Stabilization by multipoint covalent attachment of a biocatalyst with polygalacturonase activity used for juice clarification

• A novel immobilized PG active biocatalyst was developed for juice clarification.
• Immobilized biocatalyst in glyoxyl-agarose showed high yield and stability.
• Protein loading on biocatalyst was optimized by sequential immobilization process.
• 18 successive reactions (90 h) were carried out with acceptable enzymatic activity.
• Grape (10.6 °Bx) and plum (4.7 °Bx) juices were clarified with immobilized PG.

Derivatized-agarose supports are suitable for enzyme immobilization by different methods, taking advantage of different physical, chemical and biological conditions of the protein and the support. In this study, agarose particles were modified with MANAE, PEI and glyoxyl groups and evaluated to stabilize polygalacturonase from Streptomyces halstedii ATCC 10897. A new immobilized biocatalyst was developed using glyoxyl-agarose as support; it exhibited high performance in degrading polygalacturonic acid and releasing oligogalacturonides. Maximal enzyme activity was detected at 5 h of reaction using 0.05 g/mL of immobilized biocatalyst, which released 3 mg/mL of reducing sugars and allowed the highest product yield conversion and increased stability. These results are very favorable for pectin degradation with reusability up to 18 successive reactions (90 h) and application in juice clarification. Plum (4.7 °Bx) and grape (10.6 °Bx) juices were successfully clarified, increasing reducing sugars content and markedly decreasing turbidity and viscosity.