Disadvantages of Biocatalysts

Unfortunately, less than 10% of organic compounds crystallize as a conglomerate (the remainder form racemic crystals) largely denying the possibility of separating enantiomers by simple crystallization techniques - such as by seeding a supersaturated solution of the racemate with crystals of one pure enantiomer. 

The principle of asymmetric synthesis [76] makes use of enantiomerically pure auxiliary reagents which are used in catalytic or sometimes in stoichiometric amounts. They are often expensive and caruiot be recovered in many cases. 

Likewise, starting a synthesis with an enantiomerically pure compound which has been selected from the large stock of enantiopure natural compounds [77] such as carbohydrates, amino acids, terpenes or steroids - the so-called chiral pool -has its limitations. According to a survey from 1984 [78] only about 10-20% of compounds are available from the chiral pool at an affordable price in the range of US 100-250 per kg. Considering the above-mentioned problems with the alternative ways of obtaining enantiomerically pure compounds, it is obvious that enzymatic methods represent a valuable addition to the existing toolbox available for the asymmetric synthesis of fine chemicals [79]. 

There are certainly some drawbacks worthy of mention for a chemist intent on using biocatalysts  

Since there is no general way of creating mirror-image enzymes from d amino acids, it is impossible to invert the chiral induction of a given enzymatic reaction 

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The disadvantages of biocatalysts will now be considered, followed by their advantages. You should note that the pros and cons of biotechnology versus chemical synthesis are very general and that exceptions may exist. 

Apart from economic considerations, the inherent disadvantages of biocatalysts have also limited the transformation of new technologies into industrial processes. Table 2.3 lists the major drawbacks of bioprocesses. 

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