Statistical optimization of enzyme cocktail production using Jew's mallow stalks residues by a new isolate Aspergillus flavus B2 via statistical strategy and enzymes characterization.

Abstract

This study investigates the production of the enzyme cocktail by the isolated fungi Aspergillus flavus B2 (GenBank accession number OL655454) using agricultural and industrial (AI) residues as the sole substrate. Of all the AI residues tested, Jew's mallow stalk was the best inducer substrate for enzyme cocktail production without adding any nutrients. Statistical optimization using Response Surface Methodology enhanced the production by 5.45, 5.20, and 3.34-fold, respectively for pectinase, xylanase, and CMCase. Optimum temperature, activation energy (Ea), and activation energy for denaturation (Ed) were determined. Michaelis constant (Km) for CMCase, xylanase, and pectinase enzyme was 1.82, 1.23, and 1.05mg/mL, respectively. Maximum reaction rate (Vmax) was 4.67, 5.29, and 17.13U/mL, respectively for CMCase, xylanase, and pectinase. Thermal stability revealed that pectinase, CMCase, and xylanase enzymes retained 64.7%, 61.8%, and 53.2% residual activities after incubation for 1h at 50°C. Half-life time (t0.5) of pectinase, CMCase, and xylanase at 50°C were 189.38, 129.8, and 127.89min, respectively. Thermodynamics of the produced enzymes enthalpy (ΔH*d), free energy (ΔG*d), and entropy (ΔS*d) were determined at 40, 50, and 60°C. In the presence of EDTA (5mM), CMCase, xylanase, and pectinase retained 69.5%, 66.2%, and 41.2%, respectively of their activity. This work is significant for the valorization of AI residues and the production of value-added products.