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| 2. |
- ADLERCREUTZ, PATRICK, et al.
(author)
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Enzymatic Peptide Synthesis in Organic Media
- 1990
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In: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923 .- 1749-6632. ; 613:1, s. 517-520
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Journal article (peer-reviewed)
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| 3. |
- Bloomer, Scott, et al.
(author)
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Facile synthesis of fatty acid esters in high yields
- 1992
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In: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 14:7, s. 546-552
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Journal article (peer-reviewed)abstract
- The facile synthesis of esters by lipase-catalysed esterification of fatty acids and ethanol is demonstrated. Evaporation of the water generated in the reaction allowed the rapid production of esters of >99% yield in refluxing pentane or hexane. Water was trapped by condensing the refluxing vapor phase and passing it over activated molecular sieves in a reflux trap. High yields were rapidly obtained in synthesis of ethyl esters of oleic, linoleic, α-linolenic, and arachidonic acids without peroxidation of double bonds. The wax ester oleyl oleate was also synthesized rapidly with little peroxidation. A molar excess of 1.25 to 1.5 of ethanol allowed the most rapid ester synthesis. Synthesis of ethyl stearate was carried out on a preparative scale (50 g). Greater than 99% conversion was obtained in 50 min.
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| 4. |
- Bloomer, Scott, et al.
(author)
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Kilogram-scale ester synthesis of acyl donor and use in lipase-catalyzed interesterifications
- 1992
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In: Journal of the American Oil Chemists' Society. - 0003-021X. ; 69:10, s. 966-973
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Journal article (peer-reviewed)abstract
- Scaling up of Lipozyme-catalyzed ester synthesis with >99% conversion and a reflux trap to remove product water from the reaction mixture is reported. Ethyl stearate was synthesized in 2000-g batch reactions from technical stearic acid. The ethyl stearate was purified to 97% by crystallization and interesterified with sunflower seed oil by means of a lipase catalyst to investigate reaction parameters of temperature, substrate ratio, enzyme content and catalyst water activity. The endpoint of the reaction was defined as the incorporation of stearate into sunflower seed oil corresponding to the amount of stearate necessary to be incorporated into palm oil mid-fraction to produce a cocoa butter substitute. No tristearate was formed at the reaction endpoint in any of the reactions conducted. Reaction times decreased and levels of free fatty acids and diglycerides increased with increasing temperature and with increasing ratio of acyl donor to triglyceride. Increasing the enzyme content of the reaction mixture reduced reaction times but caused higher levels of free fatty acids and diglycerides. In reactions catalyzed by Lipozyme of defined water activity, the shortest reaction times were obtained at intermediate water activity, while free fatty acid and diglyceride levels increased with water activity. When the interesterification reaction was carried out in refluxing pentane with the condensed solvent dried by passage through a reflux trap, the free fatty acid and diglyceride levels were reduced to 6 and 3.3%, respectively.
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| 5. |
- Bloomer, Scott, et al.
(author)
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Triglyceride interesterification by lipases. 1. Cocoa butter equivalents from a fraction of palm oil
- 1990
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In: Journal of the American Oil Chemists' Society. - 0003-021X. ; 67:8, s. 519-524
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Journal article (peer-reviewed)abstract
- Twelve commercially available triacylglycerol lipase preparations were screened for their suitability as catalysts in the interesterification of palm oil mid fraction and ethyl stearate to form a cocoa butter equivalent. Five fungal lipase preparations were found to be suitable. The hydrolytic activity of the commercial lipase preparations was tested with sunflower seed oil and was independent of their interesterification activity. The operational stability of three of the preparations most suited for production of cocoa butter equivalents was examined. The amount of a commercial lipase preparation loaded onto a support was surveyed for optimum short-term catalytic activity. The influence of solvent concentration on the reaction rate and the purity of the product was examined at two temperatures. The optimum solvent concentration at 40°C was 1-1.5 grams of solvent/gram of substrate; at 60°C, the rate of interesterification diminished and the purity of the product decreased with increasing amounts of solvent. Four of the commercial lipase preparations found to be suitable interesterification catalysts were immobilized on five supports and their ability to catalyze the interesterification of a triglyceride and palmitic acid or ethyl palmitate was measured. The choice of support and substrate form (esterified or free fatty acid) greatly affected the catalytic activity. Some preparations were more affected by the choice of support, others by the form of the substrate. No preparation yielded maximum activity on all supports, and no support was found which produced an immobilized enzyme preparation of high activity with every commercial lipase preparation. Caution is advised in transferring observations about the suitability of a support from tests on one commerical enzyme preparation to others; individual testing is required.
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| 6. |
- Clapés, Pere, et al.
(author)
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Enzymatic peptide synthesis in organic media : a comparative study of water-miscible and water-immiscible solvent systems
- 1990
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In: Journal of Biotechnology. - 0168-1656. ; 15:4, s. 323-338
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Journal article (peer-reviewed)abstract
- Peptide synthesis was carried out in a variety of organic solvents with low contents of water. The enzyme was deposited on the support material, celite, from an aqueous buffer solution. After evaporation of the water the biocatalyst was suspended in the reaction mixtures. The chymotrypsin-catalyzed reaction between Z-Phe-OMe and Leu-NH2 was used as a model reaction. Under the conditions used ([Z-Phe-OMe]0 ≤ 40 mM, [ Leu-NH2]0 ([Z-Phe-OMe]0 = 1.5) the reaction was first order with respect to Z-Phe-OMe. Tris buffer, pH 7.8, was the best buffer to use in the preparation of the biocatalyst. In water-miscible solvents the reaction rate increased with increasing water content, but the final yield of peptide decreased due to the competing hydrolysis of Z-Phe-OMe. Among the water-miscible solvents, acetonitrile was the most suitable, giving 91% yield with 4% (by vol.) water. In water-immiscible solvents the reaction rate and the product distribution were little affected by water additions in the range between 0% and 2% (vol. %) in excess of water saturation. The reaction rates correlated well with the log P values of the solvent. The highest yield (93%) was obtained in ethyl acetate; in this solvent the reaction was also fast. Under most reaction conditions used the reaction product was stable; secondary hydrolysis of the peptide formed was normally negligible. The method presented is a combination of kinetically controlled peptide synthesis (giving high reaction rates) and thermodynamically controlled peptide synthesis (giving stable reaction products).
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| 7. |
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| 8. |
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| 9. |
- Kanasawud, Pawinee, et al.
(author)
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Triglyceride interesterification by lipases. 3. Alcoholysis of pure triglycerides
- 1992
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In: Enzyme and Microbial Technology. - : Elsevier BV. - 0141-0229. ; 14:12, s. 959-965
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Journal article (peer-reviewed)abstract
- Lipase-catalyzed alcoholysis of triolein dissolved in ethanol or isopropanol for the formation of ethyl and isopropyl esters was investigated. Of 16 lipases screened, Amano lipase from P. fluorescens was selected for investigation of the effects of basic reaction conditions on alcoholysis yields. Ethanolysis yields were only slightly affected by water additions to immobilized lipase preparations. Isopropyl ester yields decreased with water addition. Good operational stability was observed over 17 days. Changes in initial triolein concentration in the range 5-50 mM had very little effect on ester yields. The ionic strength of the phosphate buffer used in lipase immobilization affected ethanolysis and isopropanolysis yields in opposite ways. The highest ethanolysis yields were obtained with lipases immobilized from 250 mM buffer, while isopropyl ester yields were highest with lipases immobilized from water. In addition, the quantities and isomers of monoglyceride intermediates in ethanolysis were affected by the immobilization buffer strength. Larger quantities of 2-monoglycerides were formed in ethanolysis reactions with lipase preparations immobilized from water.
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| 10. |
- Kaul, Rajni, et al.
(author)
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Affinity precipitation
- 1993
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In: Molecular Interactions in Bioseparations. - Boston, MA : Springer US. - 0306444356 ; , s. 469-477
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Book chapter (peer-reviewed)abstract
- Precipitation and recovery of precipitates is one of the unit operations in chemical engineering that can be operated on a large scale. Experiences from the area of biotechnology have clearly shown that there is not enough selectivity in the precipitation methods used to be able to separate, for example, complex mixtures of proteins from cell homogenates. Moreover, methods to precipitate proteins with their biological functions remaining intact must be gentle. In recent years, much work has been done on improving precipitation processes, and there are, today, a few alternative strategies for the removal of cell debris by the use of efficient precipitation aids.
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