Stabilized Cellulase in Chitosan–Polyvinyl Alcohol Biopolymer Beads for Sustainable Enzymatic Deinking of Recycled Paper

Developing stable and reusable biocatalysts is crucial for improving the sustainability of industrial processes, including enzymatic deinking. In this article, cellulase is immobilized onto chitosan-polyvinyl alcohol (Cs/PVA/Ga) biopolymer beads using glutaraldehyde cross-linking, creating a durable and recyclable catalytic system. Scanning electron microscopy revealed a bead-like structure, and fourier transform infrared spectroscopy spectra confirmed successful enzyme incorporation without compromising the polymer's integrity. Immobilization shifted the optimal activity of cellulase from pH 5 to pH 8 and raised the temperature optimum from 50 °C to between 60 and 70 °C, indicating improved catalytic stability. Kinetic studies showed a decrease in Km from 0.75 mM for the free enzyme to 0.4mM for the immobilized form, suggesting increased substrate affinity. Thermal stability tests revealed cellulase@Cs/PVA/Ga maintained over 83% of its activity at 80 °C for 60 min, compared to only 50% for the free enzyme. The immobilized cellulase demonstrated 90% activity retention after seven reuse cycles. Biodeinking experiments with recycled pulp evidenced optimal cellulose and hemicellulose retention with a 5% enzyme dosage, while effluent analysis showed enhanced removal of ink residues with the immobilized enzyme, highlighting the ecoefficient potential of this approach for sustainable paper recycling.