Cloning of a cellobiohydrolase gene (cbhl) from Aspergillus niger and heterogenous expression in Pichia pastoris

摘要

A gene encoding a cellobiohydrolase (CBH) was isolated from Aspergillus niger-NL-1 and designated as cbhl. The cbhl gene contains 1,515 nucleotides with three introns and encodes a 452-amino acid protein with a molecular weight of approximately 60 kDa. The amino acid sequence encoded by cbh1 shows high homology with the sequence of glycoside hydrolase fimily 7. The cellobiohydrolase (cbhl) gene was successfully expressed in Pichia pastoris KM71H. The recombinant CBHIshowed an optimal working condition at 60°C, pH 4.0 with K_m and V_(max) toward CMC-Na of 13.81 mM and 0.269 μmol/min, respectively. The enzyme retained more than 80% of its initial activity after 2 h of incubation at 90°C and was stable in pH range 1.0～10.0. Because of its moderately stable at high temperature and stability through wide range of pH, this enzyme has potential in various industrial applications.