Abstract: Glucoamylase from Gliocladium roseum was secretively expressed in Aspergillus niger G1 strain. A putative glucoamylase gene(about 1. 8 kb)was amplified by PCR using genomic DNA of G. roseum as template. The amplified products were ligated into the clone vector pGm to construct recombinant plasmid pGm-3440. The recombinant plasmid transformed into A. niger G1 strain, and amdS screening and PCR validation confirmed that an engineering Aspergillus strain of expressing glucoamylase was obtained. Fermentation of recombinant strain indicated that secretive expression of the glucoamylase gene was available in A. niger, and its enzyme activity was measured by method defined in national standard(QB/T 1803-1993), and it reached 292 U/mL. Further enzymatic analysis demonstrated that the optimum pH and temperature for the recombinant enzyme were 5. 0 and 50℃, respectively. Meanwhile, it had poor thermal resistance, but promising pH stability.

Key words: glucoamylase, Gliocladium roseum, Aspergillus niger G1, secretive expression