Enzymatic Characterization of Glucoamylase from Aspergillus niger Mutant

Mutant strain of Aspergillus niger by electron beam was selected to be the object. To explore the enzymatic characteristics of glucoamylase produced by mutant strain of Aspergillus niger by the optimum pH test,the optimum temperature test,thermal stability test,acid-base stability test and the expetiment on the offect of metal ions on the activity of glucoamyase. The results showed that glucoamylase was produce at 63℃and the highest enzyme activity was 26% higher than the original strain. 8.4 kU/mL enzyme activity was remained when the glucoamylase produced by the mutant strain was inactivated at 80℃,the themal stability of the glucoamylase produced by the mutant strain is obviously improved. The optimum pH of glucoamylase from Aspergillus niger Mutant was 4.6,and the highest enzyme activity was 24%,which higher than that of the glucoamylase from original strain. When the glucoamylase produced by the original strain was inactivated,there were still 6.9 kU/mL enzyme activity remained,the pH stability of the glucoamylast was produced by the mutant strain was obviously improved. Its activity was increased by K⁺,Mg²⁺,Ca²⁺ to a certain extent,and inhibited by Ag⁺,Fe²⁺,Cu²⁺ to varying degrees,had little and or no significant effect by Zn²⁺,EDTA.