Enzymatic Catalysis

Supercritical CO2 assisted synthesis and concentration of monoacylglycerides rich in omega-3 polyunsaturated fatty acids

“…This positive effect of pressure on the reaction rate has been observed in previous works with other catalysts [14] and has been also reported for Lipozyme 435 [21]. It is generally accepted that apart from the pressure-induced conformational changes in enzymes, which may take place at much higher pressures, pressure affects enzymatic reactions in two indirect ways: (1) kinetic constants change with pressure according to transition state theory and standard thermodynamics [40], and (2) reaction rates may change with the density of SCFs because physical parameters, such as the dielectric constant, change with density [41].…”

Enzymatic Reactions in High-Pressure Membrane Reactors

“…The reaction rate may change with the density of CO 2 because physical parameters, such as dielectric constant or the solubility of substrates, change with density. These changes may indirectly influence enzyme activity since the changes in dielectric constant have a significant effect on protein flexibility …”

“…The high diffusivity of SCFs and their low surface tension lead to reduced internal mass-transfer limitations for heterogeneous chemical or biochemical catalysis. SC CO 2 has been most frequently used as a supercritical medium for biotrasformations: its critical pressure (73.8 bar) is “acceptable”, and its critical temperature (31.1 °C) is consistent with the use of enzymes and/or labile solutes …”

Amphiphilic conetworks as activating carriers for the enhancement of enzymatic activity in supercritical CO2

“…RmL was chosen as biocatalyst for the present investigation. This enzyme has been frequently applied to biotransformations in scCO 2 (Aaltonen, 1999;Blattner et al, 2006), for example, for the esterification of myristic acid with ethanol (Bernard and Barth, 1995), ibuprofen with propanol (Rantakylae and Aaltonen, 1994), as well as in transesterification reactions (Chulalaksananukul et al, 1993;Liu et al, 2006). In order to prepare the RmL-loaded APCNs, 30 mm thick films of PHEA-l-PDMS as well as PHEA-l-PFPE conetworks in varying compositions were immersed into a RmL solution (16.6 mg/mL) and incubated at 48C for 14 h, followed by spectrophotometric determination of the enzyme loading.…”

“…Since the first reports on enzymatic catalysis in supercritical fluids some 20 years ago (Hammond et al, 1985;Nakamura et al, 1986;Randolph et al, 1985), these media have been broadly applied as reaction media for biotransformations (Aaltonen, 1999;Matsuda et al, 2005;Mesiano et al, 1999;Oakes et al, 2001). However, catalytic activities tend to be rather low, because enzymes are insoluble in scCO 2 , resulting in heterogeneous catalysis.…”