Chitosan beads from microbial and animal sources as enzyme supports for wine application

Chitosan beads from a microbial source, i.e. Aspergillus niger (An), were produced by precipitation method for the first time and compared with supports prepared from an animal source, i.e. shellfish derived chitosan with three different molecular weights (low (LMW), medium (MMW) and high (HMW)). The produced beads were used as enzyme carriers to be applied in a continuous packed-bed reactor (PBR) for white wine protein stabilization. For this purpose, the beads were crosslinked with glutaraldehyde (GDH) and stem bromelain was immobilized on the carrier surface as a model enzyme, following two different procedures (i.e., cross-linking with glutaraldehyde (GDH) and direct linkage (DL)). Drop-like beads with an average diameter of 3.0-3.5 mm and a moisture content of 86-94% were obtained. The morphology of the produced beads in dried state, in terms of shape and surface, was studied by means of a scanning electron microscope (SEM), evidencing the obtainment of nearly spherical or oval particles. The efficacy of the crosslinking procedure and of bromelain immobilization was demonstrated by means of SEM investigation and infrared spectroscopy (FT-IR) analysis, revealing a rougher surface. Various initial protein concentrations ranging between 0.45 and 18.00 mg(BSAeq) mL(-1) were tested in order to identify the optimal amount and to evaluate the influence of the initial concentration on the total protein loading. Stem bromelain proved to be more active when immobilized by DL on An beads and was efficient in reducing white wine hazing potential continuously, as verified with a laboratory bench-scale PBR. (C) 2016 Elsevier Ltd. All rights reserved.