Despite the extensive efforts of scientific community towards the development of a vast variety of immobilization methods, there is a limited number of immobilized biocatalysts used at industrial scale. Most often, cost issues prevent the transfer of methodologies to large scale but more recently also sustainability criteria are becoming increasingly relevant, so that petroleum based carriers for enzyme immobilization appear unsuitable for responding to new challenges of green and renewable chemistry. Here we report, for the first time, a preliminary overview of the potential of rice husk as carrier to be employed for both physical and covalent immobilization of enzymes. The data indicate that the chemical versatility of this lignocellulosic biomass, containing also silica, opens wide scenarios for optimizing different immobilization procedures requiring minimal pre-treatments and applicable to various enzymes and process conditions. The mechanical and chemical robustness of rice husk, along with its virtual unlimited availability worldwide, make this inexpensive natural matrix a promising candidate for replacing organic fossil-based carriers for enzyme immobilization.Computational construction of 3D models and surface analysis. Protein structures were visualized and recorded using the PyMOL software. The 3D-structures used for the hydrophobicity comparisons were retrieved from the PDB with the codes 1TCA for CaLB, 5DPF for Thermolysin and 4EQV for Invertase

The high cost and environmental impact of fossil-based organic carriers represent a critical bottleneck to their use in large-scale industrial processes. The present study demonstrates the applicability of rice husk as inexpensive renewable carrier for the immobilization of enzymes applicable sectors where the covalent anchorage of the protein is a pre-requisite for preventing protein contamination while assuring the recyclability. Rice husk was oxidized and then functionalized with a di-amino spacer. The morphological characterization shed light on the properties that affect the functionalization processes. Lipase B from Candida antarctica (CaLB) and two commercial asparaginases were immobilized covalently achieving higher immobilization yield than previously reported. All enzymes were immobilized also on commercial epoxy methacrylic resins and the CaLB immobilized on rice husk demonstrated a higher efficiency in the solvent-free polycondensation of dimethylitaconate. CaLB on rice husk appears particularly suitable for applications in highly viscous processes because of the unusual combination of its low density and remarkable mechanical robustness. In the case of the two asparaginases, the biocatalyst immobilized on rice husk performed in aqueous solution at least as efficiently as the enzyme immobilized on methacrylic resins, although the rice husk loaded a lower amount of protein.