| 1. |
- Adlercreutz, Patrick, et al.
(författare)
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Oxygen supply to immobilized cells : 1. Oxygen production by immobilized Chlorella pyrenoidosa
- 1982
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 4:5, s. 332-336
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen supply at high cell densities of aerobic organisms is a great problem in immobilized cell preparations. To investigate the possibility of in situ oxygen generation the alga Chlorella pyrenoidosa was immobilized on alginate beads. The conditions for optimal oxygen production were investigated and in long term experiments the preparations were successful for at least 30 days.
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| 2. |
- Adlercreutz, Patrick, et al.
(författare)
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Oxygen supply to immobilized cells : 2. Studies on a coimmobilized algae-bacteria preparation with in situ oxygen generation
- 1982
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Ingår i: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 4:6, s. 395-400
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Tidskriftsartikel (refereegranskat)abstract
- A coimmobilized mixed culture of algae, Chlorella pyrenoidosa, and bacteria, Gluconobacter oxydans, has been studied. The conversion of glycerol to dihydroxyacetone(1,3-dihydroxy-2-propanone), catalysed by the bacteria, was used to indicate the oxygen supply in the immobilized preparation. The oxygen produced by the algae in the coimmobilized preparation was used by the bacteria more effectively than when the cells were immobilized separately and mixed within the reactor. A preparation consisting of only bacteria and no algae was much less effective. The coimmobilized preparation was used in the continuous production of dihydroxyacetone for six days without any significant loss of activity.
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| 3. |
- Adlercreutz, Patrick, et al.
(författare)
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Oxygen supply to immobilized cells - 3. Oxygen supply by hemoglobin or emulsions of perfluorochemicals
- 1982
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Ingår i: European Journal of Applied Microbiology and Biotechnology. - 0171-1741. ; 16:4, s. 165-170
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen supply is a critical point in technical processes when aerobic cells are used in immobilized preparations. This report concerns the use of hemoglobin or emulsions of perfluorochemicals (completely fluorinated organic compounds) to carry oxygen to immobilized cells. Both methods work well and do not seem to harm the cells. The perfluorochemical method of improving oxygen supply showed a higher operational stability than the hemoglobin method.
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| 4. |
- Adlercreutz, Patrick
(författare)
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Oxygen supply to immobilized cells : 5. Theoretical calculations and experimental data for the oxidation of glycerol by immobilized Gluconobacter oxydans cells with oxygen or p‐benzoquinone as electron acceptor
- 1986
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 0006-3592 .- 1097-0290. ; 28:2, s. 223-232
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Tidskriftsartikel (refereegranskat)abstract
- Theoretical calculations of reaction kinetics were done for one‐step reactions catalyzed by cells immobilized in spherical beads. The reactions catalyzed by free cells were assumed to obey Michaelis–Menten kinetics for a one‐substrate reaction. Both external (outside the beads) and internal (inside the beads) mass transfer of the substrate were considered for the immobilized preparations. The theoretical calculations were compared with experimental data for the oxidation of glycerol to dihydroxyacetone by Gluconobacter oxydans cells immobilized in calcium alginate gel. Glycerol was present in excess so that the reaction rate was limited by oxygen. The correlation between experimental data and theoretical calculations was quite good. The calculations showed how the overall effectiveness factor was influenced by, for example, the particle size and the cell density in the beads. In most cases the reaction rate was mainly limited by internal mass transfer of the substrate (oxygen). As shown previously, p‐benzoquinone can replace oxygen as the electron acceptor in this reaction. The same equations for reaction kinetics and mass transfer were used with p‐benzoquinone as the rate‐limiting substrate. Parameters such as diffusivity, maximal reaction rate, and K were, of course, different. In this case also, the correlation between the model and the experimental results was quite good. Much higher production rates were obtained with p‐benzoquinone as the electron acceptor compared to when oxygen was used. The reasons for this fact were that p‐benzoquinone gave a higher maximal reaction rate for free cells and the solubility of p‐benzoquinone was higher than for oxygen. Different methods of increasing the rate of microbial oxidation reactions are discussed.
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| 5. |
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| 6. |
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| 7. |
- Adlercreutz, Patrick, et al.
(författare)
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Enzymatic fatty acid exchange in glycerophospholipids
- 2003
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Ingår i: European Journal of Lipid Science and Technology. - : Wiley. - 1438-7697 .- 1438-9312. ; 105:10, s. 638-645
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Forskningsöversikt (refereegranskat)abstract
- Lipases can be used to exchange fatty acids in the sn-1 position of glycerophospholipids and phospholipase A2 is useful for the corresponding exchange reaction in the sn-2 position. In both cases, the exchange can be done in a one-step acidolysis process or in a two-step process. In the latter case, the original fatty acid in the desired position is removed by enzymatic hydrolysis or alcoholysis and after isolation of the resulting lysophospholipid, the new fatty acid is introduced, using the same enzyme, in an esterification reaction. Several synthesis examples from the literature are reviewed. Incorporation of a new fatty acid into the sn-1 position is more favourable than incorporation into the sn-2 position because of the magnitudes of the equilibrium constants of the reactions and because lipases can be used at much lower water activity than phospholipase A2. With the consecutive use of both enzymes highly pure products with defined fatty acids in both positions can be obtained.
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| 8. |
- Adlercreutz, Patrick
(författare)
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Immobilisation and application of lipases in organic media.
- 2013
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Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry (RSC). - 0306-0012 .- 1460-4744. ; 42:15, s. 6406-6436
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Forskningsöversikt (refereegranskat)abstract
- Different methods of preparing lipases for use in organic media are critically reviewed. Solid lipase preparations can be made by typical immobilisation methods such as adsorption, entrapment, covalent coupling or cross-linking. Immobilisation is especially attractive for lipases because, in addition to the normal benefits of enzyme immobilisation, it can also lead to a considerable increase in catalytic activity, probably caused by conformational changes in the lipase molecules. Activation can be achieved, for example, using hydrophobic support materials or surfactants during the immobilisation procedure. Surfactants can also be used to solubilise lipases in organic media via the formation of hydrophobic ion pairs, surfactant-coated lipase or reversed micelles. Lipase preparation methods are discussed with regard to potential lipase inactivation and activation effects, mass transfer limitations, lipase stability and other features important for applications. The practical applications of lipases in organic media reviewed include ester synthesis, modification of triacylglycerols and phospholipids, fatty acid enrichment, enantiomer resolution, biodiesel production and acylation of carbohydrates and bioactive compounds.
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| 9. |
- Adlercreutz, Patrick
(författare)
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On the Importance of the Support Material for Enzymatic Synthesis in Organic Media. Support Effects at Controlled Water Activity
- 1992. - C
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Ingår i: Progress in Biotechnology. - 0921-0423. ; 8:C, s. 55-61
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Bokkapitel (refereegranskat)abstract
- Enzymes adsorbed or deposited on porous support materials have been succesfully used as catalysts in organic media. However, the support must be chosen with great care. The support can affect the partitioning of substrates, products and water in the reaction mixture and thereby indirectly influence the catalytic properties of the enzyme. Furthermore, the support can influence both the enzyme kinetics and the number of catalytically active enzyme molecules. The effects of the support on water partitioning in the system can be interpreted by measurements of the aquaphilicity (water attracting capacity) of the supports. Normally, high reaction rates are obtained with supports having low aquaphilicity. Even in experiments carried out at fixed enzyme hydration (fixed water activity) the support influences both the total activity of the enzyme and the relative rates of different reactions catalyzed by the same enzyme.
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| 10. |
- Andersson, Mats, et al.
(författare)
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Toward an enzyme-based oxygen scavenging laminate. Influence of industrial lamination conditions on the performance of glucose oxidase
- 2002
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 1097-0290 .- 0006-3592. ; 79:1, s. 37-42
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Tidskriftsartikel (refereegranskat)abstract
- The laminate consisted of several polymer layers, aluminium, and one cellulose-based layer containing the active enzymatic system (e.g., glucose oxidase, catalase, glucose, and CaCO3). During the industrial lamination process, the enzyme layer was exposed to three temperature spikes up to 325degreesC without significant enzyme inactivation. Ninety-seven percent of the glucose oxidase activity still remained after the lamination process. The best laminate had an oxygen absorbing capacity of 7.6 +/- 1.0 L/m(2). A reference that was not laminated expressed a corresponding oxygen absorbing capacity of 7.1 +/- 0.8 L/m(2).
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