17 research outputs found
Improved Stabilities of Immobilized Glucoamylase on Functionalized Mesoporous Silica Synthesised using Decane as Swelling Agent
Ordered mesoporous silica, with high porosity was used to immobilize glucoamylase via adsorption and covalent binding. Immobilization of glucoamylase within mesoporous silica was successfully achieved, resulting in catalytically high efficiency during starch hydrolysis. In this study, mesoporous silica was functionalized by co-condensation of tetraethoxysilane (TEOS) with organosilane (3-aminopropyl) triethoxysilane (APTES) in a wide range of molar ratios of APTES: TEOS in the presence of triblock copolymer P123 under acidic hydrothermal conditions. The prepared materials were characterized by Small angle XRD, Nitrogen adsorption – desorption and 29Si MAS solid state NMR. N2 desorption studies showed that pore size distribution decreases due to pore blockage after functionalization and enzyme immobilization. Small angle XRD and 29Si MAS NMR study reveals mesophase formation and Si environment of the materials. The main aim of our work was to study the catalytical activity, effect of pH, temperature storage stability and reusability of covalently bound glucoamylase on mesoporous silica support. The result shows that the stability of enzyme can be enhanced by immobilization. © 2013 BCREC UNDIP. All rights reservedReceived: 3rd December 2012; Revised: 4th April 2013; Accepted: 20th April 2013[How to Cite: George, R., Gopinath, S., Sugunan, S. (2013). Improved Stabilities of Immobilized Glucoamyl-ase on Functionalized Mesoporous Silica Synthesized using Decane as Swelling Agent. Bulletin of Chemical Reaction Engineering & Catalysis, 8 (1): 70-76. (doi:10.9767/bcrec.8.1.4208.70-76)][Permalink/DOI: http://dx.doi.org/10.9767/bcrec.8.1.4208.70-76] | View in | </p
Tuning mesoporous molecular sieve SBA-15 for the immobilization of α-amylase
The present work describes the immobilization of α-amylase over well ordered mesoporous molecular sieve SBA-15 with different pore diameters synthesized by post synthesis treatment (PST) hydrothermally after reaction at 40°C. The materials were characterized by N 2 adsorption–desorption studies, small angle X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. Since α-amylase obtained from Bacillus subtilis has dimensions of 35 × 40 × 70 Å it is expected that the protein have access to the pore of SBA-15 (PST-120°C) with diameter 74 Å. The pore dimension is appropriate to prevent considerable leaching. The rate of adsorption of the enzyme on silica of various pore sizes revealed the influence of morphology, pore diameter, pore volume and pH.Cochin University of Science
and Technolog
Catalytic oxidation of cyclohexane over Cu-Zn-Cr ternary spinel systems
Spinel systems with the composition of Cu 1−x Zn x Cr 2 O 4 [x = 0 CCr, x = 0.25 CZCr-1, x = 0.5 CZCr-2, x = 0.75 CZCr-3 and x = 1 ZCr] were prepared by homogeneous co-precipitation method and were characterized by X-ray diffraction (XRD) and FT-IR spectroscopy. Elemental analysis was done by EDX, and surface area measurements by the BET method. The redox behavior of these catalysts in cyclohexane oxidation at 243 K using TBHP as oxidant was examined. Cyclohexanone was the major product over all catalysts with some cyclohexanol. 69.2% selectivity to cyclohexanol and cyclohexanone at 23% conversion of cyclohexane was realized over zinc chromite spinels in 10 h.Cochin University of Science and Technolog
Glucoamylase immobilized on montmorillonite: influence of nature of binding on surface properties of clay-support and activity of enzyme
Glucoamylase was immobilized on acid
activated montmorillonite clay via two different procedures
namely adsorption and covalent binding. The
immobilized enzymes were characterized by XRD,
NMR and N2 adsorption measurements and the
activity of immobilized glucoamylase for starch
hydrolysis was determined in a batch reactor. XRD
shows intercalation of enzyme into the clay matrix
during both immobilization procedures. Intercalation
occurs via the side chains of the amino acid residues,
the entire polypeptide backbone being situated at the
periphery of the clay matrix. 27Al NMR studies
revealed the different nature of interaction of enzyme
with the support for both immobilization techniques.
N2 adsorption measurements indicated a sharp drop in
surface area and pore volume for the covalently bound
glucoamylase that suggested severe pore blockage.
Activity studies were performed in a batch reactor. The
adsorbed and covalently bound glucoamylase retained
49% and 66% activity of the free enzyme respectively.
They showed enhanced pH and thermal stabilities. The
immobilized enzymes also followed Michaelis–Menten
kinetics. Km was greater than the free enzyme that was
attributed to an effect of immobilization. The immobilized
preparations demonstrated increased reusability
as well as storage stability.Cochin University of
Science & Technolog
Synthesis of polyaniline-montmorillonite nanocomposites using H2O2 as the oxidant
Polyaniline montmorillonite nanocomposite was prepared using H2O2 as the oxidant. The catalytic environment of montmorillonite favours polymerization. Intercalation and composite formation was proven from various techniques such as XRD, FTIR, DRS and thermal analysis. XRD patterns give the dimension of the intercalated PANI, from the shift of 2θ values, which is in the nano range. FTIR showed that PANI composite formation occured without affecting the basic clay layer structure. Thus the successful development of an alternative cheap route for polyaniline–montmorillonite nanocomposite was well established
Effect of rare earth metal ions on the structural and textural properties of NaFAU-Y zeolite and vapour phase alkylation of benzene with 1-octene
676-688Rare earth
exchanged (La3+, Ce3+, RE3+, Sm3+)
Na-Y zeolites were prepared by simple ion exchange methods. X-ray diffraction
pattern and IR spectral studies show that the frameworks remain intact after
exchange with rare earth metal ions. The surface acidic properties were
determined by temperature programmed desorption of ammonia (NH3-TPD).
1H MAS-NMR spectral study shows the presence of highly acidic
bridging hydroxy groups in the zeolite structure. Considerable enhancement in
the acid structural properties is observed on rare earth exchange. Strain
induced by the bulky rare earth metal cations on the zeolitic framework has
been followed by a perceptible shift in the positions of 29Si and 27Al
MAS-NMR spectral peaks. The migration of counter cations, especially lanthanum,
in the repulsive electrostatic field of sodium has been established using 29Si
and 27Al MAS-NMR studies. The catalytic efficiency of the prepared
systems was tested for the alkylation of benzene with 1-octene. Zeolite Na-Y
shows very low activity due the negative influence of Na+ ions on
the Brönsted acid centres. Rare earth exchanged forms invariably show
better selectivity for the desired 2-phenyloctane formation. Catalysts are
susceptible for deactivation due to blocking of the pores by alkylation
products. These studies show that the rare earth exchanged zeolites exhibit
better resistance towards deactivation
Alkylation of Benzene with I-Octene over Titania Pillared Monmorillonite
Linear alkylbenzene sulfonic acid, the largest-volume synthetic surfactant, in addition to its excellent performance , is important due to its biodegradable environmental friendliness, as it has a straight chain and is prepared by the sulphonation of linear alkylbenzenes (LAB). To ensure environmental protection, the commercial benzene alkylation catalysts HF or AICI3 are replaced and we have developed a clean LAB production process using a pillared clay catalyst capable of not only replacing the conventional homogeneous catalyst, but also having high selectivity for the best biodegradable 2-phenyl LAB isomer .Pillared clay catalysts having high Bronsted acidity show efficient conversion in gas phase alkylation of benzene with 1-octene with a good 2-phenyl octane selectivity
Solid acid-catalyzed dehydration/Beckmann rearrangement of aldoximes: towards high atom efficiency green processes
Rare earth metal ion exchanged (La3+, Ce3+, RE3+) KFAU-Y zeolites were prepared by simple ion-exchange methods and have
been characterized using different physico-chemical techniques. In this paper a novel application of solid acid catalysts in the dehydration/
Beckmann rearrangement of aldoximes; benzaldoxime and 4-methoxybenzaldoxime is reported. Dehydration/Beckmann
rearrangement reactions of benzaldoxime and 4-methoxybenzaldoxime is carried out in a continuous down flow reactor at
473K. 4-Methoxybenzaldoxime gave both Beckmann rearrangement product (4-methoxyphenylformamide) and dehydration product
(4-methoxybenzonitrile) in high overall yields. The difference in behavior of the aldoximes is explained in terms of electronic
effects. The production of benzonitrile was near quantitative under heterogeneous reaction conditions. The optimal protocol allows
nitriles to be synthesized in good yields through the dehydration of aldoximes. Time on stream studies show a fast decline in the
activity of the catalyst due to neutralization of acid sites by the basic reactant and product molecules.Cochin University of Science and Technolog
Synthesis of dimethyl acetal of ketones: design of solid acid catalysts for one-pot acetalization reaction
The synthesis of dimethyl acetals of carbonyl compounds such as cyclohexanone, acetophenone, and benzophenone has successfully been carried out by the reaction between ketones and methanol using different solid acid catalysts. The strong influence of the textural properties of the catalysts such as acid amount and adsorption properties (surface area and pore volume) determine the catalytic activity. The molecular size of the reactants and products determine the acetalization ability of a particular ketone. The hydrophobicity of the various rare earth exchanged Mg–Y zeolites, K-10 montmorillonite clay, and cerium exchanged montmorillonite (which shows maximum activity) is more determinant than the number of active sites present on the catalyst. The optimum number of acidic sites as well as dehydrating ability of Ce3+-montmorillonite and K-10 montmorillonite clays and various rare earth exchanged Mg–Y zeolites seem to work well in shifting the equilibrium to the product side.Cochin University of Science and Technolog
Analysis of morphometric characters of Selar kalla (Cuvier)
92-93Relationships between different morphometric characters of S. kalla are studied. The total length is found to vary linearly with other characters. Variations in different characters are proportional to the size of the characters