Pectinase Immobilization on Porous Polyamide Microparticles: Characterization, Operational Stability and Application in Wine Clarification
Abstract
Lyophilized pectinase from Aspergillus niger (PeL) was immobilized onto polyamide 6 (PA6) microparticles (MPs) through an adsorption-based procedure within the pH range of 5–8, yielding four PeL@PA6 complexes. In contrast to commercial enological preparations that are complex enzymatic cocktails with unspecified exact compositions, the use of PeL with known specific activity enabled a more reliable evaluation and improvement of the immobilization process and of the structure–activity relationships of the resulting biocatalysts. Thermogravimetric analysis demonstrated better thermal stability of the PeL@PA6 complexes compared to neat PA6 MPs. UV-CD studies revealed that the secondary structure and conformational stability of PeL before and after immobilization were strongly pH-dependent, with maximum stability observed at pH 6–7. All four PeL@PA6 complexes retained significant catalytic activity and showed good tolerance to ethanol-rich media relevant to enological applications. Kinetic analysis indicated increased apparent Km values after immobilization, suggesting diffusional limitations associated with the porous PA6 support. Clarification experiments of industrial white and rosé wine musts confirmed the practical applicability of the immobilized system. All PeL@PA6 complexes preserved the color and phenolic integrity of the musts, displayed good operational stability during reuse, and exhibited higher long-term storage stability than the free enzyme. These results demonstrate that PA6 MPs are promising supports for pectinase immobilization in wine clarification and related biotechnological applications.