Enzymes and Flavour Biotechnology

There are about 25,000 enzymes present in nature and about 400 have been commercialised mainly for stereoselective organic synthesis and also for the biotechnological production of flavour compounds. The worldwide market for enzymes is more than US 1 billion. 

The majority of enzymes in food biotechnology comprise hydrolytic enzymes, transferases, oxireductases and lyases. 

Microbial enzymes play the greatest role in production of flavour compounds they can also be expressed in recombinant microorganisms. 

This chapter is not only an update of our review of 1997 [1] but also an overview of the latest development in enzyme-based flavour technology. Some aspects of the present chapter are based on the previous review [1]. 

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Schreier, P, Enzymes and flavour biotechnology, in Advances in Biochemical Engineering, R.G. Berger, Ed., Springer Verlag, Berlin, 1997, p. 51. 

Since not only the isolation from nature but also biotechnological processes (the use of microorganisms and enzymes) are a source of natural flavours [5], the term bioflavours will be used. 

These advantages have a positive influence on the economy of biotechnical manufacturing processes. In many cases expensive starting materials can be replaced by cheaper and simpler substrates of the biochemical reaction which results in a favourable cost price for the flavour extract. Compared to commodities which meanwhile include numerous biotechnical products (e.g. technical enzymes), the relatively high prices obtainable for flavour chemicals justify the relatively complicated techniques necessary for biotechnical processes. Production of flavour chemicals is, therefore, an interesting further application of biotechnology in line with e. g. the generation of pharmaceutical products. 

Biotechnology has had a significant effect on the flavour industry but two factors have limited its application to fragrance. The first is cost, as biotechnological processes are usually quite expensive. The second is selectivity. Individual enzymic reactions are very selective, but biochemical redox reactions require expensive co-factors and so the usual technique is to run whole cell fermentations so as to allow the cell s chemical factory to recycle the co-factors. However, the cell does much chemistry in addition to the reaction we wish it to do and the result is a horrendous effluent problem. In flavours, the problem is often simpler as the whole cell, e.g. a yeast cell, can be used as the product. 

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