Per-Olof Larsson

Oxides of copper, ceria promoted copper, manganese and copper manganese on Al2O3 for the combustion of CO, ethyl acetate and ethanol

Combustion of CO, ethyl acetate and ethanol was studied over CuOx/Al2O3, CuOx-CeO2/Al2O3, CuMn2O4/Al2O3 and Mn2O3/Al2O3 catalysts. It was found that modification of the alumina with ceria before subsequent copper oxide deposition increases the activity for combustion of CO substantially, but the effect of ceria was small on the combustion of ethyl acetate and ethanol, The activity increases with the CuOx loading until crystalline CuO particles are formed, which contribute little to the total active surface, The CuOx-CeO2/Al2O3 catalyst is more active than the CuMn2O4/Al2O3 catalyst for the oxidation of CO but the CuMn2O4/Al2O3 catalyst is more active for the combustion of ethyl acetate and ethanol. Thermal ageing and water vapour in the feed caused a modest decrease in activity and did not affect the CuOx-CeO2/Al2O3 and CuMn2O4/Al2O3 catalysts differently. In addition, no difference in intermediates formed over the two catalysts was observed. Characterisation with XRD, FT-Raman and TPR indicates that the copper oxide is present as a copper aluminate surface phase on alumina at low loading. At high loading, bulk CuO crystallites are present as well. Modification of the alumina with ceria before the copper oxide deposition gives well dispersed copper oxide species and bulk CuO crystallites associated to the ceria, in addition to the two copper oxide species on the bare alumina. The distribution of copper species depends on the ceria and copper oxide loading. The alumina supported copper manganese oxide and manganese oxide catalysts consist mainly of crystalline CuMn2O4 and Mn2O3, respectively, on Al2O3 (C) 2000 Elsevier Science B.V. All rights reserved. (Less)

High performance liquid affinity chromatography (HPLAC) and its application to the separation of enzymes and antigens.

High Performance Liquid Afinity Chromatography (HPLAC) and its Application to the Separation of Enzymes and Antigens

A general method for the immobilization of cells with preserved viability

SummaryMicrobial, algal, plant and animal cells have been immobilized, with preserved viability, by entrapment in various matrices according to a new bead polymerization technique. The cell polymer/monomer mixture is kept suspended in a hydrophobic phase such as soy, paraffin, or silicon oil, tri-n-butylphosphate, or dibutyphtalate, which is compatible with the cells. The various monomers or polymers tested include agarose, agar, carrageenan, alginate, fibrin, and polyacrylamide. Furthermore, by adjustment of the stirring speed of the suspension, beads of desired diameter can easily be obtained. The entrapped cells are fully viable and biosynthetically active.

Covalent stabilization of alginate gel for the entrapment of living whole cells

SummaryThree methods were developed for preparing alginate gels containing cells that are stable in phosphate containing media. In Method I preformed alginate beads containing entrapped cells were treated with polyethyl eneimine followed by glutaraldehyde. In Method II alginate sol was treated with a carbodiimide and N-hydroxysuccinimide (to form active esters), mixed with cells and extruded into calcium chloride solution. The beads were subsequently cross-linked with polyethyleneimine. In Method III alginate so] was treated with periodate (to form aldehyde groups), mixed with cells and extruded into calcium chloride solution. The beads were subsequently cross-linked with polyethyleneimine. Saccharomyces cerevisiae cells, immobilized in such stabilized gels, exhibited almost the same fermentation activity as the standard preparation. The viability of the immobilized cells was retained during the stabilization procedure as judged from their ability to multiply in the presence of nutrients.The preparations remained stable in phosphate buffer for at least ten days without substantial release of cells. The extent of cross-linking was controlled by varying the time and the concentration of reactants, thus giving preparations ranging from beads with a thin stabilized shell to beads homogeneously stabilized.

Superporous agarose, a new material for chromatography

This paper reports on a new type of spherical agarose chromatography particles characterized by two sets of pores, normal diffusion pores, characteristic of all agarose materials and very wide pores, so-called superpores or flow pores. These superpores allow part of the chromatographic flow to pass through each individual particle, which gives improved mass transfer, especially in situations where diffusion is the limiting factor for the overall performance of a chromatographic separation. The particles were prepared by a double emulsification procedure. Observations under a microscope and size-exclusion chromatography were used in order to demonstrate pore flow. The chromatographic behaviour of the new particles was as efficient as that of homogeneous particles which were several times smaller. The agarose particles were derivatized with polyethyleneimine and used for an ion-exchange chromatographic separation of three model proteins. As expected from a perfusion material, the superporous beads resolved the protein mixture more efficiently than homogeneous beads of the same size.

High-Performance Liquid Affinity Chromatography of Proteins on Cibacron Blue F3G-A Bonded Silica

Abstract The reactive triazine dye, Cibacron Blue F3G-A, has been covalently attached to microparticulate porous silica and used for the resolution of a number of complementary proteins by high-performance liquid affinity chromatography (HPLAC). Cibacron Blue F3G-A was converted to its 6-aminohexyl derivative by reaction with 1,6-diaminohexane and coupled to γ-glycidoxypropyltrimethoxysilane-activated porous silica (5 μm) to generate an adsorbent containing 5.5–6.7 μmol dye/g silica. Cibacron Blue F3G-A silica columns, in conjunction with on-line monitoring of protein concentration and enzyme activity, may be exploited for the high speed fully automated resolution of dehydrogenases, isoenzymes, kinases and other proteins such as pancreatic ribonuclease A from simple or complex mixtures. The examples demonstrate the versatility of HPLAC on silica-immobilised Cibacron Blue F3G-A.

Steroid Transformation by Living Cells Immobilized in Calcium Alginate

SummaryWhole cells of Arthrobacter simplex were immobilized in a living state in calcium alginate gel. The bacteria showed steroid-Δ1-dehydrogenase activity and the production of prednisolone from cortisol was investigated. The Δ1-dehydrogenase activity of the immobilized cells could be increased about ten-fold by incubation in nutrient media (e.g., containing 0.5% peptone abd 0.2% glucose). The reason for this activation was examined and it was found that the immobilized cells were capable of multiplying when supplied with nutrients. Furthermore, provided that an inducer, cortisol, was present, the steroid-Δ1-dehydrogenase activity increased in proportion to the increase in the number of cells and it was thus concluded that microbial growth was the cause of activation.Experiments on repeated, batch-wise pseudocrystallofermentation with immobilized A. simplex cells also showed that immobilized cells could be advantageously used for pseudocrystallofermentation of steroids.

Affinity precipitation of enzymes

Bifunctional nucleotide derivatives,i.e., nucleotides connected by a spacer, such as AMP-AMP or the heterofunctionai compound AMP-ATP [ 11, have earlier been prepared with the objective of using them primarily as affinity chromatography ligands. It occurred to us that compounds of this type might function as precipitating agents for enzymes. In prirticular, dimeric NAD-derivatives should be useful since NAD has affinity for a large number of enzymes. Further, these derivatives would allow utilization of the principles of ternary complex formation, which increases the interaction and ensures a high degree of specificity [Z]. Such affinity precipitation of enzymes should not only provide a new tool in the analysis and purification of enzymes (dehydrogenases), but also be useful in morphologic and topographic studies of dehydrogenases in analogy to studies using his-biotinyl divines and avidin j33. This paper describes the preparation of a bifunctional NAD compound, N,flZ’-adipodihydrazido-bis-(Nb-carbonylmethyl-NAD) (Bis-NAD), and its properties as a complexing/precipitating agent for the tetrameric enzyme lactate dehydrogenase (LDH).

The preparation and characterisation of a water‐soluble coenzymically active dextran‐NAD+

Matrix-bound nucleotides have recently attracted considerable interest mainly due to their excellent properties as adsorbents for affinity chromatography [l-5] . The application of immobilised nucleotides as active cofactors for dehydrogenases is another aspect that is also rapidly gaining momentum. Matrix-bound nicotinamide nucleotides could be repeatedly used and would thus be attractive components in enzyme reactors and enzyme electrodes. It has been shown that NAD’ coupled to agarose [6] or glass [7] is indeed active as a cofactor, but compared with free NAD’ the efficiency is rather limited, probably due to steric problems. Considerably more favourable results are likely to be achieved with soluble carriers as polyethyleneimine [S] and dextran which allow a more unhindered interaction between the cofactor and enzyme. The present report describes the preparation and characterisation of a soluble high molecular weight derivative of NAD’, dextran-NAD’, obtained by coupling NAD’-N6 [N-(6-aminohexyl)-acetamide] to cyanogen bromide activated dextran, mol. wt. 40 000. It is coenzymically active with yeast alcohol dehydrogenase (ADH) and rabbit muscle lactate dehydrogenase (LDH) and can also recycle in a system containing both enzymes.

Alcohol production by magnetic immobilized yeast

SummarySaccharomyces cerevisiae was immobilized in calcium alginate gel together with varying concentrations of iron oxide, in the form of magnetite or a colloidal ferrite suspension, Ferrofluid™. Inclusion of magnetic material apparently had no adverse effect on the yeast cells as judged from their fermentation capacity, their operational stability as well as their ability to propagatein situ in the presence of nutrients. The usefulness of magnetic preparations in viscous or particle containing media is discussed.