Immobilized form

P-amylase, and debranching enzymes. Conversion of D-glucose to D-fmctose is mediated by glucose isomerase, mosdy in its immobilized form in columns. Enzymic degradation of starch to symps has been well reviewed (116—118), and enzymic isomerization, especially by immobilized glucose isomerase, has been fiiUy described (119) (see Syrups). 

Siace the late 1980s, there has been considerable activity ia the development of fermentative approaches for the preparation of the amide from the nitrile. Organisms such as A.chromohacter (35), A.grohactenum (36), Streptomjces (37), Phodococcus (38,39), and Comebacterium (40) have been described. Purified enzymes ia either free (41) or immobilized form (42,43) have also been used ia this appHcation. 

This amide, readily formed from an amine and the anhydride or enzymatically using penicillin amidase, is readily cleaved by penicillin acylase (pH 8.1, A -methylpyrrolidone, 65-95% yield). This deprotection procedure works on peptides, phosphorylated peptides, and oligonucleotides, as well as on nonpeptide substrates. The deprotection of racemic phenylacetamides with penicillin acylase can result in enantiomer enrichment of the cleaved amine and the remaining amide. An immobilized form of penicillin G acylase has been developed. ... 

As with organic solvents, proteins are not soluble in most of the ionic liquids when they are used as pure solvent. As a result, the enzyme is either applied in immobilized form, coupled to a support, or as a suspension in its native form. For production processes, the majority of enzymes are used as immobilized catalysts in order to facilitate handling and to improve their operational stability [24—26]. As support, either inorganic materials such as porous glass or different organic polymers are used [27]. These heterogeneous catalyst particles are subject to internal and external... 

In previous papers it was shown that the enzymatic pool of Pectolyase Y23 possesses high catalytic efficiency either as free or immobilized form in solution of pectins [28, 29] and of fresh vegetable tissues [30]. According to Baldwin and Pressor [31] the following enzymatic activities were detected in the preparation PL, PG and PE. The amount of the different enzyme detected per mg of Pectolyase Y23 and the main enzyme characteristic are quoted in Table 1... 

The biotransformation process has been improved by significant advances in biochemical engineering advances in genetic and protein engineering, microbiological manipulations for the production of enzymes, and the use of biocatalysts in immobilized form and large-scale purification methods. 

Since many metallic catalysts have high adsorption affinities, we often find that certain poison molecules are adsorbed in an immobile form after only a very few collisions with the catalyst surface. In this situation, the outer periphery of the catalyst particle will be completely poisoned while the inner shell will be completely free of poison. The thickness of the poisoned shell grows with prolonged exposure to poison molecules until the pellet is completely deactivated. During the poisoning process, the boundary between active and deactivated regions is relatively sharp. 

The patent described a method for the removal of thiophenic compounds from fossil fuels, in which the reacting media might contain organic solvents. Additionally, the biocatalyst may be contacted with the fuel directly either as free enzyme or in its immobilized form. The process could, therefore, be performed either in a batch reactor or in a semi-continuous or continuous manner. Further, it may be performed either as a stand... 

In a further development, an ADH-MB-NAD/polypyrrole electrode, a platinum counter electrode and an Ag/AgCl reference electrode were assembled and covered with a gas-permeable polymer membrane to form an gaseous ethanol sensor. This appears to be the first time that a complete enzyme sensor for gaseous ethanol has been fabricated in such a manner with NAD incorporated in immobilized form. 

To elucidate the intramolecular interaction within the hybrid, CaM-PDE hybrid with EDC was immobilized onto DEAE-Sapharose, because immobilized hybrids were expected to have no interaction with each other (inter-hybrid interaction). The CaM-PDE hybrid was immobilized to DEAE-Sepharose suspended in 100 mM glycylglycine buffer (pH 7.5). In the presence of Ca2+, the CaM-PDE hybrid showed the activity change in its bound form. The activity of the CaM-PDE hybrid in the absence of Ca2+ was ca.40% as compared to that in the presence of Ca2+. The normalized modulation in the immobilized form is comparable to that in the free form, although the total modulated activity was smaller in the DEAE-Sepharose immobilized form as presented in Fig.30. These results indicate that the selfmodulation of CaM-PDE activity can be performed in its immobilized form, as this modulation was caused by the CaM moiety in the hybrid (intrainteraction). If CaM and PDE are independently present in solution, CaM has to randomly access to PDE to modulate the enzyme. However, in the case of CaM-PDE distinct CaM molecules modulates the corresponding PDE molecules in intra-hybrid interaction. In other words, CaM concentration... 

The selectivity in favor of the desired monobenzylated product was found to be >99% and the immobilized Pt02 was found to be 4-5 times more active than the commercial Adams catalysts. In solution or in immobilized form, the PtOz colloid is effective in the hydrogenation of carbonyl compounds or of olefins. Recently, the heterogeneous catalytic amination of aryl bromides by immobilized Pd(0) particles has been reported [163], Secondary amines such as piperidine and diethyl amine are used in the amination of aryl bromides and the reaction proceeds with good turnover numbers and regio-control. The catalysts can be reused repeatedly without loss of activity or selectivity after filtration from the reaction mixture. 

Lipases can catalyze hydrolysis of esters, synthesis of esters, trans-esterification, and synthesis of some polymers. They have been applied in many fields including the food industry, fine chemistry, and the pharmaceutical industry. The low stability of native lipases makes them unsuitable for industrial applications. In order to use them more economically and efficiently, their operational stability can be improved by immobilization. Numerous efforts have been focused on the preparation of lipases in immobilized forms involving a variety of both support materials and immobilization methods [278],... 

Enzymes are valuable analytical tools and offer sensitive and specific methods of quantitation for many substances. The increasing availability of highly purified enzyme preparations, both in solution and in immobilized forms, permits the development of a wide range of methods. 

The characteristics of a support material are of great importance to the measured enzyme activity [79, 101]. Hydrophobic carriers have a low ability to attract water, thus leaving more available for the enzyme, hence Wehtje et al. [102, 103] have shown that celite is a suitable carrier for the PaHnl to yield an immobilized form of the enzyme. In contrast, controlled pore glass (CPG) and Sephadex G25 were found to be less well suited to enzyme support as, using these systems, cyanohydrin synthesis was significantly reduced (over 30%). Sephadex also promoted the spontaneous addition of HCN to benzaldehyde [102]. A series of batch experiments showed that if the solvent (diisopropyl ether) surrounding the immobilised PaHnl contained insufficient water (i. e. less than 2 %), it would be extracted from the enzyme preparation and consequently enzyme activity was lost [102]. These results were the basis for the production... 

All the enzymes used in the work described above are quite stable at room temperature and can be used in a free form. They can also be used in an immobilized form to improve the stability and to facilitate the recovery. Many immobilization techniques are available today (25). The recent procedure developed by Whitesides et al using water-insoluble, cross-linked poly(aerylamide-acryloxysuccinimide) appears to be very useful and applicable to many enzymes (37). We have found that the non-crosslinked polymer can be used directly for immobilization in the absence of the diamine cross-linking reagent. Reaction of an enzyme with the reactive polymer produces an immobilized enzyme which is soluble in aqueous solutions but insoluble in organic solvents. Many enzymes have been immobilized by this way and the stability of each enzyme is enhanced by a factor of greater than 100. Horse liver alcohol dehydrogenase and FDP aldolase, for example, have been successfully immobilized and showed a marked increase in stability. 

Iron oxides are, in general, compounds with low to very low solubility. In natural systems where most of the iron is in the form of Fe oxides, the iron should, therefore, be in an immobile form. As large amounts of iron circulate in all parts of the ecosystem (biota, water and soil), however, mobilization of iron (i.e. dissolution) from the... 

Ruzicka ei al. [57,58] developed some peculiar reflectance flow-through biosensors based on a sensing microzone accommodating an enzyme and an acid-base indicator (both in immobilized form) where spacial and temporal resolution of the biochemical and chemical reaction or the reversible separation of hydrogen ions was therefore impossible. The pH sensors developed by these authors (see Section 3.5.1.1) can be regarded as precedents for these reflectance sensors. The sensing approach used relies on... 

This immunometric assay employed an analog of the analyte (T2) as a ligand of immunosorbent, as in the example discussed in Section 3.1. The authors mentioned that the use of T2 molecules having low intrinsic affinity to the antibody but high avidity in the immobilized form on the CPG, through the use of divalent binding, obviated the need to prepare a monovalent labeled antibody. 

Of the imidazolium-based IL stahonary phases (both coated and immobilized forms) that have been presented in the literature and discussed in this chapter, their utility is dependent on either the application or the desired analytes to be separated. Figure 4.4 displays a flow diagram that can be followed to choose the appropriate IL from Table 4.1. 

Hench, L. L., Clark, D. E. Campbell, J. 1984. High level waste immobilization forms. Nuclear and Chemical Waste Management, 5, 149-173. 

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