Glass with high visible-light transparency is widely considered as the most important optical material, which typically requires a processing temperature higher than 1000 °C. Here, we report a translucent aluminosilicate glass that can be prepared by cold sintering process (CSP) at merely 300 °C. After eliminating structural pores in hexagonal faujasite (EMT)-type zeolite by heat treatment, the obtained highly active nanoparticles are consolidated to have nearly full density by adding NaOH solution as liquid aids. However, direct densification of EMT powder cannot remove the structural pores of zeolite completely, leading to an opaque compact after the CSP. It is proved that the chemical reaction between the NaOH- and zeolite-derived powders is highly beneficial to dissolution-precipitation process during sintering, leading to the ultra-low activation energy of 27.13 kJ/mol. Although the addition of 5 M NaOH solution greatly promotes the densification via the reaction with aluminosilicate powder, lower or higher concentration of solvent can deteriorate the transmittance of glass. Additionally, the CSP-prepared glass exhibits a Vickers hardness of 4.3 GPa, reaching 60% of the reported value for spark plasma sintering (SPS)-prepared sample.
Novel composite nanoparticles were prepared from lysozyme and modified poly (γ-glutamic acid) to be used as emulsifiers for Pickering emulsions. Increasing the pH value of the solution facilitated the formation of gel-like emulsions suitable for releasing lysozyme.
Self‐stable precipitation polymerization was used to prepare an enzyme‐immobilized microsphere composite. Phosphomannose isomerase (PMI) with His‐tag was successfully immobilized on Ni2+ charged pyridine‐derived particles. The maximum amount of PMI immobilized on such particles was ∼184 mg/g. Compared with free enzyme, the activity of the immobilized enzymes was significantly improved. In addition, the immobilized enzymes showed a much better thermostability than free enzymes. At the same time, the immobilized enzymes can be reused for multiple reaction cycles. We observed that the enzyme activity did not decrease significantly after six cycles. We conclude that the pyridine‐derived particles can be used to selectively immobilize His‐tagged enzymes, which can couple the enzyme purification and catalysis steps and improve the efficiency of enzyme‐catalyzed industrial processes.
Ion exchange resins are suitable as carriers for immobilized enzymes because of their stable physicochemical properties, appropriate particle size and pore structure, and lower loss in continuous operation. In this paper, we report the application of the Ni-chelated ion exchange resin in the immobilization of His-tagged enzyme and protein purification. Acrylic weak acid cation exchange resin (D113H) was selected from four cationic macroporous resins that could chelate the transition metal ion Ni. The maximum adsorption capacity of Ni was ~198 mg/g. Phosphomannose isomerase (PMI) can be successfully immobilized on Ni-chelated D113H from crude enzyme solution through chelation of transition metal ions with the His-tag on the enzyme. The maximum amount of immobilized PMI on the resin was ~143 mg/g. Notably, the immobilized enzyme showed excellent reusability and maintained 92% of its initial activity with 10 cycles of catalytic reaction. In addition, PMI was successfully purified using an affinity chromatography column prepared by Ni-chelated D113H, which showed the potential for the immobilization and purification process to be realized in one step.
As a natural macromolecular material, starch is an ideal carrier for enzyme immobilization because of its widely available source, easy regeneration and excellent biodegradability. However, the natural starch cannot be directly used for immobilization due to the large particle size and excessive hydrophilicity. In this paper, the epoxy groups were grafted onto esterified starch by bifunctional reagents. The grafting efficiency of epoxy groups was increased by starvation drop addition. The changes of contact angle and particle size are conducive to the adsorption of immobilized enzyme at the water oil interface in the subsequent enzyme catalytic reaction, hence improve of the lipase activity. The maximum amount of lipase mobilized on such modified starch was ∼143.7 mg/g, which was near 40 mg/g higher than that of those from direct crosslinking. The immobilized enzymes showed excellent resistance to organic solvents and good reusability. Immobilization of lipases on epoxy‐functionalized starch nanoparticles can potentially improves the possibility of enzymes industrial application.
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