Biocatalysis features

In each of these areas the relative merits of biocatalysis versus other catalytic methodologies will be assessed. Note that the text is given an asterisk ( ) when mention is made of a catalyst for a reduction or oxidation reaction that is featured in the later experimental section of this book. 

In some cases particular processes are espeeially important because of the value of the products produced and also the amounts of enzyme used, i.e. from both the enzyme producer and user standpoints. Therefore the examples on fructose syrups and 6-aminopenicillinic acid have been expanded to include much information on the business and technical strategies employed, and detailed proeess economic aspects respectively. Many other examples of biocatalysis-based commercial processes and products also exist with many others undergoing development. These other products also exhibit the same important technical and commercial features that are identified for the case studies in this chapter. 

Over the last 20 years, many reservations with respect to biocatalysis have been voiced, contending that (i) enzymes only feature limited substrate specificity (ii) there is only limited availability of enzymes (iii) only a limited number of enzymes exist (iv) protein catalyst stability is limited (v) enzyme reactions are saddled with limited space-time yield and (vi) enzymes require complicated cosubstrates such as cofactors. 

Biotechnology and biocatalysis not only differ from conventional processes by featuring a different type of catalyst but they constitute a new technology base ... 

Whereas enzymes often feature great advantages in terms of selectivity, their stability is often insufficient. Additionally, long development times of new biocatalysts owing to an insufficient knowledge base of biocatalysis and biotechnology remain a problem and a challenge. 

A century of study of metabolism in terran molecules has revealed a common core of metabolic processes through terran life. This commonality exists, in part, because of common features throughout terran genetics and biocatalysis. The core includes the tricarboxylic acid cycle, glycolysis, and synthetic pathways for construction of simple amino acids, sugars, purines, and pyrimidines. 

In the following sections some genereil features of special interest regarding elementary steps in oxidations in biocatalysis will be presented. 

Despite the limitations, the great success of enzyme immobilization in diagnostics, pharmaceutical, food and chemical industries is undeniable12, 3. The decision whether one should use a soluble enzyme preparation or an immobilized enzyme does not have a universal solution and can be decided only on a case by case basis. Ordinarily, if the cost of an enzyme represents a significant portion of the overall cost or if isolation of the final product is complicated by the presence of the soluble protein, the cost of immobilization can be offset by the gains in productivity and improved product quality. The intent of this section is to describe, in general terms with illustrative examples, the features and considerations of these broad classes of enzyme immobilization as they impact their application to biocatalysis. Detailed experimental protocols are available in the original literature and exemplary protocols for these methods are offered in many excellent reviews and texts 14L... 

Biocatalysis usually exploits advantageous features of enzymes such as chemo-selectivity, regioselectivity, enantioselecivity and substrate spectrum of a certain broadness as depicted in Fig. 16.2-1. These points are addressed in examples in the following chapters. 

There is a general need for cleaner ( green ) and sustainable chemistry, and although it is not the prerogative of biocatalysis, it is nevertheless an important feature of it. Social pressure forces the chemical industry to pay more attention to these issues, as the public becomes aware that the resources are limited and have to be used with utmost efficiency. 

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