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1.
Ionic liquids as (co)solvents for enzymatic reactions
Muzafera Paljevac, Maja Leitgeb, Željko Knez, 2006, izvirni znanstveni članek

Opis: Ionic liquids are low melting point salts that represent an excitnq new class of reaction solvents. Many reactions show advantages when carried out in ionic liquids, either with regard to enhanced reaction rates, improved selectivity, or easier reuse of catalysts. To ascertain the influence of ionic liquids on the enzyme activity three different ionic liquids, 1-butyl-3-methylimidazolium chloride ([bmim] [Cl]), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF6]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) were synthesized and investigated as potential media for the hydrolysis of carboxymethyl cellulose, catalyzed by non-immobilized cellulase from Humicola insolens (Celluzyme 0,7T) and for ester synthesis, catalyzed by immobilized lipase from Rhyomucor miehei (Lipozyme RM IM). Enzyme-catalyzed reactions were performed in a batch stirred reactor at atmospheric pressure. Celluzyme 0.7T showed better activity in hydrophobic ionic liquid ([bmim] [PF6]), as compared to hydrophilic ionic liquid ([bmim] [BF4]). In the case of Lipozyme RM IM, the synthetic activity of the enzyme was strongly reduced by incubating the enzyme in ionic liquids. Paper presented at the 1st South-East European congress of chemical engineering, Belgrade, September 25-28, 2005
Ključne besede: chemical processing, ion liquids, organic salts, biotechnology, enzymatic catalysis, immobilized lipase stability
Objavljeno: 31.05.2012; Ogledov: 1278; Prenosov: 182
.pdf Celotno besedilo (360,03 KB)
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2.
Enzyme-catalyzed acylation of (R,S)-1-phenylethanol in 1-butyl-3-methylimidazolium based ionic liquids
Muzafera Paljevac, Željko Knez, Maja Leitgeb, 2009, izvirni znanstveni članek

Opis: Ionic liquids represent an exciting new class of reaction solvents for catalysis, which have been used successfully for enzyme-catalyzed reactions. In present research, three different ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl)] amide, were synthesized. They were used as a reaction medium for enzyme-catalyzed acylation of (R,S)-1- phenylethanol with vinyl acetate. Mentioned enzymatic reaction was performed in a batch stirred-tank reactor in order to optimise different reaction parameters (biocatalyst concentration, temperature, ...). The influence of three different immobilized lipases on reaction performance was studied as well. The highest reaction rate and conversion of 49.7% after 5 h of reaction performance was achieved in the case when immobilized lipase Novozym 435 from Candida antarctica was used as a biocatalyst and hydrophilic ionic liquid 1-butyl- 3-methylimidazolium tetrafluoroborate as a solvent. Therefore, the optimization of different reaction parameters on lipase- catalyzed acylation of (R,S)-1-phenylethanol was carried out in 1-butyl-3-methylimidazolium tetrafluoroborate.
Ključne besede: immobilized lipase, acylation, (R, S)-1-phenylethanol, ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate
Objavljeno: 31.05.2012; Ogledov: 1178; Prenosov: 25
.pdf Celotno besedilo (271,40 KB)
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3.
Enzymatic synthesis of isoamyl acetate with immobilized Candida antarctica lipase in supercritical carbon dioxide
M.P. Romero, L. Calvo, C. Alba, Maja Leitgeb, Mateja Primožič, Željko Knez, 2005, izvirni znanstveni članek

Opis: Isoamyl acetate was successfully synthesized from isoamyl alcohol in supercritical carbon dioxide by enzymatic catalysis. First, the impact of the acyl donor was investigated. Among several reactants, including acetic acid and two different acetates, acetic anhydride gave best yields. Then, two different immobilized lipases (Novozym 435 from Candida antarctica and Lipozyme RM-IM from Rhizomucor miehei) as biocatalysts for the above-mentionedreaction were compared. An esterification extent of 100% was obtained in continuous operation using acetic anhydride as acyl donor and Novozym 435 as enzyme. The amount of enzyme preparation was optimised to 6.25 g/mol alcohol. The effect of substrates load in the solvent was investigated. Operating at a CO2žsubstrates molar ratio below 7.0, the conversion of alcoholdecreased, probably due to an inhibitory effect on enzyme by high concentration of acetic anydride or by produced acetic acid. Pressure in the range of 8-30 MPa showed no effect on this reaction, while an increase in temperature (over 313 K) led to lower production of isoamyl acetate. Novozym 435 was very stable not finding any loss of activity during one month of continuous operation. Finally, carbon dioxide was compared to a conventional organic solvent (n-hexane). Initial reaction rate was higher in SC-CO2, although final esterification extent was similar in both media.
Ključne besede: chemical processing, high pressure technology, superkritical CO2, ester synthesis, isoamyl acetate, enzymatic catalysis, immobilized lipase, isoamyl acetate production, natural flavors
Objavljeno: 01.06.2012; Ogledov: 1265; Prenosov: 58
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