Efficient immobilization of a fungal laccase and its exploitation in fruit juice clarification

Abstract

The clarification step represents, in fruit juices industries, a bottleneck process because residual phenols cause severe haze formation affecting juice quality and impairing customers acceptance. An enzymatic step can be efficiently integrated in the process, and use of immobilized enzymes entails an economical advantage. In this work, covalent immobilization of recombinant POXA1b laccase from Pleurotus ostreatus on epoxy activated poly(methacrylate) beads was optimized thanks to a Response Surface Methodologies approach. Through regression analysis the process was well fitted by a quadratic polynomial equation (R(2)=0.9367, adjusted R(2)=0.8226) under which laccase activity reached 2000 ± 100 Ug(-1) of beads, with an immobilization efficiency of 98%. The immobilized biocatalyst was characterized and then tested in fruit juice clarification reaching up to 45% phenol reduction, without affecting health-effective flavanones content. Furthermore, laccase treated juice displays an improved sensory profile, due to the reduction of vinyl guaiacol, a potent off-flavor possessing a peppery/spicy aroma.

Keywords: Food industry; Laccase immobilization; Mass spectrometry analysis; Phenols; Response Surface Methodology.