ILs-Solvents for Sustainable Technology in Biocatalysis

ILs represent a new class of salts that are distinguished by a range of useful properties such as negligible vapor pressure, thermal stability, non-flammabiHty, a high ionic conductivity, and remarkable solubility properties and have rapidly found a 

The properties and behavior of the IL can be adjusted separately for each individual reaction and, therefore, they can be described as designer solvents. By choosing the correct IL, high product yields can be obtained and a reduced amount of waste can be produced in a given reaction. Often the IL can be recycled and this leads to a reduction in the costs of the processes. Reactions in ILs are not difficult to perform and usually require no special apparatus or methodologies. The reactions are often quicker and easier to carry out than in conventional organic solvents. 

Several thermodynamic and kinetic behaviors of enzyme-catalyzed reactions performed in ILs, with respect to enzymatic reactions carried out in conventional solvents, could lead to an improvement in the process performance [34—37]. ILs showed an over-stabilization effect on biocatalysts [38] on the basis of the double role played by these neoteric solvents ILs could provide an adequate microenvironment for the catalytic action of the enzyme (mass transfer phenomena and active catalytic conformation) and if they act as a solvent, ILs may be regarded as liquid immobilization supports, since multipoint enzyme-1L interactions (hydrogen. Van der Waals, ionic, etc.) may occur, resulting in a flexible supramolecular not able to maintain the active protein conformation [39]. Their polar and non-coordinating properties hold considerable potential for enantioselective reactions since profound effects on reactivities and selectivities are expected [40]. In recent years attention has been focused on the appUcation of ILs as reaction media for enantioselective processes [41—43]. 

Extraction of the product from the IL in pure form can pose a problem. Water soluble compounds can be easily extracted with water. For separation of compounds with high vapor pressure the distillation could be used and higher temperatures would be required in order to extract products with low vapor pressures, which could result in decomposition of the product. 

The influence of different ILs, based on N, N dialkyUmidazolium cations as reaction media, on the enantioselectivity of commercially available immobilized lipase from CALB for the kinetic resolution of 1-phenylethanol was studied. Further, the performance of the enzymatic kinetic 1-phenylethanol resolution by CALB in the system [bmim][PF6]/SC-C02 was studied. 

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