title: Improvement of activity, thermo-stability and fruit juice clarification characteristics of fungal exo-polygalacturonase.
abstract: An extracellular exo-polygalacturonase (exo-PG) from Penicillium notatum was immobilized in sodium-alginate matrix through two different protocols, viz. covalent bonding and adsorption to enhance its catalytic activity, thermal stability and life-time properties for industrial applications. Covalent immobilization was more efficient in terms of high relative activity (45.89%) and immobilization yield (71.6%) as compared to adsorption. Immobilized exo-PG derivatives displayed maximum activities at pH 5.5 and 55°C as compared to free enzyme which showed its optimum activity at pH 6.0 and 50°C. The affinity of enzyme towards its substrate (Km(app)) was reduced after immobilization and Vmaxof covalently immobilized exo-PG decreased to 66.7% while the Vmaxvalue of adsorbed enzyme increased up to 150% as compared to free counterpart. Both immobilization techniques greatly enhanced the thermal stability profile of the enzyme. At 60°C, immobilized exo-PGs retained more than 90% of their residual activities after 60min of heating, while free enzyme did not show any activity at the same temperature. Thermodynamic properties (i.e., Ea, ΔH*, ΔS*and ΔG*) of the free and immobilized enzymes were also investigated. Sodium-alginate covalently immobilized and adsorbed enzymes showed excellent recycling efficiencies and retained 50.0% and 41.0% of original activities, respectively after seven consecutive batch reactions. Moreover, the immobilized enzymes treatment achieved promising results in turbidity and viscosity reduction as well as clarity amelioration in various fruit juices. Altogether catalytic, thermo-stability and fruit juices clarification characteristics of the immobilized ex-PGs suggest a high potential for biotechnological exploitability.
authors.affiliation: Environmental & Material Chemistry Laboratory, Department of Chemistry, University of Agriculture, Faisalabad 38040, Pakistan; Department of Chemistry, Government College Women University, Faisalabad, Pakistan.
authors.forename: Faiza
authors.initials: F
authors.lastname: Amin
authors.affiliation: Environmental & Material Chemistry Laboratory, Department of Chemistry, University of Agriculture, Faisalabad 38040, Pakistan.
authors.forename: Haq Nawaz
authors.initials: HN
authors.lastname: Bhatti
authors.affiliation: Industrial Biotechnology Laboratory, Department of Biochemistry, University of Agriculture, Faisalabad 38040, Pakistan. Electronic address: bilaluaf@hotmail.com.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Bilal
authors.affiliation: Industrial Biotechnology Laboratory, Department of Biochemistry, University of Agriculture, Faisalabad 38040, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Asgher
mesh_terms: D000327:Adsorption; D000464:Alginates / Q000737:chemistry; D055162:Biocatalysis; D004789:Enzyme Activation; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D019649:Food Industry; D000067030:Fruit and Vegetable Juices; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010408:Penicillium chrysogenum / Q000201:enzymology*; D011096:Polygalacturonase / Q000737:chemistry* / Q000378:metabolism*; D013696:Temperature
chemical_list: D000464:Alginates; D004800:Enzymes, Immobilized; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D011096:Polygalacturonase
keywords: Adsorption; Covalent immobilization; Exo-polygalacturonase; Juice clarification; Recycling efficiency; Thermo-stability; Thermodynamics