Polymer reactions enzyme biocatalysis

Free or immobilized enzymes have been exploited already in a number of systems. Here, biocatalysis may take place in reversed micelles or in an aqueous phase in contact with an organic solvent. In a powdered state some enzymes are able to function in pure organic solvents. Furthermore, modified enzymes such as polymer bound enzymes or surfactant-coated enzymes have been developed so that they can solubilize in organic solvents to overcome diffusion limitation. The advantages of enzymatic reactions using organic solvents can be briefly summarized as follows ... 

Apart from the traditional organic and combinatorial/high-throughput synthesis protocols covered in this book, more recent applications of microwave chemistry include biochemical processes such as high-speed polymerase chain reaction (PCR) [2], rapid enzyme-mediated protein mapping [3], and general enzyme-mediated organic transformations (biocatalysis) [4], Furthermore, microwaves have been used in conjunction with electrochemical [5] and photochemical processes [6], and are also heavily employed in polymer chemistry [7] and material science applications [8], such as in the fabrication and modification of carbon nanotubes or nanowires [9]. 

It is well known that most enzymes have specific activities for their respective substrates. This substrate specificity is an advantage in enzyme-catalyzed synthesis, and many applications of biocatalysis depend on this property (L2), However, sometimes reactions between enzymes and nonsubstrate polymers are encountered. Perhaps these are side reactions discovered by accident. Perhaps these are the outcome of deliberate enzyme screening. Sometimes these reactions have low product yields or entail undesirable byproducts as such, they are unlikely to have commercial relevance. However, many of these reactions are interesting for a variety of reasons and deserve to be investigated further. 

The choice of solvents for enzymatic reaction has been widened from organic solvents to various types of solvents such as supercritical fluids, ionic liquids, etc. The enzymatic reaction in organic solvent has been reported already in 1970s, the first biocatalysis in ionic liquids [4] was in 2000, and the first biocatalysis in supercritical fluids [5] was in 1985. Currently four kinds of liquid or fluid solvents, aqueous, organic solvents, ionic liquids, and supercritical fluids, are available for biocatalysis as shown in Figure 3.2. Moreover, biphasic or triphasic solvent systems consisting of two or more kinds of the solvents are also often employed for biocatalysis. Solid phase of immobilized enzymes and/or hydrophobic polymer to adsorb substrate and product may also exist. The performance of a biocatalyst depends significantly on the solvent system. The best medium should provide optimum reaction rates and simplify work-up procedure to make the process both economical and environment friendly. 

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