The Possibility of Recovering of Hydroxytyrosol from Olive Milling Wastewater by Enzymatic Bioconversion

Abstract

This chapter discusses an innovative approach to obtain liquid fractions from olive mill wastewater (OMW) rich in hydroxytyrosol. The method is based on bioconversion combined with membrane separation techniques. An enzymatic bioconversion of three types of OMW was tested. TheS total volumes of OMW are 15 and 40 L. The reaction was monitored in mechanically stirred systems for 2 h at 50°C. Maximum hydroxytyr-osol concentrations of about 1.53, 0.83 and 0.46 g/L in the presence of 5 IU Aspergillus niger β-glucosidase per milliliter from North OMW and South OMW were procured by two different olive millings, which are milling super press (MSP) and milling continuous chain (MCC), respectively. Enzymatic pretreatment was followed by two tangential flow membrane separation stages, microfiltration (MF) and ultrafiltration (UF). The ultrafiltration permeate was concentrated by evaporation at 45°C for 2 h. The latter exhibited a chemical oxygen demand (COD) level of 48.44 g/L. The UF permeate dehydration increased the hydroxytyrosol concentration to 7.2 g/L. A new natural product that contains some minerals beneficial to health and devoid of heavy metals or chemicals was obtained by this innovative work which describes an environmentally friendly process at pilot-scale.