Carbon dioxide, supercritical, enzymatic reaction

Nakamura, K. Hoshino, T. Novel Utilization of Supercritical Carbon Dioxide for Enzymatic Reaction in Food Processing. In Advances in Food Engineering Singh, R. P., Wirakartakusumah, M. A., Eds. CRC Press Boca Raton, FL, 1992 pp. 257-262. 

The use of supercritical carbon dioxide for enzymatic reactions is limited by the difficulty of dissolving relatively polar substrates. To increase the solubility of polar compounds, Castillo et al. [84] complexed the substrate with phenylboronic acid or immobilized polar reactants on silica gel. As model reaction the esterification of oleic acid with... 

The employment of catalytic methodologies - homogeneous, heterogeneous and enzymatic - in water or supercritical carbon dioxide as the reaction medium holds much promise for the development of a sustainable chemical manufacturing industry. Water is cheap, abundantly available, non-toxic and non-inflammable and the use of aqueous biphasic catalysis provides an ideal basis for recovery... 

Albrycht M, Kielbasinski P, Drabowicz J, Mikolajczyk M, Matsuda T, Harada T, Nakamura K (2005) Supercritical carbon dioxide as a reaction medium for enzymatic kinetic resolution of F-chtral hydroxymethanephosphinates. Tetrahedron Asymmetry 16 2015-2018... 

Bernard, P. Barth, D. Enzymatic Reaction in Supercritical Carbon Dioxide Internal Mass Transfer Limitation. High Pressure Chem. Eng. 1996, 12, 103-108. 

Dumont, T. Barth, D. Corbier, C. Branlant, G. Perrut, M. Enzymatic Reaction Kinetic Comparison in an Organic Solvent and in Supercritical Carbon Dioxide. Biotechnol. Bioeng. 1992, 39, 329-333. 

Kamat, S. Critchley, G. Beckman, E. J. Russell, A. J. Biocatalytic Synthesis of Acrylates in Organic Solvents and Supercritical Fluids HI. Does Carbon Dioxide Covalently Modify Enzymes Biotechnol. Bioeng. 1995, 46, 610-620. Kamihira, M. Taniguchi, M. Kobayashi, T. Synthesis of Aspartame Precursors by Enzymatic Reaction in Supercritical Carbon Dioxide. Agric. Biol. Chem. 1987, 51, 3427-3428. 

In biphasic reactors or two-phase partitioning bioreactors (TPPB), the substrate is located mostly in the immiscible phase and diffuses to the aqueous phase. The enzyme catalyzes conversion of the substrate at the interface and/or in the aqueous phase. The product/s of the reaction then may partition to the organic phase. The system is self-regulated, as the substrate delivery to the aqueous phase is only directed by the partitioning ratio between the two phases and the enzymatic reaction rate [53]. The use of ionic liquid/supercritical carbon dioxide for enzyme-catalyzed transformation is gaining attention [69]. 

H.J. Doddema, et al. Enzymatic reactions in supercritical carbon dioxide and integrated product-recovery. 5th European Congress on Biotechnology, Christiansen et al. (eds.), Copenhagen, 1990. 

Supercritical Carbon Dioxide as a Medium for Enzymatically Catalyzed Reaction... 

The present work reports results and observations on the enzymatic synthesis of oleyl oleate (which is a synthetic analogue of jojoba oil) in supercritical carbon dioxide. Special stress was laid on the comparison between batch and continuous systems for the above mentioned synthesis. Influence of different reaction parameters on the reaction yield and initial reaction rates was studied. 

Reaction performance. Supercritical carbon dioxide was used as a reaction media for the enzymatic synthesis of oleyl oleate directly from oleic acid and oleyl alcohol. Reaction was catalyzed by immobilized lipase from Rhizomucor miehei-Ltpozyme IM. Reactions were carried out in the high pressure batch and continuous reactor. 

Enzymatic Reaction in Supercritical Carbon Dioxide Internal Mass Transfer Limitation... 

Enzymatic reactions in non-aqueous solvents are subjected to a wide interest. A particular class of these solvents is the supercritical fluid (1) such as carbon dioxide that has many advantages over classical organic solvents or water no toxicity, no flammability, critical pressure 7.38 Mpa and temperature 31°C, and allowing high mass transfer and diffusion rates. 

D. Combes, Enzymatic Reactions in Supercritical Carbon Dioxide, in R. N Patel (Ed.), Stereoselective Biocatalysis, Marcel Dekker, New York, Basel,... 

As evident from Fig. 8.4, an increase in the selectivity has been observed in IL/ scCOj biphasic systems media (>99.5%) with respect to scCO assayed alone (95%). These results could be explained by the use of water-immiscible ILs which have a specific ability to reduce water activity in the enzyme microenvironment. The synthetic activity of the immobilized lipase in IL/scCO biphasic systems is lower than that in scCO assayed alone. Similar results were found by Mori et al. [40] in IL/ hexane biphasic systems. These authors reported that the enzymatic membranes prepared by simple adsorption of CaLB onto the surface were more reactive than membranes prepared with ILs. As can be observed in Fig. 8.4, the initial reaction rate in the assayed IL/scCO biphasic systems increased in the following sequence [bdimim ][PF ]<[bmim ][PFg ]<[bmim ][NTfj ]<[omim ] [PF ], which was practically in agreement with flie activity sequence reported by these authors using free Candida antarctica lipase B in homogeneous ionic liquid systems ([bmim ] [PF ]<[bdmim+][PFg ]<[bmim+][NTfj ]<[omim ][PF ]), with the exception of [bmim [PF ] and [bdimim+][PFg ]. These results were explained taking into account that biotransformation occurs within the ionic liquid phase, so substrates have to be transported from scCOj to the ionic liquid phase. The mechanism of substrate transport between the ionic liquid and the supercritical carbon dioxide could be by three consecutive steps diffusion of the substrates through the diffusion... 

Hemdndez FJ, de los Rfos AP, Gomez D et al (2007) Understanding the chemical reaction and mass-transfer phenomena in a recirculating enzymatic membrane reactor for green ester synthesis in ionic Uquid/supercritical carbon dioxide biphasic systems. J Supercrit Flitids 43 303-309... 

Kamat et al. dlso support this hypothesis [18]. They compared lipase-catalyzed transesterification rates in supercritical carbon dioxide, fluoroform, ethylene, ethane, propane, and sulfur hexafluoride as well as in several conventional liquid solvents of different polarities. The reaction rates increased with increasing hydrophobicity of solvent within the SCFs and also within the liquid solvent group. Because the solvent s immiscibility with water and its apolarity, by themselves, are irrelevant to enzymatic activity [8], it appears that the activity loss is the result of the enzyme losing essential water. Although SCCO2 is generally considered to be a hydrophobic solvent, it is more hydrophilic than fluoroform or hexane and capable of stripping essential water from the enzyme in an essentially nonaqueous environment. 

Heise, Palmans, de Geus, Villarroya and their collaborators (17,41,42) have been working on a chemoenzymatic cascade synthesis to prepare block copolymers. They combine enzymatic ring-opening polymerization (eROP) and atom transfer radical polymerization (ATRP). The synthesis of block copolymers was successful in two consecutive steps, i.e., eROP followed by ATRP. In the one-pot approach, block copolymers could be obtained by sequential addition of the ATRP catalyst, but side reactions were observed when all components were present from at the onset of reactions. A successful one-pot synthesis was achieved by conducting the reaction in supercritical carbon dioxide. 

We investigated the chemoenzymatic synthesis of block copolymers combining eROP and ATRP using a bifunctional initiator. A detailed analysis of the reaction conditions revealed that a high block copolymer yield can be realized under optimized reaction conditions. Side reactions, such as the formation of PCL homopolymer, in the enzymatic polymerization of CL could be minimized to < 5 % by an optimized enzyme (hying procedure. Moreover, the structure of the bifunctional initiator was foimd to play a major role in the initiation behavior and hence, the yield of PCL macroinitiator. Block copolymers were obtained in a consecutive ATRP. Detailed analysis of the obtained polymer confirmed the presence of predominantly block copolymer structures. Optimization of the one-pot procedure proved more difficult. While the eROP was compatible with the ATRP catalyst, incompatibility with MMA as an ATRP monomer led to side-reactions. A successfiil one-pot synthesis could only be achieved by sequential addition of the ATRP components or partly with inert monomers such as /-butyl methacrylate. One-pot block copolymer synthesis was successful, however, in supercritical carbon dioxide. Side reactions such as those observed in organic solvents were not apparent. 

Supercritical fluids are highly compressed gases that combine properties of gases and liquids in an intriguing manner. They have solvent power similar to light hydrocarbons for most solutes. Supercritical carbon dioxide (SCCO2) as such or as a cosolvent is a common supercritical fluid for enzymatic reactions (12). A limitation for the normal laboratory use is the need for high pressure equipment. 

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