A new approach for proteases production by Aspergillus niger based on the kinetic and thermodynamic parameters of the enzymes obtained

This study reports the proteases production by Aspergillus niger LBA02 under solid state fermentation using different agroindustrial wastes and the variation of the biochemical properties of these proteases in response to each substrate. The biochemical properties of the proteases varied widely when produced in wheat bran (PWB), soybean meal (PSM), cottonseed meal (PCM), orange peel (POP) and the quaternary mixture of them (PQM). The lower value for activation energy (Ea) was detected for protease POP (16.32 kJ mol−1) and the higher for protease PQM (19.48 kJ mol−1). The temperature quotient (Q10) values ranging from 1.20 to 1.28 at temperatures between 35.0 and 55.0 °C. The higher Vmax/Km ratio was 562.79 U mL g−1 mg−1 for the protease PSM. The order of thermal stability of the proteases at temperatures ranging from 40 to 60 °C as revealed from t1/2 and D values and thermodynamic parameters Ead (activation energy for irreversible deactivation), ΔH (enthalpy), ΔG (Gibbs free energy) and ΔS (entropy) was: PWB>PQM>POP>PSM>PCM. In the study of the substrate specificity, the best substrate was hemoglobin from bovine blood. Our study provides a new point of view for proteases production under solid state fermentation, which was possible to evaluate the most suitable substrate for secretion of enzymes with more attractive characteristics based on their biochemical properties, such as high thermal stability.