Solvents biphasic systems

Figure 5.7 Comparison of a water-organic solvent biphasic system with a micro-aqueous organic phase system...

Li, Y.-N., Shi, X.-A., Zong, M.-H. et al. (2007) Asymmetric reduction of 2-octanone in water/organic solvent biphasic system with baker s yeast FD-12. Enzyme and Microbial Technology, 40, 1305-1311. 

Figure 18 Ligands for hydroformylation in ionic liquid/organic solvent biphasic system.

Water and water-miscible solvent biphasic systems Enhanced enzyme activity and stability at low concentration Inhibitory effect on the biocatalyst at high concentration... 

Organic solvent systems include mixtures of water and water-miscible solvents, biphasic systems of water and water-immiscible solvents, pure organic solvents, and reverse micellar systems. 

One method is to run the reaction in an aqueous buffer/organic solvent biphasic system. This makes it possible to work at high substrate and product concentrations and at the pH-optimum of the enzyme. In addition, in water-immiscible solvents the non-enzymahc addition of HCN to the carbonyl group is non-existent or extremely slow. Possible disadvantages are enzyme deactivation at the interface and the presence of organic solvent dissolved in the aqueous phase [15, 17, 18]. 

Chen C-S, Wu S-H et al (1987) Quantitative analyses of biochemical kinetic resolution of enantiomers. 2. Enzyme-catalyzed esterifications in water-organic solvent biphasic systems. J Am Chem Soc 109 2812-2817... 

Catalysts immobilized on resins are quite often used for catalytic reactions. Phase-transfer conditions, guaranteeing separation and recovery of the catalysts by use of water/organic solvent biphasic systems, are another possibility. Unlike homogeneous processes, these kind of catalytic processes take account of product loss and substrate selectivity. Furthermore,... 

Biphasic systems proved to be advantageous as well in the biocatalytic synthesis of (-)-l-trimethylsilylethanol which was performed by asymmetric reduction of acetyltrimethylsilane with an isolate from Rhodotorula sp. AS2.2241 [144]. Immobilized cells were employed due to the easy separation of the product as well as the improved tolerance against unfavorable factors. In an aqueous/organic solvent biphasic system higher product yield and enantiomeric excess were achieved as compared to an aqueous monophasic system. Several organic solvents were examined, and isooctane was found to be the most suitable organic phase for the reaction. 

It would appear that some more fundamental improvements are required to make metathesis in ionic liquids sufficiently attractive rather than extracting the product, which commonly requires a large amount of conventional solvent, biphasic systems that allow decantation of the product ought to be envisaged. As metathesis reactions are often performed at elevated temperatures, ionic liquids with higher melting points could also be considered to optimise and facilitate product separation. 

Partitioning of Solutes in Water-Organic Solvent Biphasic Systems.. . 180... 

Numerous efforts 38,40,42 46 51) were undertaken to find out in what manner the aqueous solubility and the partition coefficients of different solutes in water-organic solvent biphasic systems are related to the size of the solute molecules. Since the solute packing into the solvent clearly depends on the solute surface, a relationship between surface area and solution thermodynamics seems to be reasonable. 

Since the first of the above limitations can be bypassed with an approach based on the study of partitioning of solutes in water-organic solvent biphasic systems, most of the hydrophobicity estimates for chemical compounds have been obtained by this method. 

It is known I0.43.53 ° -62> that the partition coefficients of the same solutes in various solvent biphasic systems are interrelated according to the so-called solvent regression equation ... 

He, J., Sim, Z Ruan, W., and Xu, Y. (2006) Biocatalytic synthesis of ethyl (S)-4-chloro-3-hydroxy-butanoate in an aqueous-organic solvent biphasic system using Aureobasidium pullulans CGMCC 1244. Process Biochem., 41 (1), 244-249. 

Fragnelli, M.C., Hoyos, P., Romano, D., Gandolfi, R., Alcantara, A.R., and Molinari, F. (2012) Enantioselective reduction and deracemisation using the non-conventional yeast Pichia ucozyma in water/organic solvent biphasic systems preparation of (S)-l,2-diaryl-2-hydroxyethanones (benzoins). Tetrahedron, 68, 523-528. 

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