Development of an efficient production method for β‐mannosidase by the creation of an overexpression system in Aspergillus aculeatus

Aim:  To develop an overexpression system in Aspergillus aculeatus in order to establish an efficient overproduction method of β‐mannosidase (MANB). Methods and Results:  An overexpression plasmid for the manB gene, encoding A. aculeatus MANB, was constructed and introduced into A. aculeatus cells. The gene was overexpressed under an improved promoter containing 12 copies of Region III cis ‐elements of Aspergillus oryzae in the transformant, and it secreted 2·56 mg MANB ml −1 in liquid culture, which obtained a 9·4‐fold higher productivity than that achieved in an overexpression system in A. oryzae . Most of the secreted protein in the cultured medium of the transformed A. aculeatus was the overproduced enzyme. Conclusions:  Aspergillus aculeatus with the introduced overexpression plasmid produced 2·56 mg MANB ml −1 in cultured medium. The improved promoter with A. oryzae Region III functioned in A. aculeatus ; thus the strain is an expectant host for recombinant protein productions. Significance and Impact of the Study:  The overexpression system with the improved promoter in A. aculeatus brought the highest productivity of MANB reported to date. The expression system would be a strong bioindustrial tool for protein production.