In this work, sequential optimization strategy, based on statistical designs, was employed to enhance the production of α-amylase by Aspergillus niger ATCC 16404. This statistical study consists of optimizing the factors that influence the production of α-amylase of A. niger ATCC 16404. Indeed, another statistical study has allowed the selection of 5 factors (pH, starch, yeast extract, "corn steep liquor", CaCl2 and salts) affecting both the development of mould (biomass) and that of the enzyme production. The central composite design allows the determination of the optimum of these selected factors and a quadratic model explains the factor reaction. Thus, the "ridge analysis" method, has led to maximizing the experimental reaction. The results indicate that the production rate of α-amylase is maximized in the presence of starch at 8.97 g/l, yeast extract at 2.86 g/l, CaCl2 at 1.224 g/l, salts (composed of 25% FeSO4, 7H2O, 25% MnSO4 and 50% MgCl2, 6H2O): FeSO4, 7H2O, MnSO4 0.1518 g/l and MgCl2, 6H2O at 0.3036 g/l. As for the pH, it is maintained at the rate of 5.68.
α-Amylase, Aspergillus niger, Optimization, Central Composite Design, Ridge Regression.