Abstract

This study aims topurification and characterization of theglucoamylase enzyme from Aspergillus niger, the enzyme was purified by ammonium sulfate precipitation (80%) , dialysis and gel filtration chromatography using sephadex G- 200, A trial for the purification of glucoamylase using gel filtration technique resulted in two types of glucoamylase (A& B) with specific activity of (4.195 , 21.466) respectively and terminal specific activity of glucoamylase (B) was reached (31.214 U/mg) with (10.689 folds) purification . the purified glucoamylase (A&B) had a maximum activity at pH = 8, 6.5, 40,30 °C respectively , the glucoamylase (B) was stable with pH values ranging between (6 6.5) and the enzyme was maintained the activity when it incubated into (10 -35) °C for 30 minutes while keep 65% of its activity in temperature 40 °C also glucoamylase (B) was stable in 30°C for ( 10-30 ) minutes , analyses of the glucoamylase (A&B) for molecular weight was carried out by PAGE and SDS-PAGE electrophoresis, which revealed 52 and 66 KDa respectively , also molecular weight of the glucoamylase (B) was achieved by gel filtration technique and was found 68 KDa this means that enzyme consisting of only one subunit , the Km and Vmax value of glucoamylase (B) were (2.8 mM, 9.8 mM/min ) respectively using different concentration of starch