| 1. |
- Adlercreutz, Patrick, et al.
(författare)
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Enzymatic conversions of polar lipids. Principles, problems and solutions
- 2001
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Ingår i: Journal of Molecular Catalysis - B Enzymatic. - 1381-1177. ; 11:4-6, s. 173-178
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Forskningsöversikt (refereegranskat)abstract
- This text provides a brief overview of the principles of enzymatic lipid conversion and some recent advances in the enzymatic conversion of glycerophospholipids and galactolipids. Lipases and phospholipases are used to exchange fatty acids or the polar group in the lipids. The reactions can be carried out either as hydrolysis-esterification sequences or as one-step transferase reactions. The scope and limitations of the different methods are discussed.
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| 2. |
- 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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| 3. |
- Lyberg, Ann-Marie, et al.
(författare)
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Enzymatic and chemical synthesis of phosphatidylcholine regioisomers containing eicosapentaenoic acid or docosahexaenoic acid
- 2005
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Ingår i: European Journal of Lipid Science and Technology. - : Wiley. - 1438-7697 .- 1438-9312. ; 107:5, s. 279-290
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Tidskriftsartikel (refereegranskat)abstract
- Regioselective incorporation of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) into phosphatidylcholine (PC) was carried out using enzymatic and chemical synthesis. Incorporation at the sn-1 position was successfully achieved by lipase-catalysed esterification of 2-palmitoyl-lysophosphatidylcholine (LPC), although in most cases, the enzymes incorporated EPA and DHA at lower rates than other fatty acids. For the incorporation of DHA, Candida antarctica lipase B was the only useful enzyme, while incorporation of EPA was efficiently carried out using either this enzyme or Rhizopus arrhizus lipase. The highest yields in the lipase-catalysed reactions were obtained at the lowest water activity (close to 0). However, by carrying out the reactions at a higher water activity of 0.22, more EPA and DHA were incorporated. Esterification of 2-palmitoyl-LPC with pure EPA at this water activity converted 66 mol-% of LPC to PC using Rhizopus arrhizus lipase as catalyst. When the fatty acid was DHA and the catalyst Candida antarctica lipase B, 45 mol-% of PC was obtained. For incorporation of EPA and DHA at the sn-2 position, phospholipase A(2) was used, but the reaction was very slow. Chemical coupling of 1 -palmitoyl-LPC and EPA or DHA was more efficient, resulting in complete conversion of LPC.
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| 4. |
- Mbatia, Betty, et al.
(författare)
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Enzymatic oil extraction and positional analysis of omega-3 fatty acids in Nile perch and salmon heads
- 2010
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1873-3298 .- 1359-5113. ; 45:5, s. 815-819
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Tidskriftsartikel (refereegranskat)abstract
- The use of commercial proteases, bromelain and Protex 30L for oil extraction/recovery of polyunsaturated fatty acids (PUFA) from Nile perch and salmon heads was evaluated. Four phases were obtained after hydrolysis, oily phase, emulsion, aqueous phase and sludge. An increase in water content during the hydrolysis resulted in a decrease in oil yield. Maximum oil yield was obtained when hydrolysis was performed with Protex 30L at 55 C, without pH adjustment or water addition. An oil yield of 11.2% and 15.7% of wet weight was obtained from Nile perch and salmon heads, respectively, compared to 13.8% and 17.6%, respectively obtained using solvent extraction. Fatty acid distribution analysis showed 50% of palmitic acid was in sn-2 position in Nile perch triglycerides (TAG), while only 16% of this fatty acid was in sn-2 position in salmon oil TAG. (C) 2010 Elsevier Ltd. All rights reserved.
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| 5. |
- Adlercreutz, Patrick
(författare)
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Activation of enzymes in organic media at low water activity by polyols and saccharides
- 1993
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Ingår i: BBA - Protein Structure and Molecular Enzymology. - 0167-4838. ; 1163:2, s. 144-148
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Tidskriftsartikel (refereegranskat)abstract
- Horse liver alcohol dehydrogenase and α-chymotrypsin were deposited on a porous support material, Celite. After equilibration at a well-defined water activity, the catalytic activity was measured with diisopropyl ether as reaction medium. The effects of the presence of polyols and simple saccharides in the preparations were investigated. The additives caused a considerable increase in the amount of water bound to the preparation at a fixed water activity. At low water activities the catalytic activity was increased and at high water activity it was decreased by the additives. The presence of additives increased the ratio of alcoholysis-to-hydrolysis activity of chymotrypsin.
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| 6. |
- Adlercreutz, Patrick, et al.
(författare)
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Aspects of biocatalyst stability in organic solvents
- 1987
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Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422. ; 1:2, s. 99-108
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Forskningsöversikt (refereegranskat)abstract
- The stability of biocatalysis in systems containing organic solvents is reviewed. Among the examples presented are homogeneous mixtures of water and water-miscible organic solvents, aqueous/organic two-phase systems, solid biocatalysts suspended in organic solvents, enzymes in reverse micelles and modified enzymes soluble in water immiscible solvents. The stability of biocatalysts in organic solvents depends very much on the conditions. The hydrophobicity or the polarity of the solvent is clearly of great importance. More hydrophobic solvents (higher log P values) are less harmful to enzymes than less hydrophobic solvents. The water content of the system is a very important parameter. Some water is essential for enzymatic activity; however, the stability of enzymes decreases with increasing water content. Mechanisms of enzyme inactivation are discussed.
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| 7. |
- Adlercreutz, Patrick
(författare)
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Asymmetric reduction of ketones with enzymes from acetic acid bacteria
- 1991
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Ingår i: Biotechnology Letters. - 0141-5492. ; 13:4, s. 229-234
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Tidskriftsartikel (refereegranskat)abstract
- Six strains of acetic acid bacteria were evaluated with respect to their capability to catalyze the stereoselective reduction of ketones. The cells were permeabilized before the bioconversions. The best strains were Gluconobacter oxydans DSM 50049 and Acetobacter aceti DSM 2002. Using either of these two strains it was possible to reduce all 12 ketones to (S)-alcohols with an enantiomeric excess of ≥94 %. The highest level of enzymatic activity was found in Acetobacter aceti DSM 2002.
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| 8. |
- Adlercreutz, Patrick, et al.
(författare)
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Characterization of Gluconobacter oxydans immobilized in calcium alginate
- 1985
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Ingår i: Applied Microbiology and Biotechnology. - 0175-7598. ; 22:1, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- Gluconobacter oxydans cells were immobilized in calcium alginate and the preparation was used for the oxidation of glycerol to dihydroxyacetone. The characterization was done according to the guidelines given by the Working Party on Immobilized Biocatalysts of the European Federation of Biotechnology. The pH optimum of the preparation was found to be 5.0 and the temperature optimum was 40°C. However, the operational stability was better at 30°C. The glycerol concentration required to obtain half the maximal reaction rate was about 5 mM for both immobilized and free cells. At low concentrations of glycerol and high concentrations of dihydroxyacetone a slight inhibition was noted. No loss of activity of the immobilized preparation was observed after storage for 68 days at +4°C. Investigation of the operational stability revealed a half-life of 5 days. Studies of the influence of particle size and cell densities as well as that of oxygen concentration revealed that the oxygen supply was the rate limiting step.
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| 9. |
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| 10. |
- Adlercreutz, Patrick
(författare)
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Cofactor regeneration in biocatalysis in organic media
- 1996
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Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 14:1, s. 1-30
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Forskningsöversikt (refereegranskat)abstract
- Methods used for the regeneration of cofactors in organic media are reviewed. Substrate-driven regeneration methods include the use of a second substrate of the same enzyme and the use of a second enzyme and its substrate. The use of mediators in oxidoreductions is described and examples of photochemical and electrochemical regeneration methods are presented. General problems and possibilities of cofactor regeneration in organic media are discussed.
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