Production, biochemical characterization, and kinetic/thermodynamic study of novel serine protease from Aspergillus avenaceus URM 6706.

This work aimed the characterization of protease produced by Aspergillus avenaceus URM 6706 from the Caatinga/Brazil. The optimization of production by central composite design increased the protease activity 15.47 times. The protease had a pH optimum of 7.0 and a temperature optimum of 50°C. The enzyme activity was kept at 96.7 and 80% at a pH 7.0 and 40°C, respectively for 180 min. No metal ion has altered a protease activity considerably. The sodium dodecyl sulfate (SDS) inhibited protease activity by 50%. The protease was inhibited by PMSF, so the enzyme is serine protease. The Km , Vmax , and kcat values were of 0.358 mg/ml, 16.31 mg·ml-1 ·min-1 , and 1.58 s-1 , respectively. The activation energy for the hydrolysis of azocasein catalyzed by protease also estimated (E* = 14.4 kJ/mol). Evaluating the protease thermal denaturation was observed that higher half-life values (277.2≤t1/2 ≤912.2 min) indicating a good thermostability confirmed by the results of thermodynamic parameters the activation energy for thermal inactivation (E*d = 100.3 kJ/mol), enthalpy (97.43≤ΔH*d≤97.64 kJ/mol), and Gibbs free energy (104.13≤ΔG*d≤104.77 kJ/mol). The results obtained suggest that this protease produced by A. avenaceus URM 6706, which proved to be thermostable and, could be profitably exploited in industrial applications.