Abstract
Mesoporous silica materials offer a unique opportunity for enzyme immobilization thanks to their properties, such as tuneable pore size, large surface area and easy functionalization. However, a significant enhancement of cellulase enzyme activity entrapped inside the silica pores still represents a challenge. In this work, we immobilized cellulase by adsorption on wrinkled silica nanoparticles (WSNs), obtaining an active and stable biocatalyst. We used pentanol as co-solvent to synthesize WSNs with enhanced inter-wrinkle distance in order to improve cellulase hosting. The physical-chemical and morphological characterization of WSNs and cellulase/WSNs was performed by thermogravimetric (TG), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) analyses. The obtained results showed that this matrix generates a favourable microenvironment for hosting cellulase. The results of the catalytic assays and operational stability confirmed the key role of size, morphology and distribution of the pores in the successful outcome of the cellulase immobilization process. The immobilization procedure used allowed preserving most of the secondary structure of the enzyme and, consequently, its catalytic activity. Moreover, the same value of glucose yield was observed for five consecutive runs, showing a high operational stability of the biocatalyst.
Highlights
Over the last Century, the scientific community have devolved a huge interest to address the problems of fossil fuel depletion and climate change [1]
The physical-chemical and morphological characterization of wrinkled silica nanoparticles (WSNs) and cellulase/WSNs was performed by thermogravimetric (TG), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) analyses
The results of the catalytic assays and operational stability confirmed the key role of size, morphology and distribution of the pores in the successful outcome of the cellulase immobilization process
Summary
Mesoporous silica can be used for many applications such as drug delivery, fluorescence biological probes [6,7] and are suitable supports for enzyme immobilization [8,9,10] They have high chemical, mechanical and thermal stability. WSNs have wrinkles that widens radially outward enhancing the accessibility of functional materials inside the pores and reducing pore blocking They were used for lipase [27] and β-glucosidase [28,29,30] immobilization. The immobilised β-glucosidase showed better catalytic performance than free enzyme and high thermal and operational stability This was attributed to the peculiar morphology of the pores and their hierarchical structure allowing for optimal hosting of β-glucosidase and avoiding diffusion problems of the substrate [28,29]. The aim was to increase the loading and activity of cellulase on mesoporous silica nanoparticles without the need to functionalize the support with organic compounds
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