Production, thermodynamic characterization, and fruit juice quality improvement characteristics of an Exo-polygalacturonase from Penicillium janczewskii

Exo-polygalacturonase (Exo-PG), an extracellular pectinolytic Enzyme with great potential in the food industry, was produced from Penicillium janczewskii under solid-state fermentation using wheat bran as a lignocellulosic substrate. Optimization of various fermentation process variables revealed that a moisture level of 70%, d-mannitol (carbon source), yeast extract (nitrogen source) and ZnSO₄/NiCl₂ as metal salt inducers generated the maximum yield of Exo-PG. After ammonium sulfate precipitation (70% saturation level), the Enzyme was characterized in terms of various kinetic (i.e., temperature, pH, inhibitors, Michaelis-Menten constants) and thermodynamic parameters (i.e., Ea, ΔH*, ΔS* and ΔG*). The temperature and pH optima were 45 °C and 6.0, respectively, and the Exo-PG presented stability at a wider range of temperature and pH values. Metal ions Mn⁺² markedly improved the Enzyme activity, while exposure to urea and ethylenediaminetetraacetic acid drastically inhibited the biocatalytic performance. The kinetic parameters i.e., k_m and V_max were computed to be 10 mM and 41.67 U/mL, respectively. A profound increase in clarity, yield, and reduction in viscosity was achieved for different fruit juices (apple, mango, and peach) after treatment with Exo-PG. Total antioxidant and total phenolic contents were also ameliorated. In conclusion, the catalytic activity, thermal steadiness, and fruit juices clarification performance of Exo-PG manifests a great prospect for bio-industrial exploitation.

Antioxidants; Exo-polygalacturonase; Fruit juice clarification; Kinetic; Penicillium janczewskii; Solid-state fermentation; Thermodynamic parameters.