Optimization of Glucoamylase Production by Local Isolate of Aspergillus niger Using Agro-Industrial Substrates under Solid State Fermentation

In this work, a local isolate of Aspergillus niger was used in the production of glucoamylaseunder Solid state fermentation (SSF).When A. niger grown on different agro-industrial wastes, wheat bran was the most promising fermentable substrate for glucoamylase production. Maximum activity of glucoamylase was recorded when the level moisture content was 1.5:1 (v/w) of wheat bran: distilled water. All additive carbon sources decreased the production of the enzyme, while, among organic and inorganic nitrogen sources, addition of 1% (w/w) calcium nitrate gave the best results of the production of the enzyme. The optimum inoculum size, temperature and pH  for enzyme production was 1.5ml, 30ºC and 5.5, respectively.The highest activity of the produced enzyme was recorded at 70ºC and pH 5.5. Also, metal salts affected the activity of the enzyme. CuSO₄ gave maximum activity, while HgCl₂ made a huge decrease in the activity. The enzyme showed a great stability at 50ºC and a moderate stability at 60ºC. Also, the enzyme exhibited great stability at acidic condition of incubation.