Abstract: Considering that currently glucose oxidase (GOD), a food-grade enzyme, is industrially produced in low yield, in this study, we chose the glucose oxidase gene goxC from Aspergillus niger CBS513.88 for modification by codon optimization and signal peptide replacement to construct a recombinant strain with high GOD activity. Aconidial A. niger strain SH2, low-background ofsecreted proteins, was used as the host, carrying the high efficient promoter PglaA. Positive transformants were selected using the auxotroph marker pyrG. Catalytic assay of o-dianisidine and SDS-PAGE results showed that the recombinant glucose oxidase with a molecular mass of 80 kDa was successfully expressed in A. niger SH2. The enzymatic activity reached 563.8 U/mL on the 7th day of fermentation in a 500-mL shake flask. In the 50-L tank fermentation, the enzymatic activity attained 1 128 U/mL at 179 h, which was over twice as much as that achieved in the shaking flask fermentation. In the current study, the expression of glucose oxidase was higher than previous literature values in A. niger expression system. This study showed that the optimum temperature and pH of the recombinant glucose oxidase were 45 ℃ and 5.5, respectively. Overall, a recombinant A. niger strain highly effective expression of goxC has been constructed.

Key words: glucose oxidase, Aspergillus niger, high-level expression, enzymatic characteristics