Screening and identification of exo-1,4-β-D-glucannase-producing fungi, and its expression in Pichia pastoris

Abstract:

[Objective] Exoglucanases is a class of cellulase which could degradation crystalline cellulose. Nowadays, how to improve the exoglucanase activity is of importance. [Methods] In this study, strain ASP-524, possessing higher level of cellobiohydrolase, was identified as Aspergillus niger. The cbhB gene was cloned from strain ASP-524, and expressed in Pichia pastoris GS115. [Results] After the induction of 1% methanol for 5 d, the expression strain reached a cellulase activity of 4.74 U/mL. The recombinant exoglucanase was a 57 kD protein with an optimum catalytic activity at pH 5.0 and 50 °C. [Conclusion] The enzyme was stable. The recombinant exoglucanase was relatively stable in a broad pH range, from 4.0 to 6.0, and retained 80% activity.

Key words:Aspergillus niger Asp-524, Exoglucanase, Pichia pastoris, Strain identification