Immobilization of β-glucosidase from Aspergillus niger on κ-carrageenan hybrid matrix and its application on the production of reducing sugar from macroalgae cellulosic residue

• Novel glutaraldehyde activated κC-PEI polyelectrolyte complex beads were prepared.
• β-glucosidase immobilized on hybrid matrix beads retained high activity.
• The immobilized β-glucosidase showed enhanced activity and good reusability.

A novel concept for the synthesis of a stable polymer hybrid matrix bead was developed in this study. The beads were further applied for enzyme immobilization to produce stable and active biocatalysts with low enzyme leakage, and high immobilization efficiency, enzyme activity, and recyclability. The immobilization conditions, including PEI concentration, activation time and pH of the PEI solution were investigated and optimized. All formulated beads were characterized for its functionalized groups, composition, surface morphology and thermal stability. Compared with the free β-glucosidase, the immobilized β-glucosidase on the hybrid matrix bead was able to tolerate broader range of pH values and higher reaction temperature up to 60 °C. The immobilized β-glucosidase was then used to hydrolyse pretreated macroalgae cellulosic residue (MCR) for the production of reducing sugar and a hydrolysis yield of 73.4% was obtained. After repeated twelve runs, immobilized β-glucosidase retained about 75% of its initial activity.