A Submerged Production of Glucoamylase from Selected Agro-Waste by Using Aspergillus niger

Production of glucoamylase (GA) by using various agro-wastes as carbon sources has been widely carried out as an environmentally friendly approach with a competent value-added result. Similar to other value-added products generated by a bioconversion process, the characteristics of produced enzymes highly depend on the selected medium and microbial strain. Oilseeds such as canola, safflower, soybean, and sunflower are among those agricultural products in the country with a rising rate of production. Therefore, optimal use of their meals will lead to economic and environmental profitability. Thus, in the present study, dry potato peel and waste, soybean, canola, sunflower and safflower meals were evaluated as the basic carbon sources. Aspergillus Niger van Tieghem IBRC-M 30064 was used throughout the study as the selected microbial strain. A set of experimental runs was designed to assess the effect of different variables on GA production and activity. Eventually, the crude GA without further purification was characterized in terms of enzyme activity, quantitative protein, optimal pH, temperature, and thermo-stability. The highest GA activity (~33 IU/mL) was obtained under the following conditions: the concentration of cornstarch (100 g/L), the concentration of safflower meal (50 g/L), at 32.5 °C, for 123 h, 120 rpm of shaking rate, with 48 h and 5% (v/v) of inoculum age and size, respectively. The produced enzyme acquired a high-purity with 150 IU/mg of specific activity. By this new approach, the use of safflower meal waste (50 g/L) with (100 g/L), can produce glucoamylase with high activity and favorable characteristics.