Sustainable biocatalysis

Nowadays biocatalysis is a well-assessed methodology that has moved from the original status of academic curiosity to become a widely exploited technique for preparative-scale reactions, up to the point that the so-called industrial biotechnology (to which biocatalysis contributes to the most extent) is one of the three pillars of the modern sustainable chemistry. 

Important topics in biocatalysis for organic synthesis are described in this book, for experts and non-experts. Especially, the book focuses on those reactions that are under development now and will be more significant in the future. Therefore, each chapter describing a specific theme summarizes not only the present state but also the direction of the research. The prospects and dreams that will become possible, using biocatalysis, in the future to construct a sustainable society are also included. 

Biocatalysis is a main part of white biotechnology and in combination with the usage of renewable primary products should lead to a more sustainable chemical and pharmaceutical industry. 

This chapter outlines the principles of green chemistry, and explains the connection between catalysis and sustainable development. It covers the concepts of environmental impact, atom economy, and life-cycle analysis, with hands-on examples. Then it introduces the reader to heterogeneous catalysis, homogeneous catalysis, and biocatalysis, explaining what catalysis is and why it is important. The last two sections give an overview of the tools used in catalysis research, and a list of recommended books on specialized subjects in catalysis. 

Although biocatalysis is the new kid on the block, more and more companies are using enzymes for chemical manufacture. One reason for this is that biocatalysts give sustainable alternatives to chemical manufacture, and not just for making chiral products. The synthesis of acrylamide via an enzyme-catalyzed water addition to acrylonitrile (2-propenenitrile) is a classic example (Figure 1.15). It uses the Rhodo-coccus enzyme nitrile hydratase. Commercialized in 1985 by Nitto Chemicals in... 

The problem of chiral synthesis is critical in making pharmaceuticals. Researchers at GlaxoSmithKline, AstraZeneca and Pfizer have examined 128 syntheses from their own companies and found that as many as half of the drug compounds made by their process R D groups are not only chiral but also each contains an average of two chiral centers [ 15 2]. To meet regulatory requirements, enantiomeric purities of 99.5% were found to be necessary. Biocatalysis is thus an essential tool for pharmaceutical research, and contributes to the development of more sustainable processes. 

In Chapter 1 (Section 1.6.1, Bio-based Economy) it was noted how white biotechnologies contribute to sustainability. We may cite, as an additional example, that DSM s route to the antibiotic cephalexin (a combination of a fermentation and an enzymatic reaction with respect to multistep chemo-synthesis) reduces of 65% the materials and energy used, and about 50% the variable costs [153]. Other examples of biocatalysis and white biotechnologies used industrially by DSM are summarized in Table 2.5. 

Figure 2.17a reports in more detail the process simplification possible by biocatalysis in the case of cephalexin synthesis [154]. Figure 2.17b shows the results of a life cycle analysis (Chapter 5) of the old chemical route versus the new white biotech route [154]. The significant improvement in the sustainability of the new process is clearly evidenced. 

Biocatalysis is thus an active and promising area for the development of sustainable chemical syntheses at an industrial scale [186], as well as for several other interesting applications, from environmental bioremediation to bioenergy. 

This book is thus organized in three parts. The first five chapters discuss the principles and tools needed to realize a sustainable industrial chemistry. Chapter 1 discusses the general principles and emphasizes the differences between green and sustainable industrial chemistry approaches. It is also an introductory chapter to the topic. Chapter 2 discusses the role of catalysis as a main enabling factor to achieve sustainability through chemistry. Several examples of homogeneous, heterogeneous and biocatalysis are discussed, with emphasis on industrial aspects, to provide a comprehensive view of the possibilities offered by this tool. 

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