Periodate-driven mesopore evolution in dialdehyde cellulose beads for horseradish peroxidase immobilization and...

Enzyme immobilization can improve catalyst stability and reusability, but the relationship between support structure and enzyme performance is often not well defined. Here, cellulose beads (CBs) were oxidized with sodium periodate for different times to alter their mesoporous structure and introduce aldehyde groups for horseradish peroxidase (HRP) immobilization. The resulting dialdehyde cellulose beads (DACBs) were characterized using SEM-EDS, FT-IR, XRD, XPS, and N₂ adsorption-desorption measurements. As oxidation time increased, the mean pore size first increased from 13.76 to 14.59 nm and then decreased to 9.45 nm. DACBs oxidized for 3 h provided the most favorable balance between HRP immobilization and preservation of accessible mesopores, yielding HRP-DACBs with an activity of 2.85 U g^-1 wet support that retained 71.9% of their initial activity after 10 catalytic cycles. The immobilized enzyme achieved >83% apparent TC removal over a concentration range of 10-100 mg L^-1 at a fixed H₂O₂/TC molar ratio of 6. LC-MS analysis suggested transformation pathways involving hydroxylation, demethylation, dehydration, decarbonylation, and ring-cleavage-related reactions. DFT calculations indicated high electronic susceptibility to oxidation in the conjugated keto/enol and adjacent hydroxyl/carbonyl regions of TC. Together, these results show that periodate oxidation can tune the pore structure and aldehyde content of the resulting DACBs for HRP immobilization, and that the resulting HRP-DACBs can be reused for TC transformation.