Optimization of Polyphenol Oxidase Immobilization in Copper Alginate Beads

Abstract

Polyphenol oxidase (PPO, EC 1.14.18.1) was isolated from artichoke head (Cynara scolymus L.) by using 0.1 M Tris-HCl buffer (pH 7.0), concentrated by (NH₄)₂SO₄ precipitation, and immobilized in copper-alginate beads. Immobilization yield was determined to be 70%. The cresolase and catecholase activities of enzyme immobilized at optimum immobilization conditions were found to be 13.3 and 670 U g beads min⁻¹, respectively. Effects of immobilization conditions such as alginate concentration, CaCl₂ concentration, amount of loading enzyme, bead size, and amount of beads on enzymatic activity were investigated. Optimum alginate and CuCl₂ concentration were found to be 2 % and 3 % (w/v), respectively. Using bead (diameter 3 mm) amount of 0.25 g maximum enzyme activities were observed for both polyphenol activities. The initial concentrations of loading free enzyme were 6.5U mL⁻¹ and 5815 U mL⁻¹ for cresolase activity and catecholase activities, respectively. Beads prepared at optimum immobilization conditions were suitable for up to 8 repeated uses.

Keywords::

• polyphenol oxidase
• artichoke
• alginate
• entrapment
• cresolase activity
• catecholase activity

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.