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401.
Fang-Cheng Huang Yi-Hsu Ju Cheng-wei Huang 《Applied biochemistry and biotechnology》1997,67(3):227-236
Selective hydrolysis of borage oil byCandida rugosa lipase immobilized on microporous polypropylene was carried out in an iso-octane-water two-phase system in order to obtain
glycerides rich in γ-linolenic acid (GLA). Lipase was immobilized on hydrophobic microporous polypropylene supports by physical
adsorption, γ-linolenic acid content in the unhydrolyzed acylglycerols could be raised to 51.7 mol% from an initial content
of 23.6 mol% in borage oil with a yield of 59%. A simplified kinetic model was proposed for this selective hydrolysis. The
Michaelis constantK
M
and the maximal-rate constantV
max
are 0.107M and 393.9 U/mg-protein, respectively. Product inhibition with a dissociation constant of the enzyme-product complexK
I
= 25 mM was confirmed. Some properties of the immobilized lipase were also examined. 相似文献
402.
403.
A series of enzymatically recyclable poly(ester-urethane)s consisting of a biodegradable diurethane moiety as a hard segment and an ester moiety as an enzymatically cleavable linkage was chemo-enzymatically prepared by two routes. The poly(ester-urethane) was prepared by a) the ring-opening polymerization of a cyclic ester-urethane monomer synthesized via the transesterification reaction of biodegradable diurethanediol and dicarboxylate ester using lipase and b) the direct polycondensation of a diurethanediol and a dicarboxylate ester. A significantly higher molecular-weight poly(ester-urethane) having the highest molecular weight (Mw) of 101,000 was produced by the ring-opening polymerization of the cyclic ester-urethane monomer when compared with that produced by the polycondensation of the dicarboxylate ester with diurethanediol. The poly(ester-urethane) was readily degraded by lipase into the corresponding cyclic oligomers; the oligomers were readily repolymerized by the ring-opening polymerization using lipase for chemical recycling. 相似文献
404.
Production of biodiesel from pure oils through chemical conversion may not be applicable to waste oils/fats. Therefore, enzymatic
conversion using immobilized lipase based on Rhizopus orzyae is considered in this article. This article studies this technological process, focusing on optimization of several process
parameters, including the molar ratio of methanol to waste oils, biocatalyst load, and adding method, reaction temperature,
and water content. The results indicate that methanol/oils ratio of 4, immobilized lipase/oils of 30 wt% and 40°C are suitable
for waste oils under 1 atm. The irreversible inactivation of the lipase is presumed, and a stepwise addition of methanol to
reduce inactivation of immobilized lipases is proposed. Under the optimum conditions the yield of methyl esters is around
88–90%. 相似文献
405.
本文采用微米硅球固定化猪胰脂肪酶为催化剂合成聚ε-己内酯, 以期获得具有较高分子量、 良好生物相容性和使用安全性的生物可降解医用高分子材料. 相似文献
406.
Triacylglycerols can be synthesized from glycerol and fatty acids. During this equilibrium reaction water is produced, therefore a mixture of mono-, di- and triesters is obtained. One way to produce an excess of triacylglycerols is to remove the water produced during synthesis. This can be realized in an immobilized enzyme pervaporation system. The enzyme is immobilized onto the lumen side of a cellulose membrane where the organic phase is present. Air circulates at the shell side and the water activity is controlled with the use of a condenser. The lipase catalyzed esterification of decanoic acid and partial glycerides is studied in this reactor. The system is reaction limited. Only at low water activity conditions, an excess of triacylglycerols is obtained. The enzyme activity at the start of the experiments is independent of the water activity within the range studied. Stability is influenced: After 600 hours the activity is 26% of the activity at the start at aw = 0.1 and 71% at aw = 0.45. 相似文献
407.
Jason A CarrTalal F Al-Azemi Timothy E LongJeung-Yeop Shim Cristina M CoatesEdward Turos Kirpal S Bisht 《Tetrahedron》2003,59(46):9147-9160
Pseudomonas cepacia lipase (PS-30) was used in hydrolytic resolution of 3-acetoxy-4-aryl-substituted azetidin-2-ones (>97% ee). Twenty-three β-lactam substrates with varied substituents at the C-4 center of the ring were synthesized and subjected to lipase-PS catalyzed hydrolysis in phosphate buffer (pH 7.2, 0.2 M) at 25°C. The reactions occurred with high enantioselectivity and substrate conversion. The effect of substitution on the C-4 aryl ring on lipase hydrolytic activity was dependent upon the steric and electronic nature of the substituent and its position on the aryl ring. The stereopreference of the lipase PS-30 for the (3S,4R) enantiomer was rationalized using a known active site model. Absolute stereochemistry of the enantiomers was established using single crystal X-ray crystallographic techniques. 相似文献
408.
de Castro Heizir F. Napoleão Diovana A. S. Oliveira Pedro C. 《Applied biochemistry and biotechnology》1998,(1):667-675
Several reports exist in the literature citing the decrease in conversion rates of organic-phase catalytic synthesis reactions
when acetic acid is present as a reaction component. This inhibition is thought to result from damage to either the hydration
layer-protein interaction or the overall enzyme structure. In this work, the inhibitory effect of acetic acid on lipase enzyme
activity was ameliorated by conducting syntheses under acetic acid-limiting conditions in a fed-batch system, resulting in
higher product yields. Periodic additions of acetic acid at levels of 40 mM or less gave maximum yields of 65% conversion for the reaction of citronellol and acetic acid to form citronellyl acetate.
The enzyme used was a fungal lipase fromMucor miehei, and was immobilized on macroporous synthetic resin (a Novo lipozyme Novo Nordisk, Denmark). These results represent a fourfold
improvement over batch runs reported in the literature for direct esterification of terpene alcohol with acetic acid using
lipozyme as a catalytic agent. 相似文献
409.
To provide a mathematical basis for the design and operation of a continuous, packed-bed reactor for the interesterification
of soybean oil, soybean oil that contains 22.7% oleoyl and 54.3% linoleoyl moieties as molar acyl moiety composition was interesterified
in hexane with oleic acid, using an immobilized sn-1,3-specific lipase (Lipozyme IM) from Mucor miehei. The reaction was carried out in a U-shaped Pyrex glass-made packed-bed reactor at 37°C in the following system: concentration
of soybean oil in the feed stream=12.5 wt%, molar ratio of fatty acid to soybean oil=3.0, and water content in the feed stream=1340–2340
ppm. At these water contents, Lipozyme IM gave practically the same catalytic activity, and the content of triacylglycerols
in the product oil was 91–94 wt%. Rate equations for the change in oleoyl and linoleoyl moiety compositions in soybean oil
were derived and their validity was confirmed experimentally. On the other hand, the catalytic activity of Lipozyme IM decayed
in the first-order fashion. Based on these deactivation kinetics, the flow rate of the feed stream is simulated for the operation
of a continuous, packed-bed reactor at 37°C that produces an oil of a fixed composition of oleoyl moiety. 相似文献
410.