Cloning of a Gene Encoding Xylanase B from Aspergillus niger and its Expression in Escherichia coli

摘要

In this study, the gene xynB encoding xylanase B, obtained from Aspergillus niger AN-1 was cloned and efficiently expresed in E. coli BL21. The full-length gene contained 658 bp and encoded a mature protein containing 225 amino acids. The purified, recombinant xylanase XYNB showed one band at about 25 kDa. The maximum yeild of the recombinant xylamase was 4.09x105 U g-1 which was higher than that obtained when Aspergillus niger was solid state fermented. The optimal temperature of XYNB was 50°C and recombinant enzyme displayed about 75% of peak activity in the temperature range found in the body of animals to which the enzyme might be fed. The optimum pH of XYNB was about pH 5.0 and the recombinant enzyme retained >80% enzyme activity in the pH range found in the animal gastrointestinal tract where the enzyme might take effect. These enzyme properties suggested that this enzyme could be potentially useful in feed industry.