Immobilization of Commercial Pectinase (Polygalacturonase) on Celite and Its Application in Juice Clarification

Abstract

The commercial pectinase (polygalacturonase) was immobilized on celite through adsorption. There was 2.5% concentration of glutaraldehyde used as cross-linking agent and a binding time of 4 h was found to be the best time for its proper binding. Binding efficiency of enzyme to the matrix was 43.18%. The immobilized enzyme retained almost 50% of activity after third cycle of reuse. Free enzyme showed maximum activity with polygalacturonic acid (PGA, 0.9%) as substrate at 40C temperature, pH 5.5 and incubation time of 20 min while immobilized enzyme showed maximum activity with PGA (0.9%) as substrate at temperature of 45C, pH 5.5 and incubation time of 15 min. Both free and immobilized enzyme were inhibited by metal ions, thiols, phenolics and protein inhibitors. For clarification of 1.0 mL of pineapple juice, 20 mg of immobilized enzyme per mL of juice at 45C temperature and 1 h of holding time was optimized. Practical Applications Pectinases find commercial application in fruit juice, wine, oil, tea, coffee, textile and paper-making industries using a wide variety of carriers and methods. One of the vital applications is the clarification and depectinization of fruit juices. The raw fruit juice obtained after pressing is very turbid viscous and contains a significant amount of colloidal compounds, mainly pectin that causes cloudiness; therefore, clarification of fruit juices involves the removal of juice haze by enzyme hydrolysis with pectolytic enzymes. Although pectinases enhance the clarification of juices, immobilization of these enzymes proves to be beneficial for industrial use. Immobilization of pectinase on celite through adsorption is a simple, cheap and effective method. For the clarification of pineapple juice, excellent results were observed using immobilized polygalacturonase in comparison with free enzyme.