Abstract
SUMMARYResearch backgroundPectinase enzyme has become a valuable compound in beverage industry. One of the most significant concepts to overcome the drawbacks of using industrial enzymes is their immobilization. In the present study, magnetic chitosan microparticles were utilized as a substrate for pectinase immobilization. New methods of enzyme immobilization involve the use of non-chemical cross-linkers between the enzyme and the substrate. The aim of this study is to immobilize the pectinase enzyme using polyaldehyde kefiran as a macromolecular cross-linker on magnetic particles.Experimental approachPectinase was immobilized in four steps: relative oxidation of kefiran and its application as a cross-linker, production of magnetic iron(II) iron(III) oxide (Fe3O4) microparticles, coating of magnetic Fe3O4 microparticles with chitosan, and immobilization of the enzyme on the substrate, prepared by the use of oxidized kefiran cross-linker. Parameters such as cross-linking concentration, time and ratio of chitosan magnetic microparticles to enzyme were optimized. Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering, transmission electron microscopy, and vibrating sample magnetometer were used to identify the groups and investigate the structures. The biochemical properties (stability of enzyme activity at different pH, temperature and time), enzyme reusability, kinetic parameters (Km and νmax) and apple juice turbidity, using free and immobilized pectinase enzymes, were also measured.Results and conclusionsCross-linker concentration, cross-linking time and the ratio of magnetic Fe3O4 microparticles with chitosan to enzyme were important factors in activity recovery of pectinase. FTIR analysis correctly identified functional groups in the structures. The results showed that after enzyme stabilization, the particle size and molecular mass, respectively, increased and decreased the magnetic saturation strength. According to the thermal kinetic study, the activity of the immobilized pectinase was higher than of its free form. The findings of this study indicate excellent stability and durability of the immobilized pectinase. Finally, a magnetic pectinase micro-biocatalyst was used to clarify apple juice, which reduced turbidity during processing.Novelty and scientific contributionThis study investigates the usage of kefiran oxidized as a new cross-linker for the immobilization of pectinase enzyme. Magnetic pectinase micro-biocatalyst has a good potential for industrial applications in the food industry, with high thermal stability.
Highlights
In recent years, juice production technologies have attracted major attention in order to improve their quality due to the increased consumption of natural juices
The findings of this study indicate excellent stability and durability of the immobilized pectinase
This study investigates the usage of kefiran oxidized as a new cross-linker for the immobilization of pectinase enzyme
Summary
Juice production technologies have attracted major attention in order to improve their quality due to the increased consumption of natural juices. Juices with added pectinase have a clearer appearance and filterability than enzyme-depleted counterparts [1]. Squeezed juice has a turbid appearance due to the colloidal dispersion of pectin (1.5 to 0.9 %) in the cell wall structure, which is one of the most important disadvantages of fruit juice processing [2]. Pectic substances are a complex of glycoside macromolecules with a high molecular mass. These substances can be found in plants and are responsible for the structure and integrity of plant tissue [3]. KHODAIYAN: Magnetic Biocatalysts for Clarification of Apple Juice
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