Continuous Bioconversion of Oleuropein from Olive Leaf Extract to Produce the Bioactive Product Hydroxytyrosol Using Carrier-Immobilized Enzyme

Abstract

Feasibility and stability were evaluated of a continuous multi-batch process for converting oleuropein (OLE) from olive leaf extract to the bioactive product hydroxytyrosol (HT). Carrier beads made of three different materials (calcium alginate, chitosan with deacetylated α-chitin nanofibers (DEChN), or porous ceramic) were investigated for morphology, thermogravimetric, sorption, and viscoelastic properties. Enzymatic hydrolysis of OLE conducted in a packed bed bioreactor containing cellulase immobilized to carrier beads yielded OLE degradation rates of ~ 90% and an average HT yield of ~ 70% over 20 batches. Ultimately, inorganic porous ceramic beads were less costly and exhibited superior performance relative to organic carriers and thus were deemed most suitable for industrial-scale HT production. Systems utilizing enzyme immobilization within packed bed reactors hold promise for achieving efficient production of valuable bioproducts from discarded biomass materials.