Improvement of the glaB promoter expressed in solid-state fermentation (SSF) of Aspergillus oryzae

The glucoamylase-encoding gene (glaB) promoter should be very useful for recombinant protein production in solid-state fermentation (SSF) of Aspergillus oryzae. A 97-bp fragment containing the cis-element of the glaB promoter was inserted into the glaA promoter, which was little expressed in SSF. The chimeric promoter showed about a 24-fold increase in promoter activity in SSF. Eight copies of the 97-bp fragment were tandemly fused with the glaB promoter. The improved promoter showed about a 4.6-fold increase in promoter activity in SSF. The glaB gene was overexpressed under control of the improved glaB promoter in SSF. Recombinant glucoamylase production reached about 1524 mg/kg-broth for 2 d. The improved glaB promoter should be very useful for overproduction of a recombinant protein in SSF of A. oryzae.