Pectinex Ultra SP-L was immobilized on magnetic duolite-polystyrene particles. Immobilization and reaction conditions were determined by a viscometric method in the batch system reactor. Maximum free and immobilized activities of the enzyme were both obtained at 65 degreesC and pH 6. Activation energies for free and immobilized enzymes were calculated as 4.39 and 6.83 kcal mole(-1) respectively. The kinetics of free and Duolite A568-immobilized pectinase was investigated. Michaelis-Menten constants and maximal reaction rates were found as K-m = 0.515 g ml(-1) and V-max = 1.047 x 10(-3) g mul(-1) s(-1) for free enzyme and K-m = 1.877 g ml(-1) and V-max = 5.569 x 10(-3) g s(-1) g particles(-1) for immobilized pectinase at 20 degreesC. (C) 2003 Elsevier Ltd. All rights reserved.