| 1. |
- Fureby, Anna Millqvist, et al.
(författare)
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Acyl group migrations in 2-monoolein
- 1996
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Ingår i: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 14:2, s. 89-111
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Tidskriftsartikel (refereegranskat)abstract
- Acyl migration in 2-monoolein dissolved in solvents under conditions common in lipid modification reactions has been studied. The effects on acyl migration of solvent, incubation temperature, water activity, polar additives and solid additives have been investigated. Extensive acyl migration occured in aliphatic hydrocarbons and water-miscible alcohols under dry conditions. The acyl migration rate could be decreased in several nonpolar solvents by adding a small amount of water or an alcohol. Increasing water activity had no effect in isooctane, but decreased the acyl migration rate dramatically in methyl tert-butyl ether and methyl isobutyl ketone. Several commonly used enzyme supports catalysed acyl migration, showing that supports with surface charges could catalyse acyl migration.
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| 2. |
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| 3. |
- Fureby, Anna Millqvist, et al.
(författare)
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Glyceride synthesis in a solvent-free system
- 1996
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Ingår i: JAOCS, Journal of the American Oil Chemists' Society. - 0003-021X. ; 73:11, s. 1489-1495
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of partial glycerides in a solvent-free system has been investigated with various acyl donors and glycerol as substrates and a 1,3-specific immobilized lipase to catalyze the reaction. Capric acid was the most efficient acyl donor, compared with ethyl caprate and tricaprin. However, to obtain a high yield of dicaprin and a low amount of tricaprin, ethyl caprate was the acyl donor of choice. The composition of the product mixture was determined by the ratio of ethyl caprate to glycerol; a molar ratio of 3:1 was optimum for dicaprin synthesis. The water content in glycerol did not influence the final yield of dicaprin, but initial production of capric acid increased with increasing water content. The reaction was found to be controlled entirely by external mass transfer. The yield of diglyceride could be increased from 70 to 90% by lowering the reaction temperature, so that the diglyceride precipitated during the reaction.
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| 4. |
- Millqvist Fureby, Anna, et al.
(författare)
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Preparation of diglycerides by lipase-catalyzed alcoholysis of triglgicerides
- 1997
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Ingår i: Enzyme and Microbial Technology. - 0141-0229. ; 20:3, s. 198-206
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Tidskriftsartikel (refereegranskat)abstract
- Lipase from Penicillium roquefortii immobilized on porous polypropylene particles was used for enzymatic preparation of 1,2-diglycerides by alcoholysis in organic media. A screening of commercially available lipases showed that lipases from Penicillium species produced high amounts of 1,2-diglycerides from triglycelirles. Reaction parameters such as solvent, alcohol, water activity, and fatty acid chain length wet-e investigated. The positional selectivity of the lipase as well as the selectivity for type of glyceride specie were studied using pure isomers of the partial glycerides. The enzyme showed high selectivity for triglycerides and 1-monoglycerides and very low activity towards diglycerides. The lipase had a clear preference for the 1- and 3-positions. The highest lipase activity was observed at low water activity, but the yield increased with increasing water activity. Above all, the regio-isomeric purity of the diglycerides increased with increasing water activity. The yield of dilaurin was 75% and furthermore, 95% of the the total dilaurin was 1,2-dilaurin. Alcohol concentration and chain length of the alcohol had insignificant effect on yield and enzyme activity, but product stability increased when alcohol was present in the reaction medium. The best solvents were ethers; higher enzyme activities were obtained in aliphatic hydrocarbons bur yields and regio-isomeric purities were low presumably due to acyl migration.
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| 5. |
- Millqvist-Fureby, Anna, et al.
(författare)
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Spray-drying of trypsin – Surface characterisation and activity preservation
- 1999
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Ingår i: International Journal of Pharmaceutics. - 0378-5173 .- 1873-3476. ; 188, s. 243-253
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Tidskriftsartikel (refereegranskat)abstract
- In the present study trypsin mixed with various carbohydrates, i.e. lactose, sucrose, mannitol, a-cyclodextrin and dextrin, was spray-dried in order to investigate the effects of spray-drying on this enzyme, with particular emphasis on the effects of interactions between trypsin and the surface formed during spray-drying. The protein was strongly over-represented at the surface of the powder particles, the surface coverage ranging from 10 to 65%, depending on the amount of trypsin in the solids (0.2-5%). This indicates that the protein adsorbs at the air/liquid interface of the spray-droplets, and that this surface is largely preserved also after drying. The surface concentration of protein in the spray-dried powders could be controlled by adding a surfactant to the mixture before drying, since the surfactant adsorbs preferentially at the air/liquid interface of the spray droplets, thus expelling protein from the surface. In general, the residual activity of trypsin in these non-optimised formulations was 90% or higher, and in no case less than 82%. It was found that the loss of activity could partly be explained by inactivation of the protein adsorbed at the surface. For mannitol and sucrose, however, the level of inactivation was higher than could be explained by surface inactivation alone, and additional mechanisms must also be considered.
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| 6. |
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| 7. |
- Millqvist-Fureby, Anna, et al.
(författare)
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Surface characterisation of freeze-dried protein/carbohydrate mixtures
- 1999
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Ingår i: International Journal of Pharmaceutics. - 0378-5173 .- 1873-3476. ; 191, s. 103-114
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation freeze-drying of proteins (BSA or trypsin) together with various carbohydrates, i.e. lactose, sucrose, mannitol, a-cyclodextrin and dextrin, has been studied with particular emphasis on the surface composition of the freeze-dried powders. The proteins were found to be over-represented on the powder surface as compared to the bulk concentration of protein. The mechanism behind the surface accumulation is believed to be that proteins adsorb preferentially over carbohydrates to the ice/liquid interface in the frozen sample. The degree of surface accumulation depended on the carbohydrate used, and was increased in annealed samples compared to reference samples. The activity of trypsin was fairly preserved well (58-90%) in the freeze-dried powders, but depended on the carbohydrate excipient, whilst the surface composition had little effect on the activity. The activity preservation was improved when the protein concentration was raised from 1% to 10% in the solids. The surface composition of powders containing mixtures of mannitol and dextrin as excipients depended on the ratio between the two carbohydrates, with the lowest surface coverage of protein obtained in 50/50 mixtures.
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