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The thermal stability of Candida rugosa (C. rugosa) lipase was investigated and compared in n-hexane, benzene, dibutyl-ether as well as [bmim]PF6 and [omim]PF6 ionic liquids and the effect of solvent polarity and water activity were evaluated. Deactivation of the enzyme followed a series-type kinetic model. First order deactivation rate constants and the ratios of specific activities were determined and the kinetics of deactivation were studied. Among the organic solvents, the best stability was observed in n-hexane with a half-life of 6.5?h at water activity of 0.51. In ionic liquids, however, even longer half lives were obtained, and the enzyme was stable in these solvents at 50°C. The highest half-life times were obtained in [bmim]PF6 (12.3?h) and [omim]PF6 (10.6?h). A direct correlation was found between solvent polarity and thermal stability since the higher the polarity of the solvent, the lower was the stability decrease at 50°C comparing to that at 30°C. 相似文献
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Hydrolysis of triolein in AOT/isooctane reversed micelles by an sn-1,3-regioselective and a non-selective lipase were studied. Kinetics of the multistep reaction: decomposition of tri-, di- and monoacylglycerols and production of fatty acid were investigated separately. All the reactions was found to obey the Michaelis-Menten model and the apparent parameters (Michaelis-constants (Km) and maximal reaction rates (Vmax)) were determined both for non-selective and regioselective preparations. 相似文献
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Glucoamylase was produced extracellularly by fermentation of strain Aspergillus awamori, which had been genetically modified to have high-level glucoamylase activity. Initial experiments showed that the enzyme deactivated quickly, with a half-life of less than 6 days even stored at 5°C. A possible reason for the rapid deactivation was the presence of proteases, attacking and degrading the glucoamylase. Therefore a liquid protease inhibitor cocktail (Sigma, USA) was selected and applied to enhance the stability of the enzyme. The activity of the enzyme (stored at 5°C) measured by the Schoorl-method with starch as substrate showed that the cocktail was effective with the enzyme maintaining 95% of its initial storage activity for almost one year. The enzyme preparation has been used for starch hydrolysis in a flat-sheet membrane bioreactor at 60°C to manufacture glucose solution and its operation stability extended by using the cocktail. 相似文献
4.
K. Bélafi-Bakó F. Kovács L. Gubicza J. Hancsók 《Biocatalysis and Biotransformation》2013,31(6):437-439
Methanolysis (transesterification with methanol) of sunflower oil by lipase from Candida antarctica (Novozym 435) in a solvent-free system has been studied. Stepwise as well as continuous methanol feeding was applied to avoid strong substrate inhibition. Glycerol was found to cause strong product inhibition on the enzymatic reaction, therefore glycerol removal by dialysis was investigated using a flat sheet membrane module. 相似文献
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Findrik Z Németh G Gubicza L Bélafi-Bakó K Vasić-Rački D 《Bioprocess and biosystems engineering》2012,35(4):625-635
In this paper esterification of ethanol and lactic acid catalyzed by Candida antarctica B (Novozyme 435) in ionic liquid (Cyphos 104) was studied. The influence of different variables on lipase enantioselectivity
and lactic acid conversion was investigated. The variables investigated were ionic liquid mass/lipase mass ratio, water content,
alcohol excess and temperature. Using the Design Expert software 23 factorial experimental plan (two levels, three factors) was performed to ascertain the effect of selected variables and their
interactions on the ethyl lactate enantiomeric excess and lactic acid conversion. The results of the experiments and statistical
processing suggest that temperature and alcohol excess have the highest effect on the ethyl lactate enantiomeric excess, while
temperature and water content have the highest influence on the lactic acid conversion. The statistical mathematical model
developed on the basis of the experimental data showed that the highest enantiomeric excess achieved in the investigated variable
range is 34.3%, and the highest conversion is 63.8% at the initial conditions of water content at 8%; 11-fold molar excess
of alcohol and temperature at 30 °C. 相似文献
6.
Hydrolysis of olive oil into fatty acids by lipase in a flat membrane module is reported. Lipase was immobilized by adsorption onto a hydrophilic cellulose acetate membrane. Hydrolysis was carried out by circulating pure olive on the enzyme side of the membrane and water phase on the other side. Conversion reached 85 % after 50 hours reaction time. 相似文献
7.
Zvjezdana Findrik Gergely Németh Đurđa Vasić-Rački Katalin Bélafi-Bakó Zsófia Csanádi László Gubicza 《Process Biochemistry》2012,47(12):1715-1722
This paper focuses on enzymatic esterifications in non-conventional media (organic solvents, ionic liquids, and solvent-free systems) with reference to the water removal. Different types of water removal techniques are reviewed with a special emphasis on pervaporation. Pervaporation is a separation process in which liquid is transported through a selective membrane with simultaneous evaporation of permeates. In an integrated process where pervaporation is coupled with a bioreactor where esterification is performed, selective removal of water or other esterification products can be achieved. In this manner benefit can be doubled, due to the equilibrium shift and possible pure product recovery. Available literature on esterifications coupled with pervaporation is presented in detail. Reviewed examples are divided according to the type of reaction media. 相似文献
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