Abstractl-asparaginase (ASNase, EC 3.5.1.1) is an enzyme that catalyzes the l-asparagine hydrolysis into l-aspartic acid and ammonia, being mainly applied in pharmaceutical and food industries. However, some disadvantages are associated with its free form, such as the ASNase short half-life, which may be overcome by enzyme immobilization. In this work, the immobilization of ASNase by adsorption over pristine and modified multi-walled carbon nanotubes (MWCNTs) was investigated, the latter corresponding to functionalized MWCNTs through a hydrothermal oxidation treatment. Different operating conditions, including pH, contact time and ASNase/MWCNT mass ratio, as well as the operational stability of the immobilized ASNase, were evaluated. For comparison purposes, data regarding the ASNase immobilization with pristine MWCNT was detailed. The characterization of the ASNase-MWCNT bioconjugate was addressed using different techniques, namely Transmission Electron Microscopy (TEM), Thermogravimetric Analysis (TGA) and Raman spectroscopy. Functionalized MWCNTs showed promising results, with an immobilization yield and a relative recovered activity of commercial ASNase above 95% under the optimized adsorption conditions (pH 8, 60 min of contact and 1.5 × 10–3 g mL−1 of ASNase). The ASNase-MWCNT bioconjugate also showed improved enzyme operational stability (6 consecutive reaction cycles without activity loss), paving the way for its use in industrial processes.
Nanoparticles (NPs) of titanium dioxide (TiO2) are promising for the photocatalytic degradation of organic compounds, arising as an excellent alternative to conventional bleaching processes. Within this background, aqueous suspensions of TiO2 NPs were impregnated by the pad-dry method in raw cotton. The hydrophilic properties and whiteness index (WI) of Berger were the main parameters examined before and after the TiO2 treatment. In the absence of water, using a UV-Vis lamp, high hydrophilicity was found for raw cotton. Diversely, under UV-LED radiation, the presence of water molecules in the coated cotton was revealed to be a crucial parameter in enhancing its whiteness. A comparable WI of Berger with conventional bleaching methods was obtained using 0.5 g L-1 TiO2 suspension under UV-LED radiation, suggesting that the impregnation of TiO2 NPs can be a promising alternative for the industrial bleaching methods, as it proves to be more sustainable and with low operating costs.
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