An organofunctionalized MgO∙SiO2 hybrid support and its performance in the immobilization of lipase from Candida rugosa

Adsorption-precipitation-cross-linking immobilization of GDSL-type esterase from Aspergillus niger GZUF36 by polydopamine-modified magnetic clarity tetroxide nanocouplings and its enzymatic characterization

Recombinant INANE1 (rINANE1), a recombinant intracellular GDSL-type esterase from Aspergillus niger GZUF36, has high acetate substrate specificity. Here, rINANE1 was successfully immobilized on polydopamine (PDA)-modified magnetic ferric oxide nanoparticles (Fe₃O₄NPs) by adsorption-precipitation-cross-linking to obtain cross-linked enzyme aggregate (CLEA)-rINANE1-Fe₃O₄@PDA. Fe₃O₄, Fe₃O₄@PDA, and CLEA-rINANE1-Fe₃O₄@PDA were characterized by scanning electron microscopy, X-ray diffraction, vibrating-sample magnetometry, Fourier transform infrared (FTIR) spectroscopy, and zeta potential analysis. Upon immobilization, CLEA-rINANE1-Fe₃O₄@PDA, with a protein loading of 72.72 ± 1.01 mg/g, reached optimal activity recovery of 104.40 % ± 1.14 %. FTIR analysis showed that immobilization increased the relative content of β-folding in rINANE1 by 12.25 % and reduced irregular curl by 4.16 %, rendering the structure more orderly. Specifically, under an alkaline condition (pH 10), CLEA-rINANE1-Fe₃O₄@PDA performed over 100 % of initial activity. The optimum temperature increased by 5 °C, and over 55 % of the initial activity was observed after 12 h at 55 °C. CLEA-rINANE1-Fe₃O₄@PDA showed over 40 % of its relative activity, whereas free rINANE1 showed <10 % in acetonitrile. In addition, the relative activity of CLEA-rINANE1-Fe₃O₄@PDA was retained at about 80 % after eight cycles and maintained at 109 % after 45 days. The PDA-modified magnetic ferrite nanoparticles exhibited excellent stability and recyclability, providing a new avenue for developing industrial biocatalysts.

SILP materials based on TiO2-SiO2 and TiO2-SiO2/lignin supports as new catalytic materials for hydrosilylation reaction - synthesis, physicochemical characterization and catalysis

The oxide system TiO2-SiO2 as well as a TiO2-SiO2/lignin system have been obtained by the sol-gel synthesis method and applied as supports in Supported Ionic Liquid Phase (SILP) materials. In total 24 SILP systems were obtained with ionic liquids containing imidazolium, pyridinium, phosphonium or sulfonic cations and bis(trifluoromethylsulfonyl)imide or methylsulfate anions, and homogeneous complexes of rhodium or platinum as the active phase. The supports and catalytic materials were subjected to thorough characterization by elemental analysis, XRD, SEM-EDX, IR, and TGA, and their particle size distribution and porous properties were assessed. The new SILP materials were used in hydrosilylation of 1-octene with 1,1,1,3,5,5,5-heptamethyltrisiloxane. The effectiveness of hydrosilylation reaction catalyzed by the obtained SILP materials for the polar and nonpolar reagents was assessed. All the catalytically active materials were proved to be easy to isolate and reuse, and the best SILP systems have been shown to be active in 10 or more subsequent catalytic cycles.

Functionalized Silicas for Metal-Free and Metal-Based Catalytic Applications: A Review in Perspective of Green Chemistry

Heterogeneous catalysis plays a key role in promoting green chemistry through many routes. The functionalizable reactive silanols highlight silica as a beguiling support for the preparation of heterogeneous catalysts. Metal active sites anchored on functionalized silica (FS) usually demonstrate the better dispersion and stability due to their firm chemical interaction with FSs. Having certain functional groups in structure, FSs can act as the useful catalysts for few organic reactions even without the need of metal active sites which are termed as the covetous reusable organocatalysts. Magnetic FSs have laid the platform where the effortless recovery of catalysts is realized just using an external magnet, resulting in the simplified reaction procedure. Using FSs of multiple functional groups, we can envisage the shortened reaction pathway and, reduced chemical uses and chemical wastes. Unstable bio-molecules like enzymes have been stabilized when they get chemically anchored on FSs. The resultant solid bio-catalysts exhibited very good reusability in many catalytic reactions. Getting provoked from the green chemistry aspects and benefits of FS-based catalysts, we confer the recent literature and progress focusing on the significance of FSs in heterogeneous catalysis. This review covers the preparative methods, types and catalytic applications of FSs. A special emphasis is given to the metal-free FS catalysts, multiple FS-based catalysts and magnetic FSs. Through this review, we presume that the contribution of FSs to green chemistry can be well understood. The future perspective of FSs and the improvements still required for implementing FS-based catalysts in practical applications have been narrated at the end of this review.