Preparation and properties of immobilized pummelo limonoid glucosyltransferase

In order to explore the possibility of using in a bioreactor for debittering citrus juice, pummelo limonoid glucosyltransferase (LGTase) was ionically and covalently immobilized on different carriers and the properties of the immobilized enzyme were investigated. The enzyme immobilized ionically on DEAE-Toyopearl (DE-Tp-LGTase) and covalently on chitosan cross-linked with gluteraldehyde (Chito-GA-LGTase) and on cellulose carbonate (Ce-Ca-LGTase) had high LGTase activity. Optimum pH shifted from 7.8 for free LGTase to 8.2 for DE-Tp-LGTase and to 7.4 for Chito-GA-LGTase, but remained unchanged for Ce-Ca-LGTase. K-m values for limonin of immobilized LGTase were higher than that of free LGTase. The optimum temperature was unaffected by immobilization, while thermal stability improved appreciably in case of Cc-Ca-LGTase. The immobilized LGTase retained more than 80% activity up to 15 cycles on cellulose carbonate, nine cycles on chitosan and six cycles on DEAE-Toyopearl. (C) 2002 Elsevier Science Ltd. All rights reserved.