Entrapment of enzyme aggregates in chitosan beads for aroma release in white wines

Glycosidases are enzymes involved in the cascade reactions leading to the release of aromatic compounds in white wines. However, the use of commercial soluble glycosidases is facing difficulties due to their fast inactivation, poor reaction control, low efficiency of enzyme use, and the presence of catalyst residues in the product. Co-immobilization as cross-linked enzyme aggregates (combi-CLEAs) is a sound alternative allowing the immobilization of enzymes in their own protein matrix, yielding highly stable and active biocatalysts. Notwithstanding, their micrometer sized particles limit their application in industrial processes. To overcome this, combi-CLEAs of β-D-glucosidase (βG) and α-L-arabinofuranosidase (ARA) were entrapped in polymeric chitosan beads. The effect of crosslinking reagents and crosslinking time on the specific activity and stability of combi-CLEAs was studied, and the best conditions for the entrapment of the combi-CLEAs in polymeric chitosan beads were determined varying the concentration of the chitosan solution and the pH of the gelation agent solution. The resulting biocatalyst beads (average diameter 1.24 mm), retained full activity after 91 days of incubation under winemaking conditions, having specific activities of 0.91 and 0.88 international units of activity per gram for βG and ARA, respectively. Such characteristics make them suitable for aroma enhancement in wines.