Enzyme catalyzed reactions in dense gases

Knez, Željko; Habulin, Maja; Krmelj, V.

doi:10.1016/s0896-8446(98)00097-7

Cited by 65 publications

(25 citation statements)

References 39 publications

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“…This trend is in agreement with that found by Knez et al (1998) in the synthesis of oleyl oleate with Lipozyme IM in compressed gases from 40 to 60 °C under mild pressure conditions. The increase in temperature from 35 to 50 °C at constant pressure leads to a decrease in solvent density thus favoring diffusion process reducing mass transfer limitations.…”

Section: Effect Of Temperaturesupporting

confidence: 92%

Fatty acid ethyl esters production using a non-commercial lipase in pressurized propane medium

Hildebrand¹,

Rosa²,

Freire³

et al. 2009

Ciênc. Tecnol. Aliment.

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Section: Effect Of Temperaturesupporting

confidence: 92%

Fatty acid ethyl esters production using a non-commercial lipase in pressurized propane medium

Hildebrand¹,

Rosa²,

Freire³

et al. 2009

Ciênc. Tecnol. Aliment.

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“…Since the Wrst report on enzyme-catalyzed reactions in supercritical Xuids (SCFs), deWned as the Xuids above their critical temperature and pressure [6,12,18,23], much attention has been paid to the use of dense gases, mainly supercritical carbon dioxide, as potential alternatives to conventional organic solvents [1,8,14,15,20,24,27,31]. The advantages of using supercritical Xuids include the total replacement of organic solvent, coupled with higher diVusivity and lower viscosity that reduce interphase transport limitations, enhance the reaction kinetics, and tune reaction selectivity due to an appreciable increase in the local concentration of substrate and catalyst.…”

Section: Introductionmentioning

confidence: 99%

Stability and activity of lipase in subcritical 1,1,1,2-tetrafluoroethane (R134a)

Xue

et al. 2007

J Ind Microbiol Biotechnol

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The stability and activity of commercial immobilized lipase from Candida antarctica (Novozym 435) in subcritical 1,1,1,2-tetrafluoroethane (R134a) was investigated. The esterification of oleic acid with glycerol was studied as a model reaction in subcritical R134a and in solvent-free conditions. The results indicated that subcritical R134a treatment led to significant increase of activity of Novozym 435, and a maximum residual activity of 300% was measured at 4 MPa, 30 degrees C after 7 h incubation. No deactivation of Novozym 435 treated with subcritical R134a under different operation factors (pressure 2-8 MPa, temperature 30-60 degrees C, incubation time 1-12 h, water content 1:1, 1:2, 1:5 enzyme/water, depressurization rate 4 MPa/1 min, 4 MPa/30 min, 4 MPa/90 min) was observed. While the initial reaction rate was high in subcritical R134a, higher conversion was obtained in solvent-free conditions. Though the apparent conversion of the reaction is lower in subcritical R134a, it is more practicable, especially at low enzyme concentrations desired at commercial scales.

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“…The entropy of activation gives a measure of the inherent probability of the transition state, apart from energetic considerations. If ∆S f is large and negative, the formation of the transition state requires the reacting molecules to adopt precise conformations and approach one another at a precise angle (9).…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic properties of the enzymatic hydrolysis of sunflower oil in high‐pressure reactors

Primožič

Habulin

Knez

2003

J Americ Oil Chem Soc

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On the basis of our previous results, where optimal conditions for the lipase-catalyzed hydrolysis of sunflower oil in a high-pressure batch stirred tank reactor were determined, some thermodynamic and kinetic properties of lipase preparation Lipolase 100T (Aspergillus niger lipase) were established. Activation energy (32.7 kJ/mol) was determined from an Arrhenius plot. Activity of the Lipolase 100T increased between 35 and 50°C, but with further temperature increase thermal deactivation occurred. The thermal deactivation rate constant was 0.40, and the deactivation enthalpy was 123.0 kJ/mol. Because of the desirability of continuous applications of enzyme-catalyzed reactions, a high-pressure continuous flat-shape membrane reactor (HP CFSMR) was designed. Hydrolysis of sunflower oil in this reactor was performed. Maximal conversion in the HP CFSMR was achieved after 1 h. A polysulfone membrane was successfully used as a separation unit, and the highest conversion of FFA was determined at 50°C, 200 bar, and a flow rate for substrates of 0.1 mL/min (each).Paper no. J10347 in JAOCS 80, 785-788 (August 2003).

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Enzyme catalyzed reactions in dense gases

Cited by 65 publications

References 39 publications

Fatty acid ethyl esters production using a non-commercial lipase in pressurized propane medium

Fatty acid ethyl esters production using a non-commercial lipase in pressurized propane medium

Stability and activity of lipase in subcritical 1,1,1,2-tetrafluoroethane (R134a)

Thermodynamic properties of the enzymatic hydrolysis of sunflower oil in high‐pressure reactors

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