Abstract

• Isolation and purification of pectinase enzyme from the peels of white dragon fruit (Selenicereus undatus) were performed by 20-80 % ammonium sulphate precipitation followed by gel filtration chromatography on Sephadex G-100. Pectinase enzyme activity was determined using glucose as a standard and pectin as a substrate by a UV-Vis spectrophotometer at 591 nm. The optimum pH and temperature of crude and partially purified pectinase enzymes extracted from the white dragon fruit peels were found as 5 and 30 ͦ C, respectively. The activation energies (Ea) of the crude and purified pectinase-catalyzed reactions were observed as 4.1185 kcal mol-1 and 3.4018 kcal mol-1, respectively. The Km and Vmax values were found as 0.300 × 10-2 g mL-1 and 25.380 × 10-2 mM min-1 for crude pectinase enzyme and 0.509 × 10-2 g mL-1 and 26.281 × 10-2 mM min-1 for partially purified pectinase enzyme, using the Lineweaver-Burk plot. The reaction order (n) of the crude and purified pectinase-catalyzed reactions was calculated using the linear regression method, and it was found to be first order. Both crude and partially purified pectinase enzymes were used in the clarification of grape juice and the transmittance percents were 75.49 % and 86.29 %, respectively. The clarity of grape juice can be improved by enzymatic treatment using pectinase.