Biocatalysis integration

Class D. The class of engineered assemblies includes systems that do not spontaneously form ordered structures under normal conditions. Their classification as SPs can be justified since elements of supramolecular interaction stfil assist the final organization. Some examples are layered assembly of complementary poly electrolytes obtained by stepwise deposition under kinetic control (cf. Chapter 19), and polymer brushes prepared by grafting a polymer chain over a SAM of an initiator [6]. Both approaches allow a fine-tuning of surface properties and patterning possibilities. Tailored performance in applications, such as biocompatibility, biocatalysis, integrated optics and electronics have been considered. Additional differences between self-assembled and engineered SPs are discussed in Section I.C. 

Cascade Biocatalysis Integrating Stereoselective and Environmentally Friendly Reactions, First Edition. 

The complexity of today s pharmaceutical compounds and an increasing awareness of the environmental impact of traditional chemical syntheses have opened the door to biocatalysis. Directed evolution is an integral tool in the development of synthetic enzymes, ensuring they are suitable for use in an industrial setting. The past success of this approach indicates that it will continue to provide many examples of safe and efficient production of chemical intermediates and medical compounds. 

A detailed review of the literature of non-enzymic catalysts is given in Comprehensive Asymmetric Catalysis eds Jacobsen, E.N., Pfaltz, A. and Yamamoto, H. Springer-Verlag, Berlin/Heidelberg, 1999. As an introductory text for post-graduate students see Catalysis in Asymmetric Synthesis, Williams, J.MJ. Sheffield Academic Press, Sheffield, UK, 1999. A comparison of biocatalysis versus chemical catalysis has also been made by Averill, B.A., Laane, N.W.M., Straathof, A.JJ. and Tramper, J., in Catalysis An Integrated Approach (eds van Santen, R.A. van Leeuwen, P.W.N.M., Moulijn, J.A. and Averill, B.A.) Elsevier, The Netherlands, 1999, Chapter 7. 

Special attention is given to the integration of biocatalysis with chemocatalysis, i.e., the combined use of enzymatic with homogeneous and/or heterogeneous catalysis in cascade conversions. The complementary strength of these forms of catalysis offers novel opportunities for multi-step conversions in concert for the production of speciality chemicals and food ingredients. In particular, multi-catalytic process options for the conversion of renewable feedstock into chemicals will be discussed on the basis of several carbohydrate cascade processes that are beneficial for the environment. 

A major aspect to be overcome in the integration of biocatalysis and chemocatalysis through cascade conversions is the lack of compatibility of the various procedures, both mutually for the many chemocatalytic reactions and between the chemocatalytic and biocatalytic conversions. This is in contrast to biocatalytic reactions, which are, by far, more mutually compatible and can be much more easily combined in a multi-step cascade, as will be shown below. 

Although the focus here is on the integration of biocatalysis with chemocataly-sis (bio-chemo cascades) for carbohydrates as renewable feedstocks, some representative examples (from laboratory to industrial scale) of both bio-bio and chemo-chemo cascades are also given below for comparison of their relative scope and limitations. 

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