Kinetic and thermodynamic insight of a polygalacturonase: A biocatalyst for industrial fruit juice clarification

Abstract

In this study, complete purification, characterization, and immobilization of polygalacturonase (pectinase) from Penicillium notatum were carried out to achieve an economical and suitable alternative for industrial fruit juice clarification. Biosynthesis of polygalacturonase was carried out under pre-optimized conditions employing solid-state fermentation at a pilot scale using wheat bran. The enzyme was subjected to a series of steps for purification including ion-exchange chromatography. After that, the purified enzyme was characterized and its kinetics and thermodynamic parameters along with the effect of immobilization on its performance were studied. Finally, a purified acidic enzyme was tested for its clarifying abilities on fresh apple juice. Purification fold of 2.98 was attained with increased specific activity of 256U/mg. Purified polygalacturonase showed a molecular weight of 38 kDa, optimum temperature of 50°C, optimum pH of 5, 50% stability at 50°C, and 84% stability at pH 5. The “Vmax” and “Km” of the enzyme were evaluated to be 250U/mg and 0.11mg/mL, respectively for hydrolyzing pectin. From the Arrhenius plot, activation energy (Ea), enthalpy of activation (ΔH), and entropy of activation (ΔS) were found to be 6.35 KJ/mol, 3.67 KJ/mol, and -1.1KJ/mol, respectively. Among metal ions, most of the tested Organic solvents and inhibitors inhibited the activity. Nano emulsion-based pectinase exhibited better stability. The enzyme was found to be an effective agent for the clarification of fresh apple juice.