Bacillus subtilis lipase (BSL2) has been successfully immobilized into a Cu-BTC based hierarchically porous metal-organic framework material for the first time. The Cu-BTC hierarchically porous MOF material with large mesopore apertures is prepared conveniently by using a template-free strategy under mild conditions. The immobilized BSL2 presents high enzymatic activity and perfect reusability during the esterification reaction. After 10 cycles, the immobilized BSL2 still exhibits 90.7% of its initial enzymatic activity and 99.6% of its initial conversion.
Functional molecules synthesized by self-assembly between inorganic salts and amino acids have attracted much attention in recent years. A simple method is reported here for fabricating hybrid organic-inorganic nanoflowers using copper (II) ions as the inorganic component and natural amino acids as the organic component. The results indicate that the interactions between amino acid and copper ions cause the growth of the nanoflowers composed by C, N, Cu, P and O elements. The Cu ions and Cu(AA) n complexes containing Cu-O bond are present in the nanoflowers. The nanoflowers have flower-like porous structure dominated by the R groups of amino acids with high surface-to-volume ratios, which is beneficial for exerting its peroxidase-like activity depending on Fenton-like reaction mechanism with ABTS and Rhodamine B as the substrates. It is expected that the nanoflowers hold great promise as enzyme mimics for application in the field of biosensor, bioanalysis and biocatalysis.Numerous works have been devoted to the synthesis and characterization of the nano-structured materials [1][2][3][4][5][6] . These studies are paving the way from the nano-to macro-scopic world. Among of the nano-structured materials, the bio-inspired materials with micro-and nano-scale have been proposed as a big breakthrough on the design of advanced functional materials and have attracted much attention in recent years due to the huge advantage of the bio-molecules in directing and assembling the superstructures 7 . For example, Zare and co-workers have successfully prepared protein-inorganic hybrid nanostructures with flower-like shapes in 2012 8 . When an enzyme is used as the protein component, the hybrid nanoflower exhibits enhanced enzymatic activity and stability compared with the free enzyme. This is attributed to the high surface area and confinement of the enzymes in the nanoflowers. The peptide nanoparticles have also been prepared via different routes and exhibit excellent function as catalyst or as a basis of smart and responsive materials that can sense or control diverse biological events 9 . However, it still remains a big challenge for scientists to assemble bioinorganic hybrid structures into the complex hierarchical architectures for their wide potential applications 10 . Amino acids are considered as the major building blocks of all naturally occurring peptides and proteins. Furthermore, their side chains vary a lot from each other, making them have the potential usefulness in chiral molecular recognition and selection processes 11,12 . Here, we describe a simple method for fabricating the hybrid organic-inorganic nanoflowers using copper (II) ions as the inorganic component and natural amino acids as the organic component under the mild conditions.
Results and DiscussionIn a typical experiment, the hybrid organic-inorganic nanoflowers were prepared by mixing 20 μL of aqueous CuSO 4 solution (120 mM) and 3 mL of phosphate buffer (pH 7.4) containing asparagine (Asn) (60 μg) at 25 °C. After 24 hours, a blue precipitate with ...
Acting as a “green” manufacturing route, the enzyme toolbox made up of galactose oxidase, catalase, and horseradish peroxidase can achieve a satisfactory yield of 2,5-diformylfuran derived from 30 mM hydroxymethylfurfural. However, as the concentration of hydroxymethylfurfural increases, the substrate causes oxidative damage to the activity of the tri-enzyme system, and the accumulated hydrogen peroxide produced by galactose oxidase causes tri-enzyme inactivation. The cost of tri-enzymes is also very high. These problems prevent the utilization of this enzyme toolbox in practice. To address this, galactose oxidase, catalase, and horseradish peroxidase were co-immobilized into Cu3(PO4)2 nanoflowers in this study. The resulting co-immobilized tri-enzymes possessed better tolerance towards the oxidative damage caused by hydroxymethylfurfural at high concentrations, as compared to free tri-enzymes. Moreover, the 2,5-diformylfuran yield of co-immobilized tri-enzymes (95.7 ± 2.7%) was 1.06 times higher than that of separately immobilized enzymes (90.4 ± 1.9%). This result could be attributed to the boosted protective effect provided by catalase to the activity of galactose oxidase, owing to the physical proximity between them on the same support. After 30 recycles, co-immobilized tri-enzymes still achieves 86% of the initial yield. Moreover, co-immobilized tri-enzymes show enhanced thermal stability compared with free tri-enzymes. This work paves the way for the production of 2,5-diformylfuran from hydroxymethylfurfural via co-immobilized tri-enzymes.
The enzymatic performance of trypsin in hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA) was improved by adsorption on Santa Barbara Amorphous (SBA)-15 mesoporous silica. The optimal immobilization conditions were screened and the properties of immobilized enzyme have also been studied. Under the optimal conditions, the immobilized trypsin displays maximum specific activity (49.8 μmol/min/g). The results also indicate that the immobilized trypsin exhibits better storage stability.
Abstract:The laccase-incorporated nanoflower was fabricated and characterized by scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM images indicate that the laccase-incorporated nanoflower has a high surface area, which may facilitate the mass transfer of the substrate and the product. FTIR spectrums identify the existence of laccase in the nanoflowers. The novel immobilized laccase was used for the synthesis of viniferin. The reaction conditions had been optimized and the laccase-incorporated nanoflower can show its maximum specific activity (16.3 µmol/g/h) under the optimal reaction conditions. The specific activity of the laccase in the nanoflowers is enhanced about 2.2-fold compared with free laccase in solution without copper (II) ions. Furthermore, the laccase in the nanoflowers shows an increase in specific activity of~180% compared with free laccase in a solution containing high concentrations (similar to the concentration in the flower) of copper (II) ions. The results also indicate that the laccase in the nanoflowers retain 93.2% of its initial specific activity even after ten continuous batches.
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