, and paper and pulp industries.