1,721,051 research outputs found
Inorganic Materials as Supports for Covalent Enzyme Immobilization: Methods and Mechanisms
No full textSeveral inorganic materials are potentially suitable for enzymatic covalent immobilization, by means of several different techniques. Such materials must meet stringent criteria to be suitable as solid matrices: complete insolubility in water, reasonable mechanical strength and chemical resistance under the operational conditions, the capability to form manageable particles with high surface area, reactivity towards derivatizing/functionalizing agents. Non-specific protein adsorption should be always considered when planning covalent immobilization on inorganic solids. A huge mass of experimental work has shown that silica, silicates, borosilicates and aluminosilicates, alumina, titania, and other oxides, are the materials of choice when attempting enzyme immobilizations on inorganic supports. More recently, some forms of elemental carbon, silicon, and certain metals have been also proposed for certain applications. With regard to the derivatization/functionalization techniques, the use of organosilanes through silanization is undoubtedly the most studied and the most applied, although inorganic bridge formation and acylation with selected acyl halides have been deeply studied. In the present article, the most common inorganic supports for covalent immobilization of the enzymes are reviewed, with particular focus on their advantages and disadvantages in terms of enzyme loadings, operational stability, undesired adsorption, and costs. Mechanisms and methods for covalent immobilization are also discussed, focusing on the most widespread activating approaches (such as glutaraldehyde, cyanogen bromide, divinylsulfone, carbodiimides, carbonyldiimidazole, sulfonyl chlorides, chlorocarbonates, N-hydroxysuccinimides)
Composizione a base di mercaptopolimeri particolarmente adatta per cromatografia e relativo procedimento di preparazione
No full textLigninolytic peroxidase-like activity of a synthetic metalloporphine immobilized onto mercapto-grafted crosslinked PVA inspired by the active site of cytochrome P450
No full textA synthetic metalloporphine was immobilized onto a PVA-based and mercapto-grafted solid support, emulating the active site of cytochrome P450. Its ligninolytic peroxidase-like catalytic activity was studied. The coordinated mercapto ligand significantly affected the catalytic features of the catalyst because the oxidation of lignin-model compounds was very slow by comparison with imidazole-and pyridine-coordinated immobilized metalloporphines. Conversely, the catalyst efficiently bleached several industrial dyes and thus demonstrated promising activity for this application. Based on this altered substrate specificity the oxygen-donor catalytic route seems to be more favorable than a single electron oxidation pathway
Some aspects of tyrosine secondary metabolism
No full textThe origin and fate of some tyrosine secondary metabolites within specialized eukaryotic cells are discussed in the light of our knowledge of the plasma environment to which they are exposed throughout their lifetime. Attention is focused on ar-dihydroxy and -trihydroxy derivatives and the corresponding quinoidal counterparts, as well as on the enzymic activities involved in the formation and degradation of these potentially toxic molecules. Some physiopathological and pharmacological implications of the above-mentioned topics are considered, taking into account the well known toxicity of reactive intermediates in molecular oxygen reduction, as well as the reactivity of both semiquinonic and quinonic products of catecholamine oxidation
Irreversible affinity immobilization of lentil seedling amine oxidase with activity retention
No full textAn aliphatic-amine-bearing chromatographic support, based on commercial silica, was prepared and tested as potential matrix for affinity immobilization of a copper/topaquinone-containing amine oxidase from lentil seedlings. The support proved to be noticeably effective in immobilizing the enzyme with concomitant purification and activity retention. The immobilization yields and some properties of this preparation were also determined and compared with those of the soluble enzyme. High activity retention, good operational stability and low preparative costs are best combined in this promising immobilized amine oxidase
Characterisation of Accurel MP 1004 polypropylene powder and its use as a support for lipase immobilization
No full textAccurel MP1004, a porous polypropylene powder, was characterised for lipase immobilisation. The particle size ranges
between 40–80 mesh, corresponding to particle diameters of 177–420m. The pore distribution falls between macroporous
and mesoporous domains. A crude lipase preparation from Mucor javanicus was immobilised on Accurel MP1004 by adsorption.
During the adsorption process, by measuring the variation of pore volume and of pore size distribution of mesopores as
a function of enzyme loading, a significant penetration of the enzyme molecules into the pores was found to occur.
The various proteins in the crude lipase preparation are quickly adsorbed by the Accurel MP1004. However, they are progressively
displaced by the lipase which shows a greater affinity for the support.Atransesterification reaction, between glycerol
tricaprylate and 1-butanol in solvent-free conditions, was catalysed by the lipase before and after the immobilisation process.
The immobilisation on Accurel MP1004 improves the lipase performance both in terms of activity and of substrate conversion
Laccase from Pleurotus sajour caju on functionalised mesoporous silica: immobilisation and use for the oxidation of phenolic compounds
No full textLaccase from Pleurotus sajor-caju was immobilised on functionalised SBA-15 mesoporous silica. The immobilisation process reached the equilibrium after about 100 min. In order to study the effect of loading (L) on activity of the immobilised laccase, the adsorption isotherm was built and the activity of the corresponding immobilised biocatalysts was determined. The activity of the immobilised preparations reached a maximum at L = 217 kU g(SBA-15)(-1), whereas higher loadings gave rise to a less-efficient biocatalyst. The immobilized laccase was used for the oxidation of a mixture of four phenolic compounds (protocatechuic acid, ferulic acid, sinapic acid and caffeic acid) chosen among those present in olive mill wastewaters (OMWs). These compounds determine the phytotoxicity of OMWs. Different reaction rates were observed for the oxidation of the examined phenolic compounds. The biocatalyst was recycled and a conversion of 84 mol% at the 10th reuse and of about 60 mol% after the 14th reuse was obtained. In conclusion, the laccase immobilised on SBA-15 is a potential biocatalyst for bioremediation of OMWs, which is an important environmental problem in the regions around the Mediterranean Sea. (C) 2008 Elsevier B.V. All rights reserved
Olive milling wastewater as a medium for growth of four Pleurotus species
No full textFour species of Pleurotus were adapted to grow on olive milling wastewater, and in certain conditions produced high yield of fruit bodies. Some biochemical transformations were observed in the olive milling wastewater owing to the growth of Pleurotus. In particular, the fungi actively excreted large amounts of laccase in the medium, and at the same time the concentration of phenolics and other toxic compounds significantly decreased, as revealed by HPLC analysis and toxicity tests on standard cultures of human cell line
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