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1

Nonaqueous media ? site of enzymatic catalysis

100%
Bancerz R., Ginalska G.
Biotechnologia
|
2009
|
issue 4
168-182
EN
Lipases, esterases, acylases, glycosidases, aldolases are the most used enzymes in synthetic organic chemistry. Among the biocatalysts, lipases are the most frequently used. This class of enzymes is able to catalyze the hydrolysis of carboxylic acid esters in aqueous medium on the reverse reaction in organic solvents. The use of enzymes in organic solvents is now well established and there are several advantages of conducting enzymatic reaction in water poor media such as increased solubility of hydrophobic substrates, shifting of thermodynamic equilibrium in favour of synthesis over hydrolysis and increased thermostability of the enzyme. However, the practical application of enzyme in organic solvents has been hampered by the low catalytic activities compared to those expressed in water. This review highlights recent research on the stabilization of enzymes using both chemical and biological means to increase the lifetime o the biocatalyst.
2

Fungus lipases and their activity in the hydrolisis reaction and in the synthesis of fatty acid esters

80%
Antczak T., Krystynowicz A., Galas E.
Biotechnologia
|
1995
|
issue 2
82-91
EN
Preparations of soluble and immobilized fungus lipases showing high catalityc acivity in hydrolysis of acyloglycerols in water, synthesis of esters of higher fatty acids in hydrolysis of acyloglycerols in water and synthsis of esters of higher fatty acids inorganic solvents milieu were obtained.The course of reaction andthe activity dependedon: the lipase source, the form of enzyme and the reaction milieu.The studied extacellular lipases, in a water - soluble form (especially R.nigricans lipase), exibited high activity in olive oil hydrolisis.The lipases were not active in esters synthesis in diphase system: water-organic solvent.Being drained by liophilization they demonstrated the activity in esters synthesis inorgnic solvents milieu.The endocellular lipases immobilized in situshowed the hihgest activity in the synthesis of esters in organic milieu.These enzymes can also be used for hydrolysis of acyloglycerols.The obtained liquid and immobilized mycelial preparations demonstrate activity which qualifies them for industrial scale application.
3

Selection of reaction system for dipeptides enzymatic synthesis

80%
Trusek-Holownia A., Noworyta A.
Biotechnologia
|
2000
|
issue 1
156-170
EN
Synthesis of dipeptides in water, in the solution of water/organic cosolvent and in the binary aqueous-organic system was studied. A set of equlibrium equations was determined and used to predict a product yield. Reagents activities served as variable. Verification of equation's validity was performed in the synthesis of ZAlaPheOMe dipeptide catalysed by thermolysin. The reaction was carried out in water, metanol-water solution and in binary system ethyl acetate - water. It was shown that the synthesis in the binary system was the most effective. It was concluded that the efficiency of ethyl acetate - water system resulted from: 1) improvement of the reagents solubility; 2) product extraction into the organic phase. An insignificant difference in enzyme stability when thermolysin was immersed in water or in the ethyl acetate - water system was observed. Process kinetics in the binary system will be the aim of the next studies.
4

An optimization of esters synthesis catalysed by Mucor javanicus T45 lipase in non-water media

61%
Antczak T., Galas E.
Biotechnologia
|
1995
|
issue 2
73-81
EN
An optimization of enzymatic synthesis of esters in nonwater environment was performedby mens of a gradient method.The studies were aimed at obtaining a model synthesis of butyl oleate catalyzed by Mucor javanicus T45 lipase.Theoptimized, changed parameters were as follows:substrated mass, lipase mass and chemical activator mass (diethanoloamine) which profitably modified the essential water layer of the lipase.For the initial concentration of the substrates equal to 57-67%, in reaction environment the obtained yield of coversion of oleic acid was in the range of 90-95%. A transfer of optimized conditions of butyl oleate synthesis onto oleates of the other aliphatic alcohols, enabled elaboration of simple in performance methods of synthesisof a broad variety of esters of oleic acid and aliphatic alcohols (C2-C18).
5

Enzymatic modification of natural triacylglycerols and the properties of the obtained products

61%
Adamczak M.
Biotechnologia
|
2005
|
issue 1
131-151
EN
Structured triacylglycerols (sTAG) are chemical compounds with a precisely defined chemical and stereochemical structure whose natural nutritional and physico-chemical properties have been modified. Modified TAG can be synthesized with the application of genetic engineering, physical, chemical and enzymatic methods. Due to the demand for the precisely determined structure of the resulting sTAG, their synthesis with the use of lipases is preferred. Prepared pure fatty acids or their esters, as well as synthetic monoacid triacylglycerols are necessary for sTAG synthesis. The use of such unnatural substrates requires additional processes and is cost consuming. Additionally, it can lead to loss of valuable components present in natural oils and contribute to a decrease in the oxidative stability of the resulting products. The application of naturally occurring fats or oils can considerably simplify sTAG synthesis and reduce the costs of the processes. Recently, much attention has been paid to an assessment of nutritional properties of structured triacylglycerols or acylglycerols. The aim of this article is to present the methods of sTAG synthesis, including examples of the use of naturally occurring triacylglycerols as substrates.
6

Engineering the medium and bioreactor for biocatlysis

60%
Tramper J., Vermu? M. H.
Biotechnologia
|
1994
|
issue 1
81-94
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