Biocatalysis description

A common way to benefit from the ability to combine different molecular orbital methods in ONIOM is to combine a DFT or ab-initio description of the reactive region with a semi-empirical treatment of the immediate protein environment, including up to 1000 atoms. Due to the requirement for reliable semi-empirical parameters, as discussed in Section 2.2.1, this approach has primarily been used for non-metal or Zn-enzymes. Examples include human stromelysin-1 [83], carboxypeptidase [84], ribonucleotide reductase (substrate reaction) [85], farnesyl transferase [86] and cytosine deaminase [87], Combining two ab-initio methods of different accuracy is not common in biocatalysis applications, and one example from is an ONIOM (MP2 HF) study of catechol O-methyltransferase [88],... 

Hailing (1994). A more thorough description of the fundamental principles of biocatalysis in non-conventional media. 

In chapter 8 the most generally nsed kinetic eqnations for describing the consnmption of snbstrate as a resnlt of biocatalysis have been given and/or derived. In biocatalysis, in the absence of limitation of the rate of consnmption by diffusion of substrate, the Michaelis-Menten equation usually is a good description ... 

From different disciplines, biotechnology and biocatalysis are seen from very dif ferent angles and perspectives (Figure 1.1). Chemistry and chemists emphasize a molecularly-oriented perspective dominated by compounds and transformations, whereas chemical engineering and thus chemical engineers favor a process-oriented perspective of reactions and processes lastly, biology and its practitioners contribute a systems-oriented perspective of description at the organism level as well as in their view of evolution. 

Interestingly, this is also a good description of many (but not all) homogeneous catalysis and biocatalysis reactions. Here the reactant or the substrate first coordinates to the metal complex or to the enzyme, then a reaction occurs. Finally, the product dissociates from the catalyst and diffuses back into the solution. 

The first section of this chapter describes the usage of enzymes in technical processes and concentrates on commercially important industrial enzymes. The interested reader can find a detailed description of the industrial use of enzymes in the book, Enzymes in Industry The application of biocatalysis in industry is covered in the second section, with an emphasis on the processes employed and the resulting products. 

It should be noted that these embedding schemes are closely related to the QM/MM approaches (quantum mechanical description of the active site and molecular mechanics description of the environment) [54] which are currently widely used in the treatment of homogeneous catalysis and in particular biocatalysis [55]. It should also be mentioned that many different schemes have been proposed for embedding quantum clusters into metallic substrates... 

The basic principles of bioconversion, bioreactors and biocatalysis are introduced, together with a description of the most important biocatalyst immobilization techniques. The mass transfer phenomena involved in membrane systems are discussed along with some representative configurations of membrane bioreactors, whose behaviour can be described using a simple mathematical approach. For all the aforementioned systems the most significant parameters have been defined to estimate the system performance. 

In Part I a selection of the types of membrane reactor is presented, together with chapters on the integration of membrane reactors with current industrial processes. To summarize, in Chapter 1 (Calabro) membrane bioreactors are described from an engineering point of view, together with a straightforward description and simulation, with a simple mathematical approach, of the most important configurations and processes in which they are involved. Basic principles of bioconversion, bioreactors and biocatalysis with immobilized biocatalysts are also presented. For all the cited systems the most significant parameters are defined in order to estimate their performances. The best approaches for the preparation of... 

Though nature uses many different types of enzymes to catalyze a wide variety of different transformations, only a limited number of reaction types have been widely used in biocatalysis. An overview of the most common varieties is provided below, approximately arranged by decreasing number of published examples. Detailed descriptions are available in subsequent chapters dedicated to specific reaction types. Table 1.2 summarizes reaction types, starting materials, products, and enzymes required for the most common types of biocatalytic reactions. This provides a quick reference for retrosynthetic plarming and designing syntheses of specific molecules. 

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