Membranes immobilisation

Bellobono, I.R., P.L. Pinacci, G. Riva, and C. Lagrasta (1998). Pilot-plant photomineralization of. v-triazincs in aqueous solution, by pho-tocatalytic membranes immobilising titanium dioxide and trialkyl vanadates photocatalysts. Fresenius Environ. Bull., 7 277-288. Beltran, F.J., G. Ovejero, and B. Acedo (1993). Oxidation of atrazine in water by ultraviolet radiation combined with hydrogen peroxide. Wat. Res., 27 1013-1021. 

Bodzek M, Bohdziewicz J, Kowalska M. Preparation of membrane-immobilised enzymes for phenol decomposition. J Chem Technol Biotechnol 1994 61 231-239. 

Dot blots are used in place of ELISA for semi-quantitative or qualitative determination of membrane-immobilised antigens. In the dot blot procedure, the protein is bound directly to the membrane without an initial electrophoretic separation step the detection process is however the same as in Western blotting. 

Bellobono I R, Morazzoni F, Bianchi R, Mangone E S, Stanescu R, Costache C and Tozzi P M (2005), Laboratory-scale photomineralisation of n-alkanes in aqueous solution, by photocatalytic membranes immobilising titanium dioxide , Int J Photoenergy, 7,79-85. 

Moroni A, Bellobono I R and Gawlik B M (1999), Elementary steps of reaction pathway in the pilot plant photominerahsation of s-triazines on to photocatalytic membranes immobilising titanium dioxide and promoting photocatalysts in Froment G F and Waugh K C, Reaction Kinetics and the Development of Catalytic Processes, Elsevier Science B.V., 385-392. 

Gianturco F, Chiodaroli CM, Bellobono IR et al (1997) Pilot-plant photomineralization of atrazine in aqueous solution, by photocatalytic membranes immobilising titanium dioxide and promoting photocatalysts. Fresenius Environ Bull 6 461-468... 

Freitas dos Santos, L.M., Pavasant, P., Pistikopoulos, E.N., Livingston, A.G., Growth of immobilised cells results and predictions for membrane-attached biofilms using a novel in situ biofilm thickness measurement technique. Immobilised Cells Basics and Applications, Ed. Wijfells, R.H., Buitelaar, R.M., Bucke, C., Tramper, J., Progess in Biotech. 11, pp.290-297, 1996. 

Several L-amino acids are produced on a large scale by enzymatic resolution of N-acetyl-D,L-amino adds (Figure A8.4). Acylase immobilised on DEAE-Sephadex is for example employed in a continuous process while Degussa uses the free acylase retained in a membrane reactor. In the latter process the advantage of reuse of the enzyme and homogeneous catalysis are combined. 

Degussa AG uses immobilised acylase to produce a variety of L-amino adds, for example L-methionine (80,000 tonnes per annum). The prindples of the process are the same as those of the Tanabe-process, described above. Degussa uses a new type of reactor, an enzyme membrane reactor, on a pilot plant scale to produce L-methionine, L-phenylalanine and L-valine in an amount of 200 tonnes per annum. 

Numerous other examples of enantioselective hydrolysis of esters have been reported. For example chymotrypsin, immobilised in a liquid membrane of kerosene or cydohexane, can be used for resolution of D,L-amino add esters in an emulsion type... 

Polyazetidine prepolymer may be cross-linked in aqueous solution by reaction with amine, thiol, hydroxyl, carboxylic add or other polyazetidine groups. Cross-linking occurs upon water removal, heating or by changing to a basic pH. The immobilised cell/polymer composition may be prepared in the form of membranes, fibres, tubes or beads. 

In this case study, an enzymatic hydrolysis reaction, the racemic ibuprofen ester, i.e. (R)-and (S)-ibuprofen esters in equimolar mixture, undergoes a kinetic resolution in a biphasic enzymatic membrane reactor (EMR). In kinetic resolution, the two enantiomers react at different rates lipase originated from Candida rugosa shows a greater stereopreference towards the (S)-enantiomer. The membrane module consisted of multiple bundles of polymeric hydrophilic hollow fibre. The membrane separated the two immiscible phases, i.e. organic in the shell side and aqueous in the lumen. Racemic substrate in the organic phase reacted with immobilised enzyme on the membrane where the hydrolysis reaction took place, and the product (S)-ibuprofen acid was extracted into the aqueous phase. 

The values of the Michaelis-Menten kinetic parameters, Vj3 and C,PP characterise the kinetic expression for the micro-environment within the porous structure. Kinetic analyses of the immobilised lipase in the membrane reactor were performed because the kinetic parameters cannot be assumed to be the same values as for die native enzymes. 

The inhibition analyses were examined differently for free lipase in a batch and immobilised lipase in membrane reactor system. Figure 5.14 shows the kinetics plot for substrate inhibition of the free lipase in the batch system, where [5] is the concentration of (S)-ibuprofen ester in isooctane, and v0 is the initial reaction rate for (S)-ester conversion. The data for immobilised lipase are shown in Figure 5.15 that is, the kinetics plot for substrate inhibition for immobilised lipase in the EMR system. The Hanes-Woolf plots in both systems show similar trends for substrate inhibition. The graphical presentation of rate curves for immobilised lipase shows higher values compared with free enzymes. The value for the... 

However, there are disadvantages to using immobilised cells. The cell may contain numerous catalytically active enzymes, which may catalyse unwanted side reactions. Also, the cell membrane itself may serve as a diffusion barrier, and may reduce productivity. The matrix may sharply reduce productivity if the microorganism is sensitive to product inhibition. One of the disadvantages of immobilised cell reactors is that the physiological state of the microorganism cannot be controlled. 

Taillardat-Bertschinger, A., Carrupt, P. A., Barbato, F., Testa, B. Immobilised artifidal membrane HPLC in dmg research. 

Surface for membrane-proteins Immobilised using hydrogel... 

Wen et al. [950] used 8-hydroxyquinoline immobilised on a polyarylonitrile hollow fibre membrane to achieve a 300-fold concentration factor for rare earth elements in seawater. 

Figure 3. Components of an ion-selective electrode chemical sensor (left) and photographs of electrode body (right) showing electrode barrel with silver-silver chloride electrode, and screw-on electrode tip with end-clip for attaching the PVC membrane containing immobilised molecular receptors that will selectively bind specific target species.

L-ascorbic acid Potentiometric Based on ascorbate oxidase of natural source immobilised on ethylene-vinylacetate membrane Fernandes et al. (1999)... 

Starch Enzymatic Amyloglucosidase, mutarotase, glucose oxidase and catalase co-immobilised on either nylon net or activated collagen membrane Vrbova et al. (1993)... 

The first step in the concentrations of cations in plant roots is the transfer of the cations across the plasmalemma of the epidermal cells, and although the subsequent transfer of ions to the xylem is fairly clear (99), it is this transport across the cell membranes of the epidermis where the uncertainty occurs. Studies of the uptake of 46Sc3+ into barley roots have demonstrated that there is no significant uptake beyond the epidermis and first rank of cortical roots of the seminal roots (100). Presumably other polyvalent cations will be immobilised at the same place. 

Salminen T, Pulli A, Taskinen J (1997) Relationship between immobilised artificial membrane chromatographic retention and the brain penetration of structurally diverse drugs. J Pharm Biomed Anal 15 469-477. 

Barbato, F. (2006) The use of immobilised artificial membrane (lAM) chromatography for determination of lipophilicity. Current Computer-Aided Drug Design, 2, 341-352. 

The reaction in a homogeneous solution with a polar organic solvent in which the enzymes and substrates are both soluble, occurs often at the expense of the enzyme stability [4, 5]. Besides immobilised enzymes in organic solvents [6], emulsion reactors, especially enzyme-membrane-reactors coupled with a product separation by membrane based extractive processes [7-9] and two-phase membrane reactors [10-12], are already established on a production scale. 

Separation between the internal and external solutions of the selective electrode is achieved using a porous hydrophobic disc (of 3 mm diameter). The disc is wetted with an organic solvent that is immiscible with water on either side and contains an ionophore (Fig. 18.4). Hence, the membrane can be considered as an immobilised liquid. The counter ion is a molecule which is soluble in the organic phase. 

In some systems, for example, the immobilised enzyme is sandwiched between an external cellulose acetate membrane that blocks the passage of heavy molecules and an internal polycarbonate membrane that allows passage of the transformed products to the electrode. 

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